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  • 1
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    High-resolution global climate simulations with the ECMWF model in Project Athena: Experimental design, model climate and seasonal forecast skill (2012)
    AMER METEOROLOGICAL SOC
    In:  EPIC3Journal of Climate, AMER METEOROLOGICAL SOC, 25, pp. 3155-3172, ISSN: 0894-8755
    Details
    Publication Date: 2019-07-17
    Description: The sensitivity to the horizontal resolution of the climate, anthropogenic climate change, and seasonal predictive skill of the ECMWF model has been studied as part of Project Athena—an international collaboration formed to test the hypothesis that substantial progress in simulating and predicting climate can be achieved if mesoscale and subsynoptic atmospheric phenomena are more realistically represented in climate models. In this study the experiments carried out with the ECMWF model (atmosphere only) are described in detail. Here, the focus is on the tropics and the Northern Hemisphere extratropics during boreal winter. The resolutions considered in Project Athena for the ECMWF model are T159 (126 km), T511 (39 km), T1279 (16 km), and T2047 (10 km). It was found that increasing horizontal resolution improves the tropical precipitation, the tropical atmospheric circulation, the frequency of occurrence of Euro-Atlantic blocking, and the representation of extratropical cyclones in large parts of the Northern Hemisphere extratropics. All of these improvements come from the increase in resolution from T159 to T511 with relatively small changes for further resolution increases to T1279 and T2047, although it should be noted that results from this very highest resolution are from a previously untested model version. Problems in simulating the Madden–Julian oscillation remain unchanged for all resolutions tested. There is some evidence that increasing horizontal resolution to T1279 leads to moderate increases in seasonal forecast skill during boreal winter in the tropics and Northern Hemisphere extratropics. Sensitivity experiments are discussed, which helps to foster a better understanding of some of the resolution dependence found for the ECMWF model in Project Athena.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 2
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    Simulating the diurnal cycle of rainfall in global climate models: Resolution versus parameterization (2012)
    In:  EPIC3Clim. Dyn.1007/s00382-011-, e9, pp. 399-418
    Details
    Publication Date: 2019-07-17
    Description: The effects of horizontal resolution and the treatment of convection on simulation of the diurnal cycle of precipitation during boreal summer are analyzed in several innovative weather and climate model integrations. The simulations include: season-long integrations of the Non-hydrostatic Icosahedral Atmospheric Model (NICAM) with explicit clouds and convection; year-long integrations of the operational Integrated Forecast System (IFS) from the European Centre for Medium-range Weather Forecasts at three resolutions (125, 39 and 16 km); seasonal simulations of the same model at 10 km resolution; and seasonal simulations of the National Center for Atmospheric Research (NCAR) low-resolution climate model with and without an embedded two-dimensional cloud-resolving model in each grid box. NICAM with explicit convection simulates best the phase of the diurnal cycle, as well as many regional features such as rainfall triggered by advancing sea breezes or high topography. However, NICAM greatly overestimates mean rainfall and the magnitude of the diurnal cycle. Introduction of an embedded cloud model within the NCAR model significantly improves global statistics of the seasonal mean and diurnal cycle of rainfall, as well as many regional features. However, errors often remain larger than for the other higher-resolution models. Increasing resolution alone has little impact on the timing of daily rainfall in IFS with parameterized convection, yet the amplitude of the diurnal cycle does improve along with the representation of mean rainfall. Variations during the day in atmospheric prognostic fields appear quite similar among models, suggesting that the distinctive treatments of model physics account for the differences in representing the diurnal cycle of precipitation.
    Repository Name: EPIC Alfred Wegener Institut
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  • 3
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    Tropical cyclone climatology in a 10-km global atmospheric GCM: Toward weather-resolving climate modelling (2012)
    AMER METEOROLOGICAL SOC
    In:  EPIC3Journal of Climate, AMER METEOROLOGICAL SOC, 25(11), pp. 3867-3893, ISSN: 0894-8755
    Details
    Publication Date: 2019-07-17
    Description: Northern Hemisphere tropical cyclone (TC) activity is investigated in multiyear global climate simulations with the ECMWF Integrated Forecast System (IFS) at 10-km resolution forced by the observed records of sea surface temperature and sea ice. The results are compared to analogous simulations with the 16-, 39-, and 125-km versions of the model as well as observations. In the North Atlantic, mean TC frequency in the 10-km model is comparable to the observed frequency, whereas it is too low in the other versions. While spatial distributions of the genesis and track densities improve systematically with increasing resolution, the 10-km model displays qualitatively more realistic simulation of the track density in the western subtropical North Atlantic. In the North Pacific, the TC count tends to be too high in the west and too low in the east for all resolutions. These model errors appear to be associated with the errors in the large-scale environmental conditions that are fairly similar in this region for all model versions. The largest benefits of the 10-km simulation are the dramatically more accurate representation of the TC intensity distribution and the structure of the most intense storms. The model can generate a supertyphoon with a maximum surface wind speed of 68.4 m s−1. The life cycle of an intense TC comprises intensity fluctuations that occur in apparent connection with the variations of the eyewall/rainband structure. These findings suggest that a hydrostatic model with cumulus parameterization and of high enough resolution could be efficiently used to simulate the TC intensity response (and the associated structural changes) to future climate change.
