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  • Other Sources  (69)
  • Chichester, UK  (27)
  • Cambridge University Press
  • Institut für Meereskunde Kiel
  • 2020-2022  (29)
  • 1980-1984  (36)
  • 1950-1954  (2)
  • 1920-1924  (2)
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Keywords
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Year
  • 1
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    Seismic Wave Propagation in Stratified Media (1983)
    Cambridge University Press
    In:  Cambridge, 342 pp., Cambridge University Press, vol. 13, no. XVI:, pp. 227-235, (ISBN 3-540-43528-X)
    Details
    Publication Date: 1983
    Keywords: Textbook of geophysics ; Seismology ; Seismics (controlled source seismology) ; Waves
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    A Treatise on the Theory of Bessel Functions (1922)
    Cambridge University Press
    In:  Cambridge, Cambridge University Press, vol. 10, no. 1, pp. 1-40, (ISBN: 0-08-040286-0)
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    Publication Date: 1922
    Keywords: Textbook of mathematics
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    BIBLIOGRAPHY SEISMOLOGY
  • 3
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    Exploration Seismology Vol. 1, History, Theory and Data Acquisition (1982)
    Cambridge University Press
    In:  Boston, 227 pp., Cambridge University Press, vol. Developments in Petroleum Science vol. 15B, no. Publ. No. 12, pp. 9, (ISBN 0-521-66023-8 hc (0-521-66953-7 pb))
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    Publication Date: 1982
    Keywords: Textbook of geophysics ; Seismics (controlled source seismology)
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    BIBLIOGRAPHY SEISMOLOGY
  • 4
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    Exploration Seismology Vol. 2, Data-Processing and Interpretation (1983)
    Cambridge University Press
    In:  Boston, 227 pp., Cambridge University Press, vol. Developments in Petroleum Science vol. 15B, no. Publ. No. 12, pp. 9, (ISBN 0-521-66023-8 hc (0-521-66953-7 pb))
    Details
    Publication Date: 1983
    Keywords: Textbook of geophysics ; Seismics (controlled source seismology)
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    BIBLIOGRAPHY SEISMOLOGY
  • 5
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    Male reproductive maturity in the octopus, Eledone cirrhosa (Cephalopoda: Octopoda) (1984)
    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 64 . pp. 573-579.
    Details
    Publication Date: 2020-07-16
    Description: Males of Eledone cirrhosa grow to a size little over 600 g and normally have well-developed, and presumably active, reproductive organs from about 200 g upwards. Total weight of the genital bag is well correlated with total body weight (r= 0·906). Growth of the testis precedes that of the spermatophoric sac, and the size of neither of these reproductive components is predictable from body weight. The sizes of these organs and the estimated number and length of stored spermatophores are given for 100 g intervals of total body weight. No evidence was obtained for a seasonal trend in male maturity.
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  • 6
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    The abundance of Octopus in the English Channel (1954)
    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 33 (02). pp. 515-536.
    Details
    Publication Date: 2020-09-09
    Description: During 1950, the Common Octopus (Octopus vulgaris Lamarck) was to be found along the south coast of England in greater numbers than at any time since Garstang (1900) reported on the ‘plague’ on the coasts of Devon and Cornwall in 1899–1900. In earlier papers (Rees, 1950, 1952) the distribution of the octopus in our northern waters was reviewed, and it was demonstrated that this species is an immigrant which breeds on our south coast only rarely. It reaches these coasts by being brought there as a planktonic larva by the water circulation in the English Channel and by migrations of the adult. The most important factor in controlling the movements of the adult, however, might be expected to be the water temperature in the English Channel—where the species is at the northern limit of its breeding range and might therefore be extremely sensitive to slight changes in temperature.
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  • 7
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    Zoning in highly alkaline magma bodies (1984)
    Cambridge University Press
    In:  Geological Magazine, 121 (6). pp. 563-575.
    Details
    Publication Date: 2020-07-31
    Description: We present chemical data on magmatically heterogeneous pyroclastic deposits of late Quaternary age erupted from zoned magma systems underlying Tenerife (Canary Islands), Sao Miguel and Faial (Azores), and Vesuvius. The most fractionated magmas present at each centre are respectively Na-rich phonolite, trachyte, and K-rich phonolite. Within any one deposit, chemical variation is either accompanied by changes in the phenocryst assemblage (petrographic zonation) or is largely manifested in trace element abundances, unaccompanied by any petrographic change (occult zonation). Zoning is analogous to that in calc-alkaline systems where the most fractionated products are high-silica rhyolites. When a range of magma types are considered, a correlation emerges between roofward depletion of trace elements (especially REE) in the zoned system and compatability of those same trace elements in the accessory phenocryst phases present. Thus, allanite- or chevkinite-bearing rhyolitic systems are light-REE depleted roofwards, the sphene-bearing Tenerife system is middle-REE depleted roofwards, the melanite-bearing Vesuvius system is heavy-REE depleted roofwards, while the Azores systems, which lack these phases, display roofward REE enrichment. Therefore, the behaviour of trace elements may in each case be explained by fractionation of observed phenocryst assemblages. The resemblance between features of zoned magma systems and published work on the dynamic consequences of cooling saturated aqueous solutions prompts us to suggest that sidewall crystallization and consequent boundary-layer uprise to form a capping layer at top of the system may be a plausible mechanism for the generation of both petrographic and occult zonation. Reverse zoning occurs among the first-erupted tephra of some deposits, demonstrating that the most highly differentiated magma available is not always the first to be tapped during an eruption from a zoned system.
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  • 8
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    The female reproductive cycle of the octopus, Eledone cirrhosa (1983)
    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 63 . pp. 71-83.
    Details
    Publication Date: 2020-07-16
    Description: Changes in the relative size of the ovary, oviducal glands and eggs are described for Eledone cirrhosa captured from the North Sea off Aberdeen over a 3 year period (N = 488). The analysis is based only on freshly caught animals, excluding those held in aquarium conditions (〉 5 days). Ovary enlargement and egg size estimates are used as indices of sexual maturity. Between 0–15% and 18–95% of total body weight is contributed by the ovary. Maximum egg length in the ovary ranges up to 7 mm. On these criteria, sexual maturation typically occurs at body sizes between 400–1000 g although some animals of 1000–1200 g are found showing no evidence of ovary enlargement. The majority of the monthly sample is always immature but maturation can apparently occur at almost any time of the year. Increase in mean ovary index and mean values for egg size are strongly seasonal and indicate a peak incidence of sexual maturity over 2–3 months in the July-September period. Spawning is presumed to follow within 1 month. Estimates of the fecundity of the females, based on the egg sample from the ovary, range from 2·2 × 103 to 55 × 10 3 eggs with a mean of 11 × 10 3 and a mode of 7·5 × 10 3 eggs.
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  • 9
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    Reproductive maturity in fresh and aquarium-held Eledone cirrhosa (Cephalopoda: Octopoda) (1984)
    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 64 . pp. 581-585.
    Details
    Publication Date: 2020-07-16
    Description: Female Eledone cirrhosa held in aquarium conditions for periods of time of five daysand over show relatively enlarged ovary sizes. Values for ovary index considerably exceed thoseof freshly caught animals and the incidence of the final stage of maturity, in which eggs pack the oviducts, is greater. A comparison of maturity indices for fresh and aquarium males was inconclusive. The range of factors associated with aquarium conditions is briefly reviewed and it is concluded that studies of cephalopod reproductive maturation must distinguish fresh and aquarium animals. Introduction External factors effective in inducing sexual maturation in cephalopods have been suggested several times. The influence of the absence of light has been implicated since the experiments of Wells & Wells (1959) showed that blinded Octopus vulgar is matured precociously. An effect of short day length in stimulating the optic glands of Sepia has been found by Defretin & Richard (1967) and Richard (1967) but this is not clearly the case for Octopus (Buckley, 1977). Octopuses kept in aquarium conditions for lengthy periods are said to have larger relative gonad sizes than those fresh from the sea (Wells & Wells, 1975). One of the factors associated with aquarium conditions is often a degree of starvation, and this circumstance alone is held to be a factor in inducing precocious sexual maturation in Eledone (Mangold & Boucher-Rodoni, 1973). In the course of recent studies on the growth and reproduction of Eledone cirrhosa from the North Sea (Boyle & Knobloch, 1982,1983,1984) animals which had remained in aquarium conditions for 5 days or over were separated from the analysis.
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  • 10
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    The biology of Isancistrum subulatae n.sp., a monogenean parasitic on the squid, Alloteuthis subulata, at Plymouth (1984)
    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 64 (02). pp. 285-302.
    Details
    Publication Date: 2020-07-16
    Description: A new species of a monogenean Isancistrum subulatae (Gyrodactylidae) has been discovered on the arms and tentacles of the cephalopod mollusc Alloteuthis subulata at Plymouth and I. loliginis, on the gills of the same host, has been re-discovered for the first time since its original description in 1912. I. subulatae, like other gyrodactylids, is viviparous, and has been shown by experiments to transfer to new hosts by contagion. In nature such transfers probably take place during copulation of the hosts and since the parasite may occur in numbers of several thousands per host, it may thereby constitute a venereal disease.
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  • 11
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    The Distribution of Octopus Vulgaris Lamarck in British Waters (1950)
    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 29 (02). pp. 361-378.
    Details
    Publication Date: 2020-09-10
    Description: In Britain Octopus vulgaris occurs on the Channel coast and only very rarely on other coasts. In Brittany and the Channel Islands it frequently makes its lair at low water, but on the English side of the Channel it does not come so close inshore except in abnormal years of high sea temperatures. The discovery of Octopus larvae of various sizes, from newly hatched to 6·0 mm. (mantle length), in plankton hauls taken to the north of the Channel Islands, proves that the species has a much longer planktonic life than hitherto supposed. The water circulation in the English Channel, as indicated by drift bottles, is admirably suited to the dispersal of larvae to our shores from breeding centres on the coasts of Brittany and the Channel Islands.
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  • 12
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    On growth of the octopus Eledone cirrhosa (1982)
    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 62 (2). pp. 277-296.
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    Publication Date: 2020-07-16
    Description: The growth of the octopus Eledone cirrhosa has been studied in a population from the North Sea off Aberdeen. Data are presented for the growth of individuals isolated in aquarium conditions; the growth of size classes in thefieldpopulation; and preliminary information on the growth relationships of gonad, somatic, cardiac and brain components of the body. At 15 °C Eledone cirrhosa is capable of growing from 10 to 1000 g in 270 days. From octopuses which feed readily in captivity, weight specific growth rates of up to about 3–5 % day-1 for animals of 100 g body weight are recorded, falling to a maximum of about 1–5 % day-1 at body sizes above 500 g. Females stop growing when sexually mature, but in the sample captured they were consistently larger than males, a feature which may account for the 7:1 bias towards the incidence of females. On a wet-weight basis, the mean food incorporation into growth is 37 % of the food ingested, which is 49% of the gross weight of crabs killed. Field data for 1978/79 suggest that animals recruited to the population at the beginning of the year grew steadily until December, overwintered without growing, then grew rapidly for several months in the subsequent year before disappearing from the samples. The estimated average age of those animals and by implication, the life span, is 20 months.
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  • 13
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    Effects of variations in light intensity on life processes of the planktonic foraminifer Globigerinoides Sacculifer in laboratory culture (1981)
    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom UK, 62 . pp. 435-451.
    Details
    Publication Date: 2020-07-27
    Description: The planktonic foraminifer Globigerinoides sacculifer (Brady) was cultured under two different light intensities and in continuous darkness. High light intensity (HLI = 4oo-soo einsteins/m2/s) resulted in a longer lifespan, a greater number of chambers formed, and a larger final shell size compared with individuals cultured under low light intensity (LLI = 20-50 einsteins/m2/s) or in continuous darkness. Shell growth rates were unaffected by increasing light intensity, but gametogenesis was delayed. Continuous darkness induced a rapid onset of gametogenesis in organisms with shell lengths larger than 250 m. Feeding frequency had a greater effect on growth and reproduction than light intensity under conditions of LLI and HLI, but continuous darkness had an overriding effect on growth and reproduction owing to the rapid onset of gametogenesis which terminated the life of the mother cell. Our previous data indicated that the longevity of G. sacculifer was dependent on feeding frequency, and that G. sacculifer cultured under LLI had a lifespan of approximately 2-4 weeks. Present results suggest that the lifespan can vary from a minimum of 8 days for organisms fed daily in continuous darkness to a maximum of 54 days for organisms fed once every 7 days and maintained in HLI. It is concluded that individual G. sacculifer attain a shell size greater than 6oo ,urn only if they maintain their position in the euphotic zone. Prolonged existence below the euphotic zone would result in premature death or gametogenesis following stunted shell growth.
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  • 14
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    Messungen zum Widerstandsbeiwert von Verankerungskomponenten = Measurements of mooring component drag coefficients (1984)
    Institut für Meereskunde Kiel
    In:  (Diploma thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 96 pp . Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 129 . DOI 10.3289/ifm_ber_129 〈http://dx.doi.org/10.3289/ifm_ber_129〉.
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    Publication Date: 2013-07-31
    Type: Thesis , NonPeerReviewed
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  • 15
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    Wind-, Temperatur- und Feuchteprofile über der Kieler Bucht im Zeitraum April bis Oktober 1977 (1980)
    Institut für Meereskunde Kiel
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 077 (90). Institut für Meereskunde Kiel, Kiel, Germany, 73 pp.
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    Publication Date: 2013-07-24
    Type: Report , NonPeerReviewed
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  • 16
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    Beobachtungen und erste Ergebnisse der "Meteor"-Reise 56 aus der Scotia-See und der Bransfield-Straße im November/Dezember 1980 (ANT I): ein nautischer und wissenschaftlicher Bericht (1981)
    Institut für Meereskunde Kiel
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 080 . Institut für Meereskunde Kiel, pp. 1-120, 120 pp.
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    Publication Date: 2016-03-18
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  • 17
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    Current and temperature measurements in the North-East Atlantic during NEADS : a data report (1981)
    Institut für Meereskunde Kiel
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 090 (90). Institut für Meereskunde Kiel, Kiel, Germany, 100 pp.
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    Publication Date: 2012-07-06
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  • 18
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    CTD measurements made from F.S. POSEIDON during JASIN nineteen hundred and seventy-eight : a data report (1982)
    Institut für Meereskunde Kiel
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 097 (90). Institut für Meereskunde Kiel, Kiel, Germany, 180 pp.
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    Publication Date: 2012-07-06
    Type: Report , NonPeerReviewed
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  • 19
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    Biological Studies of the Exploited Stock ofLoligo Forbesi (Mollusca: Cephalopoda) in the Azores (1982)
    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 62 (04). p. 799.
    Details
    Publication Date: 2020-07-16
    Description: Five hundred and twenty-eight specimens of Loligo forbesi Steenstrup, from landings in Horta, Faial, Azores, during the year 1 March 1980 to 28 February 1981, were tudied; 59·3 % were males, 40·7 % females. Of the males 80·2 % were sexually mature, of the females 91·6 %, both sexes showing the highest degree of maturity in spring and he lowest in autumn. The mean dorsal mantle length of the mature males was 56·5 cm, or females 33·5 cm. A weight-length relationship was calculated. he stomachs of 622 specimens were sampled, of which 306 contained food. The prey omponents were studied qualitatively. The main prey was fish (82·0%), of which 0·5 % were horse mackerel, Trachurus picturatus, this being the most important food rganism. Preliminary results of statolith readings are given.
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  • 20
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    The Light Organs of Sepiola Atlantica and Spirula Spirula (Mollusca: Cephalopoda): Bacterial and Intrinsic Systems in The Order Sepioidea (1981)
    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 61 (04). pp. 901-916.
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    Publication Date: 2020-07-16
    Description: Symbiotic luminous bacteria have been described in, and cultured from, a number of species offish and cephalopod. Indeed only in these two groups are extracellular luminous bacteria believed to be utilized as a source of light (see Buchner (1965) and Herring (1978) for references). Despite several earlier investigations of such symbioses in cephalopods the bacteria in these animals have not been adequately identified, nor has the extent of their role been clarified. The ultrastructural relationships between bacteria and the tissues of the squid accessory nidamental gland have been investigated in the non-luminous species Loligo pealei (Lesueur) (Bloodgood, 1977) and Sepia officinalis L. (Van den Branden et al. 1979) but no comparative work on luminous species has been undertaken apart from that on Heteroteuthis dispar (Rüppell), whose photophore does not contain typical luminous bacteria (Dilly & Herring, 1978; cf. Leisman, Cohn & Nealson, 1980). The order Sepioidea contains five families, among which are the two families Sepiolidae and Spirulidae. Though the presence of luminous bacteria is known in some sepiolids (as well as in certain loliginids (order Teuthoidea)) some doubt remains about the source of light in the photophore of Spirula spirula Hoyle. The steady luminescence of this species has prompted speculation that bacteria may be involved (Harvey, 1952). In this paper we compare the anatomy and ultrastructure of the photophores of both Sepiola and Spirula in order to clarify some of these problems.
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  • 21
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    Cephalopod Beaks from the Stomachs of Two Northern Bottlenosed Whales (Hyperoodon Ampullatus) (1980)
    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 60 (01). p. 151.
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    Publication Date: 2020-07-16
    Description: This is the first detailed analysis of cephalopod beaks from the stomach of a northern bottlenosed whale, Hyperoodon ampullatus (Forster, 1770). The digestive action of many predators barely affects the chitinous beaks of cephalopods and some cetaceans accumulate the beaks in considerable numbers in their stomachs. The present beaks are clean and unbroken. Identification of cephalopod beaks from stomachs of predators such as sperm whales (see Clarke, 1977), seals (Clarke & Trillmich, 1980) and albatrosses (Clarke, Croxall & Prince, 1980) throws considerable light on the biology and relative ecological importance of the species of cephalopods concerned as well as providing useful information on the diet of the predators.
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  • 22
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    The GATE Lagrangian Batfish experiment : Summary report (1981)
    Institut für Meereskunde Kiel
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 088 (90). Institut für Meereskunde Kiel, Kiel, Germany, 170 pp.
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    Publication Date: 2012-07-06
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  • 23
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    Die Variabilität der Phytoplanktonschichtung in driftenden Wasserkörpern : Untersuchungen aus dem Skagerrak, Kattegat und Bornholm-Becken im März 1979 (1982)
    Institut für Meereskunde Kiel
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 098 (90). Institut für Meereskunde Kiel, Kiel, Germany, 132 pp.
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    Publication Date: 2012-07-06
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  • 24
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    Der Zustand der Fischbestände in der Schlei und die Entwicklung der Fischerei im Zeitraum 1962-1981 (1981)
    Institut für Meereskunde Kiel
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 091 . Institut für Meereskunde Kiel, Kiel, Germany, 89 pp.
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    Publication Date: 2019-07-26
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  • 25
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    Untersuchung bodennaher Temperatur- und Windfelder im Übergangsbereich Land-See am Beispiel der Kieler Bucht (1981)
    Institut für Meereskunde Kiel
    In:  (PhD/ Doctoral thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 93 pp . Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 092 . DOI 10.3289/IFM_BER_92 〈http://dx.doi.org/10.3289/IFM_BER_92〉.
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    Publication Date: 2013-07-25
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  • 26
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    Fucus vesiculosus als Schwermetall-Bioakkumulator: der Einfluss von Temperatur, Salzgehalt und Metallkombination auf die Inkorporationsleistung (1981)
    Institut für Meereskunde Kiel
    In:  (PhD/ Doctoral thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 54 pp . Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 093 . DOI 10.3289/IFM_BER_93 〈http://dx.doi.org/10.3289/IFM_BER_93〉.
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    Publication Date: 2013-07-25
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  • 27
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    The warmwatersphere of the Northeast Atlantic : a miscellany (1984)
    Institut für Meereskunde Kiel
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 128 . Institut für Meereskunde Kiel, Kiel, Germany, 39 pp.
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    Publication Date: 2013-07-31
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  • 28
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    Verhalten der Freifallprofilsonde FPS = Response of the free-fall profiler FPS (1984)
    Institut für Meereskunde Kiel
    In:  (Diploma thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 68 pp . Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 135 . DOI 10.3289/ifm_ber_135 〈http://dx.doi.org/10.3289/ifm_ber_135〉.
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    Publication Date: 2013-05-22
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  • 29
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    Oxygen depletion 1980 - 1983 in coastal waters of the Federal Republic of Germany (1984)
    Institut für Meereskunde Kiel
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 130 . Institut für Meereskunde Kiel, Kiel, Germany, 87 pp.
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    Publication Date: 2018-04-09
    Type: Report , NonPeerReviewed
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    Gemeinschaftsstrukturen, Abundanz, Biomasse und Produktion des Makrozoobenthos sandiger Böden der Kieler Bucht in 5-15m Wassertiefe = Community-structures, abundance, biomass and production of macrozoobenthos inhabiting sandy bottoms of Kiel Bay in 5-15m waterdepth (1984)
    Institut für Meereskunde Kiel
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 123 . Institut für Meereskunde Kiel, Kiel, Germany, 124 pp.
    Details
    Publication Date: 2013-11-19
    Type: Report , NonPeerReviewed
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    Statoliths of one fossil and four living squids (Gonatidae: Cephalopoda) (1980)
    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 60 (02). p. 329.
    Details
    Publication Date: 2020-07-16
    Description: Cephalopod statoliths are paired calcareous stones which lie in cavities, the statocysts, within the skull. They have a form which, though variable, shows promise as a source of criteria for taxonomic and evolutionary studies. As a preliminary to more detailed studies, Clarke (1978) published a description of the form of a generalized teuthoid statolith, coined nomenclature for the various parts and gave a very brief survey of variation of statoliths within the living Cephalopoda. This nomenclature was used in a detailed description of fossilized teuthoid statoliths by Clarke & Fitch (1979). Here, descriptions of the statoliths of the living species Berryteuthis magister (Berry, 1913), Gonatopsis borealis Sasaki, 1923, Gonatopsis (Boreoteuthis) makko Okutani & Nemoto, 1964 and Gonatus fabricii (Lichtenstein, 1818) are given and the fossil Berryteuthis species described in outline by Clarke & Fitch (1979) is compared with B. magister. A statistical analysis of measurements of the statoliths of these five species has been made and the results are presented. This forms the first part of a general description of teuthoid statoliths and similar studies on the Ommastrephidae and the Loliginidae are in preparation.
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    THE INTCAL20 NORTHERN HEMISPHERE RADIOCARBON AGE CALIBRATION CURVE (0–55 CAL kBP) (2020)
    Department of Geosciences, University of Arizona | Cambridge University Press
    In:  Radiocarbon, 62 (4). pp. 725-757.
    Details
    Publication Date: 2021-01-08
    Description: Radiocarbon (14C) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating for fluctuations in atmospheric 14C concentration. Although calibration curves are constructed from independently dated archives, they invariably require revision as new data become available and our understanding of the Earth system improves. In this volume the international 14C calibration curves for both the Northern and Southern Hemispheres, as well as for the ocean surface layer, have been updated to include a wealth of new data and extended to 55,000 cal BP. Based on tree rings, IntCal20 now extends as a fully atmospheric record to ca. 13,900 cal BP. For the older part of the timescale, IntCal20 comprises statistically integrated evidence from floating tree-ring chronologies, lacustrine and marine sediments, speleothems, and corals. We utilized improved evaluation of the timescales and location variable 14C offsets from the atmosphere (reservoir age, dead carbon fraction) for each dataset. New statistical methods have refined the structure of the calibration curves while maintaining a robust treatment of uncertainties in the 14C ages, the calendar ages and other corrections. The inclusion of modeled marine reservoir ages derived from a three-dimensional ocean circulation model has allowed us to apply more appropriate reservoir corrections to the marine 14C data rather than the previous use of constant regional offsets from the atmosphere. Here we provide an overview of the new and revised datasets and the associated methods used for the construction of the IntCal20 curve and explore potential regional offsets for tree-ring data. We discuss the main differences with respect to the previous calibration curve, IntCal13, and some of the implications for archaeology and geosciences ranging from the recent past to the time of the extinction of the Neanderthals.
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    Marine20—The Marine Radiocarbon Age Calibration Curve (0–55,000 cal BP) (2020)
    Department of Geosciences, University of Arizona | Cambridge University Press
    In:  Radiocarbon, 62 (4). pp. 779-820.
    Details
    Publication Date: 2021-01-08
    Description: The concentration of radiocarbon (14C) differs between ocean and atmosphere. Radiocarbon determinations from samples which obtained their 14C in the marine environment therefore need a marine-specific calibration curve and cannot be calibrated directly against the atmospheric-based IntCal20 curve. This paper presents Marine20, an update to the internationally agreed marine radiocarbon age calibration curve that provides a non-polar global-average marine record of radiocarbon from 0–55 cal kBP and serves as a baseline for regional oceanic variation. Marine20 is intended for calibration of marine radiocarbon samples from non-polar regions; it is not suitable for calibration in polar regions where variability in sea ice extent, ocean upwelling and air-sea gas exchange may have caused larger changes to concentrations of marine radiocarbon. The Marine20 curve is based upon 500 simulations with an ocean/atmosphere/biosphere box-model of the global carbon cycle that has been forced by posterior realizations of our Northern Hemispheric atmospheric IntCal20 14C curve and reconstructed changes in CO2 obtained from ice core data. These forcings enable us to incorporate carbon cycle dynamics and temporal changes in the atmospheric 14C level. The box-model simulations of the global-average marine radiocarbon reservoir age are similar to those of a more complex three-dimensional ocean general circulation model. However, simplicity and speed of the box model allow us to use a Monte Carlo approach to rigorously propagate the uncertainty in both the historic concentration of atmospheric 14C and other key parameters of the carbon cycle through to our final Marine20 calibration curve. This robust propagation of uncertainty is fundamental to providing reliable precision for the radiocarbon age calibration of marine based samples. We make a first step towards deconvolving the contributions of different processes to the total uncertainty; discuss the main differences of Marine20 from the previous age calibration curve Marine13; and identify the limitations of our approach together with key areas for further work. The updated values for ΔR, the regional marine radiocarbon reservoir age corrections required to calibrate against Marine20, can be found at the data base http://calib.org/marine/.
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  • 34
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    Langfristige Veränderungen in der Verbreitung von Nordseefischen, untersucht durch Korrelations- und Varianzanalyse (1980)
    Institut für Meereskunde Kiel
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 076 (90). Institut für Meereskunde Kiel, Kiel, Germany, 145 pp.
    Details
    Publication Date: 2012-07-06
    Type: Report , NonPeerReviewed
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    The GATE Lagrangian Batfish experiment: Data report,10: MAP 3L1 (1981)
    Institut für Meereskunde Kiel
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 089A (90). Institut für Meereskunde Kiel, Kiel, Germany, 119 pp.
    Details
    Publication Date: 2012-07-06
    Type: Report , NonPeerReviewed
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    Über den Monsunresponse der Zirkulation im westlichen äquatorialen Indischen Ozean (1982)
    Institut für Meereskunde Kiel
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 099 (90). Institut für Meereskunde Kiel, Kiel, Germany, 153 pp.
    Details
    Publication Date: 2012-07-06
    Type: Report , NonPeerReviewed
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    Wassermassenanalyse im tropischen und subtropischen Nordostatlantik = Analysis of watermasses in the tropical and subtropical north-east Atlantic (1982)
    Institut für Meereskunde Kiel
    In:  (Diploma thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 72 pp . Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 096 (90). DOI 10.3289/IFM_BER_96 〈http://dx.doi.org/10.3289/IFM_BER_96〉.
    Details
    Publication Date: 2013-05-17
    Type: Thesis , NonPeerReviewed
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    CTD-data from the North Canary basin : "Poseidon" cruise 86,2 [POS86/2], 26 March - 13 April, 1982 (1982)
    Institut für Meereskunde Kiel
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 103 (90). Institut für Meereskunde Kiel, Kiel, Germany, 130 pp.
    Details
    Publication Date: 2014-12-12
    Type: Report , NonPeerReviewed
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  • 39
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    The GATE Lagrangian Batfish experiment: Data report,11: MAP 3L2 (1981)
    Institut für Meereskunde Kiel
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 089C (90). Institut für Meereskunde Kiel, Kiel, Germany, 136 pp.
    Details
    Publication Date: 2012-07-06
    Type: Report , NonPeerReviewed
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  • 40
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    The GATE Lagrangian Batfish experiment: Data report,12: MAP 3L3 (1981)
    Institut für Meereskunde Kiel
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 089B (90). Institut für Meereskunde Kiel, Kiel, Germany, 218 pp.
    Details
    Publication Date: 2012-07-06
    Type: Report , NonPeerReviewed
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  • 41
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    Blue-Green algae agglomeration in surface water: a microbiotope of high bacterial activity (1981)
    Institut für Meereskunde Kiel
    Details
    Publication Date: 2022-02-10
    Description: European Marine Biology Symposium. 15 1981 Abstract Mass accumulations of filamentous blue-green algae in surface waters of the Baltic Sea cause patches of high bacterial productivity within water masses of low microbial activity. Since these algae are apparently not grazed by zooplankton organisms, their degradation in the surface water layer is mainly due to associated bacteria. The network of algae filaments attracts a wide range of small organisms including rotifers, crustaceans, ciliates and flagellates, resulting in a microbiotope of considerable complexity. The succession of bacterial colonization of Nodularia spumigena and the activity state of the community was investigated by the INT-staining technique and by microautoradiography. The excretion rates of photosynthesized matter by the bluegreen algae agglomerates indicate a high rate of transfer of substrate towards the adherent heterotrophic bacteria. The fate and the final involvement of the agglomerates in the food chain are discussed.
    Type: Article , NonPeerReviewed
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  • 42
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    Glaciation in South Africa, Australia, and Tasmania (1923)
    Cambridge University Press
    Details
    Publication Date: 2022-02-17
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  • 43
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    Formation and maintenance of subsiding shells around non‐precipitating and precipitating cumulus clouds (2021)
    John Wiley & Sons, Ltd | Chichester, UK
    Details
    Publication Date: 2021-07-20
    Description: A shell of subsiding air is generally known to develop around cumulus clouds and shield them from their environment. We seek here to improve our understanding of such shells by (a) revealing the detailed vertical and horizontal structure of shells surrounding both shallow and deeper clouds, and (b) identifying the mechanisms responsible for in‐shell subsidence generation and maintenance. To that end, a high‐resolution Cloud Resolving Model simulation of the shallow‐to‐deep convection transition over a tropical land surface is analysed with an emphasis on the cloud's near environment. Shells surrounding shallow and deep clouds are found to possess surprisingly similar characteristics. However important differences are observed near cloud top where the deepest clouds are associated with stronger subsidence and broader shells. In the convective outflow region, stronger in‐shell subsidence coincides with strong buoyancy reversal, but also with strong pressure gradients naturally generated by cloud‐top vortex dynamics. A more delicate balance between various processes takes place below, and in‐shell subsidence is only barely sustained as buoyancy reversal is largely compensated by pressure gradients. Finally, while evaporation is clearly the main source of buoyancy reversal everywhere around cloud edges, it is also shown that the downward transport of warmer air from aloft through the subsiding shells may compensate for evaporative cooling to slowly bring in‐shell buoyancy to a near‐neutral state. Overall, while it cannot be denied that evaporative cooling and buoyancy reversal play important roles in generating and sustaining in‐shell subsidence, the present results also emphasise that mechanical forcing at cloud top and downward transport within the shells should not be overlooked.
    Description: Narrow “shells” of subsiding air generally form around cumulus clouds, but the mechanisms responsible for their formation and maintenance are still debated. In this study, the dynamics of these shells is investigated using a high‐resolution simulation of idealized tropical convection. It is shown that in‐shell subsiding motions are generally driven by buoyancy reversal. However, mechanical forcing contributes at least equally at the top of all convective clouds. In addition, it is found that buoyancy reversal due to evaporative cooling may be offset by the downward transport of warmer air from aloft through the subsiding shells.
    Keywords: 551.5 ; cloud dynamics ; near‐cloud environment ; subsiding shells ; tropical convection
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    An application of WKBJ theory for triad interactions of internal gravity waves in varying background flows (2021)
    John Wiley & Sons, Ltd | Chichester, UK
    Details
    Publication Date: 2021-07-20
    Description: Motivated by the question of whether and how wave–wave interactions should be implemented into atmospheric gravity‐wave parametrizations, the modulation of triadic gravity‐wave interactions by a slowly varying and vertically sheared mean flow is considered for a non‐rotating Boussinesq fluid with constant stratification. An analysis using a multiple‐scale WKBJ (Wentzel–Kramers–Brillouin–Jeffreys) expansion identifies two distinct scaling regimes, a linear off‐resonance regime, and a nonlinear near‐resonance regime. Simplifying the near‐resonance interaction equations allows for the construction of a parametrization for the triadic energy exchange which has been implemented into a one‐dimensional WKBJ ray‐tracing code. Theory and numerical implementation are validated for test cases where two wave trains generate a third wave train while spectrally passing through resonance. In various settings, of interacting vertical wavenumbers, mean‐flow shear, and initial wave amplitudes, the WKBJ simulations are generally in good agreement with wave‐resolving simulations. Both stronger mean‐flow shear and smaller wave amplitudes suppress the energy exchange among a resonantly interacting triad. Experiments with mean‐flow shear as strong as in the vicinity of atmospheric jets suggest that internal gravity‐wave dynamics are dominated in such regions by wave modulation. However, triadic gravity‐wave interactions are likely to be relevant in weakly sheared regions of the atmosphere.
    Description: This study explores wave–wave interactions of modulated internal gravity waves (GWs) in varying background flows using WKBJ techniques. The resulting ray‐tracing model (b) is compared to wave‐resolving LES (a). As a key result, we find that wave modulation partially suppresses the energy exchange in triadic GW interactions, and thus triadic GW interactions are likely to be relevant in weakly sheared regions of the atmosphere.
    Description: German Research Foundation (DFG) US National Science Foundation
    Keywords: 551.5 ; internal gravity waves ; parametrization ; ray‐tracing ; triadic wave–wave interaction ; wave modulation
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    Extreme precipitation events in the Mediterranean: Spatiotemporal characteristics and connection to large‐scale atmospheric flow patterns (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-07-01
    Description: The Mediterranean region is strongly affected by extreme precipitation events (EPEs), sometimes leading to severe negative impacts on society, economy, and the environment. Understanding such natural hazards and their drivers is essential to mitigate related risks. Here, EPEs over the Mediterranean between 1979 and 2019 are analysed, using ERA5, the latest reanalysis dataset from ECMWF. EPEs are determined based on the 99th percentile of their daily distribution (P99). The different EPE characteristics are assessed, based on seasonality and spatiotemporal dependencies. To better understand their connection to large‐scale atmospheric flow patterns, Empirical Orthogonal Function analysis and subsequent non‐hierarchical K‐means clustering are used to quantify the importance of weather regimes to EPE frequency. The analysis is performed for different variables, depicting atmospheric variability in the lower and middle troposphere. Results show a clear spatial division in EPE occurrence, with winter and autumn being the seasons of highest EPE frequency for the eastern and western Mediterranean, respectively. There is a high degree of temporal dependencies with 20% of the EPEs (median value based on all studied grid cells), occurring up to 1 week after a preceding P99 event at the same location. Local orography is a key modulator of the spatiotemporal connections and substantially enhances the probability of co‐occurrence of EPEs even for distant locations. The clustering clearly demonstrates the prevalence of distinct synoptic‐scale atmospheric conditions during the occurrence of EPEs for different locations within the region. Results indicate that clustering, based on a combination of sea level pressure (SLP) and geopotential height at 500 hPa (Z500), can increase the conditional probability of EPEs by more than three (3) times (median value for all grid cells) from the nominal probability of 1% for the P99 EPEs. Such strong spatiotemporal dependencies and connections to large‐scale patterns can support extended‐range forecasts.
    Description: This study analyses the spatiotemporal characteristics of extreme precipitation events over the Mediterranean, and their connection to large‐scale atmospheric flow patterns. It is shown that by conditioning the extremes based on the atmospheric variability in the low‐ and mid‐troposphere, their probability increases more than threefold, when using nine clusters to group all the synoptic daily patterns. This finding can support extended‐range forecasts, as for such lead times the NWP models are more skillful in predicting large‐scale patterns than localized extremes.
    Description: Marie Skłodowska‐Curie
    Description: European Union's Horizon 2020
    Keywords: 551.6 ; extreme precipitation ; large‐scale/circulation patterns ; Mediterranean ; weather regimes
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    SAD: Verifying the scale, anisotropy and direction of precipitation forecasts (2021)
    John Wiley & Sons, Ltd | Chichester, UK
    Details
    Publication Date: 2021-07-20
    Description: One important attribute of meteorological forecasts is their representation of spatial structures. While several existing verification methods explicitly measure a structure error, they mostly produce a single value with no simple interpretation. Extending a recently developed wavelet‐based verification method, this study separately evaluates the predicted spatial scale, orientation and degree of anisotropy. The scale component has been rigorously tested in previous work and is known to assess the quality of a forecast similar to other, established methods. However, directional aspects of spatial structure are less frequently considered in the verification literature. Since important weather phenomena related to fronts, coastlines and orography have distinctly anisotropic signatures, their representation in meteorological models is clearly of interest. The ability of the new wavelet approach to accurately evaluate directional properties is demonstrated using idealized and realistic test cases from the MesoVICT project. A comparison of precipitation forecasts from several forecasting systems reveals that errors in scale and direction can occur independently and should be treated as separate aspects of forecast quality. In a final step, we use the inverse wavelet transform to define a simple post‐processing algorithm that corrects the structural errors. The procedure improves visual similarity with the observations, as well as the objective scores.
    Description: Forecasts of precipitation fields are difficult to evaluate due to their complex, intermittent spatial structure. The SAD forecast verification method uses wavelets to compare the scale (colours in the top row), anisotropy (bottom, arrow length) and preferred direction (bottom, arrow angles) of simulated and observed fields. The new approach is successfully tested using data from the MesoVICT community project.
    Description: German Research Foundation (DFG)
    Keywords: 551.5 ; MesoVICT ; precipitation forecasts ; structure error ; verification ; wavelets
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    A cold pool perturbation scheme to improve convective initiation in convection‐permitting models (2021)
    John Wiley & Sons, Ltd | Chichester, UK
    Details
    Publication Date: 2021-07-20
    Description: Cold pools originate from evaporation in precipitating downdraughts and spread as density currents at the surface. Vertical motion at the leading edge of the cold pool is an important trigger for new convective cells in organised convective storms. However, these motions are poorly resolved at the grid lengths of a kilometre or more used in convection‐permitting models. Consequently, the simulated gust fronts do not trigger enough new convection, leading to precipitation deficits and a lack of convective organization. To address these deficits, we introduce a cold pool perturbation (CPP) scheme that strengthens vertical velocity at the simulated cold pool gust fronts. This is achieved by relaxing the vertical velocity in the gust front region towards a target value derived from similarity theory. Applying the CPP scheme for simulations of a highly convective 10‐day period, we find increased precipitation amplitudes during the afternoon. There is also evidence for improvements in the location of precipitation and for stronger organization of convection, although substantial errors remain. The cold pools themselves become more frequent, larger and more intense. An additional potentially beneficial influence was found for convective initiation at sea breeze fronts.
    Description: We develop a cold pool perturbation scheme which strengthens the too weak vertical velocities at cold pool gust fronts in convection‐permitting models. In so doing, cold‐pool‐driven convective initiation is enhanced and simulated precipitation improved.
    Keywords: 551.5 ; cold pools ; convective organization ; deep convection ; density currents ; gust fronts
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    Prioritizing reaches for restoration in a regulated Alpine river: Locally driven versus hydro‐morphologically based actions (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-06-27
    Description: We discuss the prioritization of river reaches to be selected for restoration measures under the constraints of financial resource limitation. We propose and apply a simple approach based on the quantification of major hydro‐morphological alterations and the critical comparison with locally proposed restoration actions. The available hydro‐morphological and ecological data for the approach do not go beyond the requirements posed by the implementation of the EU Water Framework and Floods Directives. We describe an example that refers to a heavily regulated Alpine river (Sarca River, NE Italy). The results indicate hydropower facilities as a key source of hydrological alteration, with sediment retention and grade control structures on lateral tributaries playing an additional relevant role in reducing sediment supply. The frequency and duration of sediment‐transporting floods have dramatically decreased, and the bed sediment composition has been markedly altered and become highly compacted. Habitat improvement has been achieved after the implementation of minimum environmental flows. The comparison between the results of the hydro‐morphological indicators and the locally proposed restoration actions highlights that reaches with lower degree of hydro‐morphological alterations do not coincide with the areas chosen for the locally planned actions, which often miss considerations of the relevant spatial scales. In a context of limited available financial resources and data compared to other flagship river restoration projects in the European Alps, the present work suggests viable options for the choice of target restoration reaches.
    Description: Consorzio dei Comuni BIM Sarca
    Description: Italian Ministry of Education, University and Research (MIUR)
    Description: Rete di Riserve della Sarca
    Keywords: 333.91 ; ecological flows ; hydropower ; regulated rivers ; sediment transport
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    Numerical impacts on tracer transport: A proposed intercomparison test of Atmospheric General Circulation Models (2021)
    John Wiley & Sons, Ltd | Chichester, UK
    Details
    Publication Date: 2021-07-20
    Description: The transport of trace gases by the atmospheric circulation plays an important role in the climate system and its response to external forcing. Transport presents a challenge for Atmospheric General Circulation Models (AGCMs), as errors in both the resolved circulation and the numerical representation of transport processes can bias their abundance. In this study, two tests are proposed to assess transport by the dynamical core of an AGCM. To separate transport from chemistry, the tests focus on the age‐of‐air, an estimate of the mean transport time by the circulation. The tests assess the coupled stratosphere–troposphere system, focusing on transport by the overturning circulation and isentropic mixing in the stratosphere, or Brewer–Dobson Circulation, where transport time‐scales on the order of months to years provide a challenging test of model numerics. Four dynamical cores employing different numerical schemes (finite‐volume, pseudo‐spectral, and spectral‐element) and discretizations (cubed sphere versus latitude–longitude) are compared across a range of resolutions. The subtle momentum balance of the tropical stratosphere is sensitive to model numerics, and the first intercomparison reveals stark differences in tropical stratospheric winds, particularly at high vertical resolution: some cores develop westerly jets and others easterly jets. This leads to substantial spread in transport, biasing the age‐of‐air by up to 25% relative to its climatological mean, making it difficult to assess the impact of the numerical representation of transport processes. This uncertainty is removed by constraining the tropical winds in the second intercomparison test, in a manner akin to specifying the Quasi‐Biennial Oscillation in an AGCM. The dynamical cores exhibit qualitative agreement on the structure of atmospheric transport in the second test, with evidence of convergence as the horizontal and vertical resolution is increased in a given model. Significant quantitative differences remain, however, particularly between models employing spectral versus finite‐volume numerics, even in state‐of‐the‐art cores.
    Description: The climatological and zonal mean zonal wind ū (m·s−1), as simulated by two different dynamical cores, (left) pseudospectral (GFDL‐PS) and (right) finite‐volume (CAM‐FV), with (top) 40 vertical levels and (bottom) 80 vertical levels. With higher vertical resolution, the pseudospectral core develops westerlies in the tropical stratosphere between 20 and 80 hPa, while the finite‐volume core consistently simulates easterlies at both vertical resolutions. Both cores have comparable horizontal resolution. The contour interval is 10 m·s−1.
    Description: US National Science Foundation
    Keywords: 551.5 ; age of air ; Brewer–Dobson circulation ; dynamical cores ; stratospheric dynamics ; tracer transport.
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    Extreme precipitation events over northern Italy. Part II: Dynamical precursors (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-07-20
    Description: The connection between weather extremes and Rossby wave packets (RWP) has been increasingly documented in recent years. RWP propagation and characteristics can modulate the midlatitude weather, setting the scene for temperature and precipitation extremes and controlling the geographical area affected. Several studies on extreme precipitation events (EPEs) in the Alpine area reported, as the main triggering factor, a meridionally elongated upper‐level trough as part of an incoming Rossby wave packet. In this work, we investigate a wide number of EPEs occurring between 1979 and 2015 in northern‐central Italy. The EPEs are subdivided into three categories (Cat1, Cat2, Cat3) according to thermodynamic conditions over the affected region. It is found that the three categories differ not only in terms of the local meteorological conditions, but also in terms of the evolution and properties of precursor RWPs. These differences cannot be solely explained by the apparent seasonality of the flow; therefore, the relevant physical processes in the RWP propagation of each case are further investigated. In particular, we show that RWPs associated with the strongest EPEs, namely the ones falling in Cat2, undergo a substantial amplification over the western North Atlantic due to anomalous ridge‐building 2 days before the event; arguably due to diabatic heating sources. This type of development induces a downstream trough which is highly effective in focusing water vapour transport toward the main orographic barriers of northern‐central Italy and favouring the occurrence of EPEs.
    Description: The EPEs are subdivided into three categories (Cat1, Cat2, Cat3) according to thermodynamic conditions over the affected region. The three categories not only differ locally but also in the evolution of precursor RWPs as visible in the composite Hovmöller plots. RWPs associated with the strongest EPEs, the ones falling in Cat2, undergo a substantial amplification over the west North Atlantic due to anomalous ridge‐building 2 days before the event. This type of development induces a downstream trough which is highly effective in focusing water vapour transport toward the Apennines and the Alps.
    Description: Ludwig‐Maximilians‐Universität München http://dx.doi.org/10.13039/501100005722
    Description: German Research Foundation (DFG)
    Description: Transregional Collaborative Research Centre
    Keywords: 551.6 ; atmospheric rivers ; extreme precipitation ; integrated water vapour transport ; large‐scale forcing ; potential vorticity ; Rossby wave packets
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    WRF‐based dynamical downscaling of ERA5 reanalysis data for High Mountain Asia: Towards a new version of the High Asia Refined analysis (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-07-03
    Description: The High Asia Refined analysis (HAR) is a regional atmospheric data set generated by dynamical downscaling of the Final operational global analysis (FNL) using the Weather Research and Forecasting (WRF) model. It has been successfully and widely utilized. A new version (HAR v2) with longer temporal coverage and extended domains is currently under development. ERA5 reanalysis data is used as forcing data. This study aims to find the optimal set‐up for the production of the HAR v2 to provide similar or even better accuracy as the HAR. First, we conducted a sensitivity study, in which different cumulus, microphysics, planetary boundary layer, and land surface model schemes were compared and validated against in situ observations. The technique for order preference by similarity to the ideal solution (TOPSIS) method was applied to identify the best schemes. Snow depth in ERA5 is overestimated in High Mountain Asia (HMA) and causes a cold bias in the WRF output. Therefore, we used Japanese 55‐year Reanalysis (JRA‐55) to correct snow depth initialized from ERA5 based on the linear scaling approach. After applying the best schemes identified by the TOPSIS method and correcting the initial snow depth, the model performance improves. Finally, we applied the improved set‐up for the HAR v2 and computed a one‐year run for 2011. Compared to the HAR, the HAR v2 has a better representation of air temperature at 2 m. It produces slightly higher precipitation amounts, but the spatial distribution of seasonal mean precipitation is closer to observations.
    Description: German Federal Ministry of Education and Research (BMBF) http://dx.doi.org/10.13039/501100002347
    Keywords: 551.5 ; cold bias ; dynamical downscaling ; ERA5 ; HAR ; High Mountain Asia ; snow depth ; WRF
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    Hydro Explorer: An interactive web app to investigate changes in runoff timing and runoff seasonality all over the world (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-06-27
    Description: Climatic changes and anthropogenic modifications of the river basin or river network have the potential to fundamentally alter river runoff. In the framework of this study, we aim to analyze and present historic changes in runoff timing and runoff seasonality observed at river gauges all over the world. In this regard, we develop the Hydro Explorer, an interactive web app, which enables the investigation of 〉7,000 daily resolution discharge time series from the Global Runoff Data Centre (GRDC). The interactive nature of the developed web app allows for a quick comparison of gauges, regions, methods, and time frames. We illustrate the available analytical tools by investigating changes in runoff timing and runoff seasonality in the Rhine River Basin. Since we provide the source code of the application, existing analytical approaches can be modified, new methods added, and the tool framework can be re‐used to visualize other data sets.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: WOA Institution: UNIVERSITAET POTSDAM Blended DEAL: ProjektDEAL
    Keywords: 551.488 ; global runoff database ; interactive web app ; R Shiny ; runoff seasonality ; runoff timing
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    The generalized Ekman model for the tropical cyclone boundary layer revisited: Addendum (2021)
    John Wiley & Sons, Ltd | Chichester, UK
    Details
    Publication Date: 2021-06-20
    Description: Motivated by prior research examining the myth of inertial stability as a radial restoring force in the tropical cyclone boundary layer, we explore factors determining the vertical velocity at the top of the linear vortex boundary layer. Possible applications of these findings to mature tropical cyclone vortices are discussed briefly.
    Keywords: 551.51 ; boundary layer ; generalized Ekman balance ; inertial stability ; tropical cyclones
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    Modelling and parametrization of the convective flow over leads in sea ice and comparison with airborne observations (2021)
    John Wiley & Sons, Ltd | Chichester, UK
    Details
    Publication Date: 2021-07-20
    Description: A non‐eddy‐resolving microscale model is applied to simulate convection over three different leads (elongated channels in sea ice), which were observed by aircraft over the Arctic Marginal Ice Zone in 2013. The study aims to evaluate the quality of a local and a non‐local turbulence parametrization. The latter represents a lead‐width‐dependent approach for the turbulent fluxes designed for idealised conditions of a lead‐perpendicular, near‐neutral inflow in an atmospheric boundary layer (ABL) capped by a strong inversion at around 250 to 350 m height. The observed cases considered here are also characterised by an almost lead‐perpendicular flow but, in comparison to the idealised conditions, our analysis covers effects in stable inflow conditions and a much shallower ABL. The model simulations are initialised with observed surface parameters and upwind profiles, and the results are compared with measurements obtained above and downwind of the leads. The basic observed features related to the lead‐generated convection can be reproduced with both closures, but the observed plume inclination and vertical entrainment near the inversion layer by the penetrating plume are underestimated. The advantage of the non‐local closure becomes obvious by the more realistic representation of regions with observed vertical entrainment or where the observations hint at counter‐gradient transport. It is shown by comparison with the observations that results obtained with the non‐local closure can be further improved by including the determination of a fetch‐dependent inversion height and by specifying a parameter determining the plume inclination as a function of the upwind ABL stratification. Both effects improve the representation of fluxes, boundary‐layer warming, and vertical entrainment. The model is also able to reproduce the observed vanishing of a weak low‐level jet over the lead, but its downwind regeneration and related momentum transport are not always well captured, irrespective of the closure used.
    Description: In typical springtime conditions of a cold atmospheric flow over the warm surfaces of leads, which are open‐water channels in sea ice, strong convective plumes are generated which have a large impact on atmospheric boundary‐layer characteristics. Here, a small‐scale model is applied to simulate such situations and model results obtained with different turbulence parametrizations are evaluated using airborne measurements. Based on the observations, a non‐local parametrization developed for the small‐scale modelling of the inhomogeneous convection over leads is further improved.
    Description: Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) via the Transregional Collaborative Research Center ArctiC Amplification (AC)3 (project number 268020496 TRR 172) and via the priority program SPP 1158 (grant LU 818/5‐1)
    Keywords: 551.5 ; aircraft observations ; atmospheric boundary layer ; convection over leads ; counter‐gradient transport ; entrainment ; microscale model ; sea ice ; turbulence parametrization
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    Arctic ocean–sea ice reanalysis for the period 2007–2016 using the adjoint method (2021)
    John Wiley & Sons, Ltd | Chichester, UK
    Details
    Publication Date: 2021-07-20
    Description: We present an Arctic ocean–sea ice reanalysis covering the period 2007–2016 based on the adjoint approach of the Estimating the Circulation and Climate of the Ocean (ECCO) consortium. The spatiotemporal variation of Arctic sea surface temperature (SST), sea ice concentration (SIC), and sea ice thickness (SIT) is substantially improved after the assimilation of ocean and sea ice observations. By assimilating additional World Ocean Atlas 2018 (WOA18) hydrographic data, the freshwater content of the Canadian Basin becomes closer to the observations and translates into changes of the ocean circulation and of transports through the Fram and Davis straits. This new reanalysis compares well with previous filter‐based (TOPAZ4) and nudging‐based (PIOMAS) reanalyses regarding SIC and SST. Benefiting from using the adjoint of the sea ice model, our reanalysis is superior to the ECCOv4r4 product considering sea ice parameters. However, the mean state and variability of the freshwater content and the transport properties of our reanalysis remain different from TOPAZ4 and ECCOv4r4, likely because of a lack of hydrographic observations.
    Description: Arctic sea ice has declined rapidly and reached a record minimum in September, 2012. Arctic ocean–sea ice reanalyses are invaluable sources for understanding the Arctic sea ice changes. We produce an Arctic ocean–sea ice reanalysis of the years 2007–2016 using the adjoint method. The reanalysis is dynamically consistent without introducing unphysical mass and energy discontinuities as in filter‐based data assimilation methods.
    Keywords: 551 ; adjoint method ; data assimilation ; ocean–sea ice reanalysis
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    Unusual appearance of mother‐of‐pearl clouds above El Calafate, Argentina (50°21′S, 72°16′W) (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-04-29
    Description: Visual observations from the ground and from a glider soaring in the lowermost stratosphere revealed the existence of stratospheric mother‐of‐pearl clouds above El Calafate in the lee of the Andes on 11 September 2019. The appearance of these clouds is rather unusual considering the time – end of the austral winter – and the location at about 50°S, being far away from Antarctica. This paper presents the available observations and describes the overall meteorological situation that was related to the earliest sudden stratospheric warming recorded so far in the Southern Hemisphere. By using high‐resolution numerical simulations, we show evidence of mountain waves propagating up to the stratosphere that are responsible for generating the localised cold stratospheric temperature anomalies required for ice cloud formation. Snapshots of a mother‐of‐pearl cloud from the camera installed at the PERLAN 2 aircraft's tail wing. image
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: 551.5 ; Argentina ; ice cloud formation
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    A new approach to classification of 40 years of Antarctic sea ice concentration data (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-07-04
    Description: In this paper, we present a characterization of Antarctic sea ice based on the classification of annual sea ice concentration (SIC) data from 1979 to 2018. A clustering algorithm was applied to provide a climatological description of significant annual cycles of SIC and their spatial distribution around the Southern Ocean. Based on these classification results, we investigate the variability of SIC cycles on decadal and inter‐annual time scales. First, we discuss significant spatial shifts of SIC cycles during 1979–1998 and 1999–2018. In the Weddell Sea and in large parts of the Ross Sea, we observed higher SIC during the summer season, and an extension of sea ice cover in winter compared to the long‐term average. Second, we introduce the Climatological Sea Ice Anomaly Index (CSIAI), which is an annual measure for year‐round sea ice anomalies of the Southern Ocean and its regional sub‐sectors. By relating selected years of significant sea ice conditions (1981, 2007 and 2014) with atmospheric influences, we demonstrate that the CSIAI is very useful for assessing inter‐annular Antarctic SIC variability. Positive and negative sea ice anomalies can be qualitatively explained by atmospheric circulation anomalies in the years 1981 and 2007. However, in 2014, the year with the largest observed sea ice extent in our time series, we found that this positive sea ice anomaly was surprisingly not associated with a stationary and inter‐seasonally persistent pattern of circulation anomaly. This suggests that sub‐seasonal to seasonal circulation anomalies and ocean‐related processes favoured the formation of the sea ice maximum in 2014. With this study we provide additional information on the long‐term annual SIC variability around Antarctica. Furthermore, our classification approach and its results have potential for application in the evaluation of sea ice model results.
    Description: In this paper, we present a characterization of Antarctic sea ice based on the classification of annual sea ice concentration cycles in the period 1979 to 2018. Furthermore, we discuss spatial shifts between 1979–1998 and 1999–2018 and are able to explain significant annual sea ice anomalies by atmospheric circulation anomalies.
    Description: DLR Management Board: Young Investigator Group Leader Program. F.R. was funded by the Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: 551.31 ; passive microwave data ; sea ice climatology ; sea ice trends ; sea ice variability
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    Severe thunderstorms with large hail across Germany in June 2019 (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-04-21
    Description: From 10 to 12 June 2019, severe thunderstorms affected large parts of Germany. Hail larger than golf ball size caused considerable damage, especially in the Munich area where losses amount to EUR 1 billion. This event thus ranks among the ten most expensive hail events in Europe in the last 40 years. Atmospheric blocking in combination with a moist, unstably stratified air mass provided an excellent setting for the development of severe, hail‐producing thunderstorms across the country. image
    Description: German Research Foundation http://dx.doi.org/10.13039/501100001659
    Keywords: 551.5 ; Germany ; thunderstorms ; hailstorm
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    Pre‐instrumental summer precipitation variability in northwestern Greece from a high‐elevation Pinus heldreichii network (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-07-04
    Description: The spatiotemporal variability of precipitation is of vital importance to Mediterranean ecology and economy, but pre‐instrumental changes are not well understood. Here, we present a millennial‐length June–July precipitation reconstruction derived from a network of 22 Pinus heldreichii high‐elevation sites in the Pindus Mountains of northwestern Greece. Tree‐ring width chronologies from these sites cohere exceptionally well over the past several hundred years (r1467–2015 = 0.64) revealing coherence at inter‐annual to centennial timescales across the network. The network mean calibrates significantly against instrumental June–July precipitation over the past 40 years (r1976–2015 = 0.71), even though no high‐elevation observational record is available representing the moist conditions at the treeline above 1,900 m a.s.l. For the final reconstruction, the instrumental target data are adjusted to provide realistic estimates of high‐elevation summer rainfall back to 729 CE. The reconstruction contains substantially more low‐frequency variability than other high‐resolution hydroclimate records from the eastern Mediterranean including extended dry periods from 1,350 to 1,379 CE (39 ± 4.5 mm) and 913 to 942 (40 ± 8.4 mm), and moist periods from 862 to 891 (86 ± 11 mm) and 1,522 to 1,551 (80 ± 3.5 mm), relative to the long‐term mean of 61 mm. The most recent 30‐year period from 1986 to 2015 is characterized by above average June–July precipitation (73 ± 2 mm). Low‐frequency changes in summer precipitation are likely related to variations in the position and persistence of storm tracks steering local depressions and causing extensive rainfall (or lack thereof) in high‐elevation environments of the Pindus Mountains.
    Description: Associated with a strengthening of circum‐global sub‐tropical high‐pressure belts, climate models unequivocally predict a decrease of Mediterranean precipitation, accompanied by an increase of extreme events in the upcoming decades. Long‐term desiccation will amplify evaporative demand challenging plant metabolism and foster an even greater need to irrigate Mediterranean crops. We place these recent hydroclimate dynamics into a long‐term context and explore the feasibility of reconstructing low‐frequency precipitation variability by employing a large network of high‐elevation Pinus heldreichii sites from northwestern Greece.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: 551.6 ; climate reconstruction ; Mediterranean ; Pindus Mountains ; pine ; tree‐rings ; Valia Calda
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    Grassland greening on the Mongolian Plateau despite higher grazing intensity (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-06-28
    Description: Changes in land management and climate alter vegetation dynamics, but the determinants of vegetation changes often remain elusive, especially in global drylands. Here we assess the determinants of grassland greenness on the Mongolian Plateau, one of the world's largest grassland biomes, which covers Mongolia and the province of Inner Mongolia in China. We use spatial panel regressions to quantify the impact of precipitation, temperature, radiation, and the intensity of livestock grazing on the normalized difference vegetation indices (NDVI) during the growing seasons from 1982 to 2015 at the county level. The results suggest that the Mongolian Plateau experienced vegetation greening from 1982 to 2015. Precipitation and animal density were the most influential factors contributing to higher NDVI on the grasslands of Inner Mongolia and Mongolia. Our results highlight the dominant effect of climate variability, and especially of the precipitation variability, on the grassland greenness in Mongolian drylands. The findings challenge the common belief that higher grazing pressure is the key driver for land degradation. The analysis exemplifies how representative wall‐to‐wall results for large areas can be attained from exploring space–time data and adds empirical insights to the puzzling relationship between grazing intensity and vegetation growth in dryland areas.
    Description: European Union's Framework Programme for Research and Innovation ‐ Horizon 2020 (2014‐2020)
    Description: Alexander von Humboldt Foundation of Germany
    Keywords: 333.7 ; China ; climate change ; grassland ; livestock grazing ; NDVI ; spatial panel regression ; vegetation growth
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    Contextualizing land‐use and land‐cover change with local knowledge: A case study from Pokot Central, Kenya (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-07-16
    Description: Rural communities in the drylands of sub‐Saharan Africa (SSA) derive their livelihoods primarily from their natural resource base. Unprecedented changes in these environments over the past few decades are likely to intensify in the future and land users need to develop sustainable adaptation strategies. This study aims to identify land‐use and land‐cover (LULC) changes and their drivers in a sub‐Saharan dryland, between 1986 and 2017, by integrating local knowledge and remote sensing. Local knowledge and environmental perception are used as the basis for defining LULC classes and for training and validation of change detection. This study detects significant LULC changes in 41% of the investigated area, and identifies bush encroachment into former pastures as the dominant LULC change with an increase of woodland by 39% and a decrease of grassland by 74%. This process is perceived as severe degradation by local respondents and is linked to changing management regimes and unreliable rainfall patterns. Deforestation and woodland thinning account for 44% of the detected changes, and can be traced back to increased habitation and farming, although the local community also identifies charcoal production as a driving factor. The integration of remote sensing and local knowledge provides a holistic view on LULC change in Pokot Central, Kenya and offers a solid base for site‐specific and actor‐centred management approaches necessary for sustainable pathways of drylands. Our results emphasize the need to include local actors in the development of adaptation strategies and management guidelines for drylands.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: Heidelberg University, Graduiertenförderung
    Keywords: 631.37 ; Kenya ; LANDSAT ; land‐use and land‐cover change ; local knowledge ; Pokot Central ; remote sensing
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    Comprehensive evaluation of an improved large‐scale multi‐site weather generator for Germany (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-06-29
    Description: In this work, we present a comprehensive evaluation of a stochastic multi‐site, multi‐variate weather generator at the scale of entire Germany and parts of the neighbouring countries covering the major German river basins Elbe, Upper Danube, Rhine, Weser and Ems with a total area of approximately 580,000 km2. The regional weather generator, which is based on a first‐order multi‐variate auto‐regressive model, is setup using 53‐year long daily observational data at 528 locations. The performance is evaluated by investigating the ability of the weather generator to replicate various important statistical properties of the observed variables including precipitation occurrence and dry/wet transition probabilities, mean daily and extreme precipitation, multi‐day precipitation sums, spatial correlation structure, areal precipitation, mean daily and extreme temperature and solar radiation. We explore two marginal distributions for daily precipitation amount: mixed Gamma‐Generalized Pareto and extended Generalized Pareto. Furthermore, we introduce a new procedure to estimate the spatial correlation matrix and model mean daily temperature and solar radiation. The extensive evaluation reveals that the weather generator is greatly capable of capturing most of the crucial properties of the weather variables, particularly of extreme precipitation at individual locations. Some deficiencies are detected in capturing spatial precipitation correlation structure that leads to an overestimation of areal precipitation extremes. Further improvement of the spatial correlation structure is envisaged for future research. The mixed marginal model found to outperform the extended Generalized Pareto in our case. The use of power transformation in combination with normal distribution significantly improves the performance for non‐precipitation variables. The weather generator can be used to generate synthetic event footprints for large‐scale trans‐basin flood risk assessment.
    Description: The regional weather generator is greatly capable of capturing most of the crucial statistical properties of weather events. Hence, it can be used to generate synthetic event footprints for large‐scale trans‐basin flood risk assessment. However, due to its deficiency in capturing spatial precipitation correlation structure leading to an overestimation of areal precipitation extremes, further improvement is envisaged for future research.
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: 551.6 ; correlation ; extreme ; flood ; large‐scale ; multi‐variate ; weather generator
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    The regional MiKlip decadal prediction system for Europe: Hindcast skill for extremes and user‐oriented variables (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-07-03
    Description: Regional climate predictions for the next decade are gaining importance, as this period falls within the planning horizon of politics, economy, and society. The potential predictability of climate indices or extremes at the regional scale is of particular interest. The German MiKlip project (“mid‐term climate forecast”) developed the first regional decadal prediction system for Europe at 0.44° resolution, based on the regional model COSMO‐CLM using global MPI‐ESM simulations as boundary conditions. We analyse the skill of this regional system focussing on extremes and user‐oriented variables. The considered quantities are related to temperature extremes, heavy precipitation, wind impacts, and the agronomy sector. Variables related to temperature (e.g., frost days, heat wave days) show high predictive skill (anomaly correlation up to 0.9) with very little dependence on lead‐time, and the skill patterns are spatially robust. The skill patterns for precipitation‐related variables (e.g., heavy precipitation days) and wind‐based indices (like storm days) are less skilful and more heterogeneous, particularly for the latter. Quantities related to the agronomy sector (e.g., growing degree days) show high predictive skill, comparable to temperature. Overall, we provide evidence that decadal predictive skill can be generally found at the regional scale also for extremes and user‐oriented variables, demonstrating how the utility of decadal predictions can be substantially enhanced. This is a very promising first step towards impact‐related modelling at the regional scale and the development of individual user‐oriented products for stakeholders.
    Description: The skill of the regional MiKlip decadal prediction system is analysed focussing on extremes and user‐oriented variables. Variables related to temperature extremes and the agronomy sector show high predictive skill with very little dependence on lead‐time. Skill patterns for precipitation‐related variables and wind‐based indices are less skilful and more heterogeneous, especially for the latter.
    Description: The study was mainly funded by the Bundesministerium für Bildung und Forschung (BMBF) under project FONA MiKlip‐II http://dx.doi.org/10.13039/501100002347
    Description: AXA Research Fund http://dx.doi.org/10.13039/501100001961
    Keywords: 551.6 ; climate services ; Europe ; extremes ; MiKlip ; regional decadal predictions ; user needs
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    Assessing land use and flood management impacts on ecosystem services in a river landscape (Upper Danube, Germany) (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-06-28
    Description: Rivers and floodplains provide many regulating, provisioning and cultural ecosystem services (ES) such as flood risk regulation, crop production or recreation. Intensive use of resources such as hydropower production, construction of detention basins and intensive agriculture substantially change ecosystems and may affect their capacity to provide ES. Legal frameworks such as the European Water Framework Directive, Bird and Habitats Directive and Floods Directive already address various uses and interests. However, management is still sectoral and often potential synergies or trade‐offs between sectors are not considered. The ES concept could support a joint and holistic evaluation of impacts and proactively suggest advantageous options. The river ecosystem service index (RESI) method evaluates the capacity of floodplains to provide ES by using a standardized five‐point scale for 1 km‐floodplain segments based on available spatial data. This scaling allows consistent scoring of all ES and their integration into a single index. The aim of this article is to assess ES impacts of different flood prevention scenarios on a 75 km section of the Danube river corridor in Germany. The RESI method was applied to evaluate scenario effects on 13 ES with the standardized five‐point scale. Synergies and trade‐offs were identified as well as ES bundles and dependencies on land use and connectivity. The ratio of actual and former floodplain has the strongest influence on the total ES provision: the higher the percentage and area of an active floodplain, the higher the sum of ES. The RESI method proved useful to support decision‐making in regional planning.
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Keywords: 333.91 ; assessment ; cultural ; floodplains ; index ; inter‐sectoral management ; regulating and provisioning ecosystem services ; stakeholders
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    Nonstationarity of the link between the Tropics and the summer East Atlantic pattern (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-07-03
    Description: A 700‐year pre‐industrial control run with the MPI‐ESM‐LR model is used to investigate the link between the summer East Atlantic (SEA) pattern and the Pacific‐Caribbean rainfall dipole (PCD), a link that has previously been shown using ERA‐Interim reanalysis data. In the model, it is found that the link between the SEA and PCD is present in some multidecadal epochs but not in others. A simple statistical model reproduces this behaviour. In the statistical model, the SEA is represented by a white noise process plus a weak influence from the PCD based on the full 700 years of the model run. The statistical model is relevant to other extratropical modes of variability, for example, the winter North Atlantic Oscillation (NAO), that are weakly influenced by the Tropics. It follows that the link between the Tropics and the winter NAO is likely to undergo modulation on multidecadal time scales, as found in some previous studies. The results suggest that any predictability of the SEA, and by implication the NAO, based on tropical rainfall may not be robust and may, in fact, be modulated on multidecadal time scales, with implications for seasonal and decadal prediction systems.
    Description: The positive phase of the SEA is associated with warm summers in Europe. The figure shows the running correlation in 51 year windows between the SEA index and the corresponding tropical rainfall index in a long pre‐industrial model run. The link between tropical rainfall and the SEA exists only in some decadal epochs, shown by the green shading, implying that predictability of the SEA based on tropical rainfall can be expected to vary on multidecadal time scales.
    Keywords: 551.5 ; nonstationarity ; seasonal prediction ; summer East Atlantic pattern
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    Convective rain cell characteristics and scaling in climate projections for Germany (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    Publication Date: 2021-07-03
    Description: Extreme convective precipitation is expected to increase with global warming. However, the rate of increase and the understanding of contributing processes remain highly uncertain. We investigated characteristics of convective rain cells like area, intensity, and lifetime as simulated by a convection‐permitting climate model in the area of Germany under historical (1976–2005) and future (end‐of‐century, RCP8.5 scenario) conditions. To this end, a tracking algorithm was applied to 5‐min precipitation output. While the number of convective cells is virtually similar under historical and future conditions, there are more intense and larger cells in the future. This yields an increase in hourly precipitation extremes, although mean precipitation decreases. The relative change in the frequency distributions of area, intensity, and precipitation sum per cell is highest for the most extreme percentiles, suggesting that extreme events intensify the most. Furthermore, we investigated the temperature and moisture scaling of cell characteristics. The temperature scaling drops off at high temperatures, with a shift in drop‐off towards higher temperatures in the future, allowing for higher peak values. In contrast, dew point temperature scaling shows consistent rates across the whole dew point range. Cell characteristics scale at varying rates, either below (mean intensity), at about (maximum intensity and area), or above (precipitation sum) the Clausius–Clapeyron rate. Thus, the widely investigated extreme precipitation scaling at fixed locations is a complex product of the scaling of different cell characteristics. The dew point scaling rates and absolute values of the scaling curves in historical and future conditions are closest for the highest percentiles. Therefore, near‐surface humidity provides a good predictor for the upper limit of for example, maximum intensity and total precipitation of individual convective cells. However, the frequency distribution of the number of cells depending on dew point temperature changes in the future, preventing statistical inference of extreme precipitation from near‐surface humidity.
    Description: We investigated characteristics of convective rain cells under historical and future conditions in convection‐permitting climate simulations using a tracking algorithm. There are more intense and larger cells in the future yielding an increase in hourly precipitation extremes. The temperature scaling curves of cell characteristics shift towards higher peak values at higher temperatures in the future. In contrast, cell characteristics scale consistently with dew point temperature. Therefore, near‐surface humidity provides a good predictor for the upper limit of for example, maximum intensity, and total precipitation of convective cells.
    Keywords: 551.6 ; Clausius–Clapeyron scaling ; convection‐permitting simulation ; convective storms ; COSMO‐CLM ; precipitation ; tracking
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    A high‐accuracy global prognostic model for the simulation of Rossby and gravity wave dynamics (2021)
    John Wiley & Sons, Ltd | Chichester, UK
    Details
    Publication Date: 2021-07-20
    Description: A model for studying Transient Inertia–Gravity And Rossby wave dynamics (TIGAR) is introduced. The presented horizontal component of the model solves the nonlinear rotating shallow‐water equations on the sphere using Hough harmonics. Spectral modelling using Hough harmonics as basis functions describes atmospheric dynamics in terms of physically identifiable structures: Rossby and inertia–gravity eigensolutions of linearized primitive equations. This offers an attractive framework for detangling gravity wave dynamics in high‐resolution simulations. Accurate computations are achieved through the use of higher order integrating factor and exponential time‐differencing methods, leading to a major increase in computational efficiency and stability. A comparison with classical time‐stepping schemes shows accuracy improvements of several orders of magnitude at no additional computational cost. In particular, stability gains are achieved through enhanced accuracy and efficiency in the computation of gravity waves, rather than through their damping. In the new framework, reduced models using Rossby and gravity waves aimed at studying dynamical aspects of data assimilation or wave interactions are easily implemented.
    Description: We present new global forecast model for Transient Inertia–Gravity And Rossby wave dynamics (TIGAR). By decomposing the flow into Rossby and gravity wave components and employing exponential time‐differencing schemes, TIGAR achieves remarkable gains in accuracy, efficiency, and stability. The figure compares forecast errors in Rossby and gravity waves computed by TIGAR with different time‐stepping algorithms in a barotropic instability test at T170 resolution.
    Description: UHH Ideen‐ und Risikofund
    Keywords: 551.52 ; exponential time‐stepping schemes ; gravity waves ; Hough harmonics ; nonlinear wave dynamics ; numerical model accuracy ; Rossby waves
    Type: article
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    Evolution of convective characteristics during tropical cyclogenesis (2021)
    John Wiley & Sons, Ltd | Chichester, UK
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    Publication Date: 2021-07-20
    Description: Four idealized, high‐resolution (500 m horizontal grid spacing), numerical simulations are used to investigate the evolution of convective structures during tropical cyclogenesis. The simulations all begin with a weak initial axisymmetric cloud‐free vortex in a quiescent environment, but differ in the moisture level of the initial sounding and whether or not ice microphysical processes are considered. Irrespective of experimental setup, there is only a short period where shallow or congestus clouds dominate. The shallow cloud phase is slightly extended with the drier initial environmental sounding. The composite structure of the convective elements sampled changes markedly throughout the genesis period. For much of the genesis phase, vertical profiles of the mean convective cell show significant amounts of anticyclonic vorticity produced in cells in the inner core. Towards the end of the genesis phase, there is a large increase in the production of cyclonic vertical vorticity in inner‐core convection, and cyclonic vorticity becomes dominant at low‐mid levels. The evolution from roughly equal strength vertical profiles of cyclonic/anticyclonic vorticity at low‐mid levels to profiles where cyclonic vorticity dominates occurs at relatively low system wind speeds (Vmax less than 10 m·s−1). This finding indicates a change in the structure of vortical convection prior to rapid intensification. In outer‐core convection, there are roughly equal strength vertical vorticity dipoles produced throughout the genesis period.
    Description: Four idealized, high‐resolution (500 m horizontal grid spacing), numerical simulations are used to investigate the evolution of convective structures during tropical cyclogenesis. The composite structure of the average convective element sampled changes markedly throughout the genesis period, and towards the end of the genesis phase there is a large increase in the production of cyclonic vertical vorticity in inner‐core convection, which becomes dominant at low‐mid levels. Irrespective of microphysical scheme and environmental sounding used, there is a short period where cumulus congestus clouds dominate, that is, when the mean cloud top is between 5 and 9 km height, a finding which is at odds with a prior theory claiming that tropical cyclogenesis can be viewed as a two‐stage process in which congestus clouds have a large dynamical and thermodynamical contribution at early stages.
    Description: German Research Council (Deutsche Forschungsgemeinschaft) http://dx.doi.org/10.13039/501100001659
    Keywords: 551.5 ; convection ; cyclogenesis ; hurricane ; tropical cyclone
    Type: article
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    Tillage erosion as an important driver of in‐field biomass patterns in an intensively used hummocky landscape (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
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    Publication Date: 2021-10-06
    Description: Tillage erosion causes substantial soil redistribution that can exceed water erosion especially in hummocky landscapes under highly mechanized large field agriculture. Consequently, truncated soil profiles can be found on hill shoulders and top slopes, whereas colluvial material is accumulated at footslopes, in depressions, and along downslope field borders. We tested the hypothesis that soil erosion substantially affects in‐field patterns of the enhanced vegetation index (EVI) of different crop types on landscape scale. The interrelation between the EVI (RAPIDEYE satellite data; 5 m spatial resolution) as a proxy for crop biomass and modeled total soil erosion (tillage and water erosion modeled using SPEROS‐C) was analyzed for the Quillow catchment (size: 196 km2) in Northeast Germany in a wet versus normal year for four crop types (winter wheat, maize, winter rapeseed, winter barley). Our findings clearly indicate that eroded areas had the lowest EVI values, while the highest EVI values were found in depositional areas. The differences in the EVI between erosional and depositional sites are more pronounced in the analyzed normal year. The net effect of total erosion on the EVI compared to areas without pronounced erosion or deposition ranged from −10.2% for maize in the normal year to +3.7% for winter barley in the wet year. Tillage erosion has been identified as an important driver of soil degradation affecting in‐field crop biomass patterns in a hummocky ground moraine landscape. While soil erosion estimates are to be made, more attention should be given toward tillage erosion.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: 631.4 ; agroscapelab Quillow ; crop biomass patterns ; EVI ; remote sensing ; tillage erosion
    Type: map
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