    Repository Name: EPIC Alfred Wegener Institut
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  • 4
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    Revolutionizing climate modeling - Project Athena: A multi-institutional, international collaboration (2013)
    In:  EPIC3Bull. Amer. Meteor. Soc., 94(2), pp. 231-245
    Details
    Publication Date: 2019-07-17
    Description: Researchers began paving the way for efficient use of dedicated supercomputing facilities to enable higher resolution climate modeling with potentially large improvements in fidelity. The importance of using dedicated high-end computing resources to enable high spatial resolution in global climate models and advance knowledge of the climate system has been evaluated in an international collaboration called Project Athena. Inspired by the World Modeling Summit of 2008 and made possible by the availability of dedicated high-end computing resources provided by the National Science Foundation from October 2009 through March 2010, Project Athena demonstrated the sensitivity of climate simulations to spatial resolution and to the representation of subgrid-scale processes with horizontal resolutions up to 10 times higher than contemporary climate models. While many aspects of the mean climate were found to be reassuringly similar, beyond a suggested minimum resolution, the magnitudes and structure of regional effects can differ substantially. Project Athena served as a pilot project to demonstrate that an effective international collaboration can be formed to efficiently exploit dedicated supercomputing resources. The outcomes to date suggest that, in addition to substantial and dedicated computing resources, future climate modeling and prediction require a substantial research effort to efficiently explore the fidelity of climate models when explicitly resolving important atmospheric and oceanic processes.
    Repository Name: EPIC Alfred Wegener Institut
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  • 5
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    Regional Structure of the Indian Summer Monsoon in Observations, Reanalysis, and Simulation (2015)
    AMER METEOROLOGICAL SOC
    In:  EPIC3Journal of Climate, AMER METEOROLOGICAL SOC, 28, pp. 1824-1841, ISSN: 0894-8755
    Details
    Publication Date: 2019-07-17
    Description: Regional variations in seasonal mean Indian summer monsoon rainfall and circulation for the period 1979–2009 are investigated using multiple data products. The focus is on four separate regions: the Western Ghats (WG), the Ganges basin (GB), the Bay of Bengal (BB), and Bangladesh–northeastern India (BD). Data reliability varies strongly by region, with particularly low correlations between different products for the BB and BD regions. Correlations between regions are generally not statistically significant, indicating rainfall varies independently in these four regions. The diagnosed associations between rainfall, circulation, and sea surface temperatures can be sensitive to the choice of rainfall product, and multiple precipitation products may need to be analyzed in this region to ensure that the results are robust. Enhanced precipitation in the BD region is associated with anomalous anticyclonic circulation at 850 mb and westerly anomalies along the foothills of the Tibetan Plateau, while precipitation in the other regions is associated with cyclonic flow and easterlies. These associations provide a dynamical explanation for previously reported weak, negative correlations between BD and the other regions. In addition to observed products, atmosphere-only simulations made using the European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecast System (IFS) during Project Athena are analyzed. While the simulations do not reproduce the observed interannual variations in rainfall, the fidelity of the simulated precipitation and circulation structure is comparable to or even outperforms the different state-of-the-art reanalysis products considered. Accuracy in representing interannual variability and regional structure thus appears to be independent.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 6
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    New Calculation of Saturation Specific Humidity and Saturation Vapor Pressure in the COLA Atmospheric General Circulation Model (2005)
    Details
    Publication Date: 2021-05-19
    Description: A new method of computing the saturation specific humidity, qs, and saturation vapor pressure, es, is presented. This has been recently implemented in the Center for Ocean-Land- Atmosphere Studies (COLA) atmospheric general circulation model (AGCM). The new method offers high accuracy extending beyond the observed atmospheric temperature domain and yet is computationally competitive with most other methods used for this calculation. In addition a corresponding continuous function for the derivative of es with respect to temperature is also given. An inverse function to es is available as well. Included are small corrections to es to assure high accuracy. The design of the implementation permits the user to obtain whatever level of accuracy and detail might be desired. With this even detailed microphysical calculations with high computational efficiency can be done with small changes when the need arises.
    Description: Unpublished
    Keywords: Atmospheric circulation
    Repository Name: AquaDocs
    Type: Working Paper , Non-Refereed
    Format: 59383 bytes
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  • 7
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    New Astronomy in the COLA Atmospheric General Circulation Model (2005)
    Details
    Publication Date: 2021-05-19
    Description: Two new astronomy packages, Naval Observatory Vector Astrometry Subroutines/Jet Propulsion Laboratory (NOVAS/JPL) and Berger (1978), have been installed in the Center for Ocean-Land-Atmosphere Studies (COLA) atmospheric general circulation model (AGCM). These provide much greater accuracy and flexibility in representing the Sun’s position as seen by the Earth’s atmosphere in both realistic settings as well as those involving paleoclimate simulations and constrained astronomical parameter experiments. Their computational efficiency provide low cost for any period of time being simulated. Details and implementation are discussed. The errors are also reviewed and comparisons are made with the original Spencer (1971) astronomy calculation. The accuracy and speed these new codes obtain make them well suited for installation into any AGCM.
    Description: Center for Ocean-Land-Atmosphere Studies - Calverton
    Description: Published
    Keywords: Atmosphere-ocean system
    Repository Name: AquaDocs
    Type: Report , Non-Refereed
    Format: 60104 bytes
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  • 8
    Electronic Resource
    Electronic Resource
    Lipæmia and Calcæmia in the Cock induced by Diethylstilbœstrol (1939)
    [s.l.] : Nature Publishing Group
    Nature 143 (1939), S. 378-379 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] RATS as well as chickens are transformed into eunuchoid dwarfs by prolonged treatment with cestrogenic hormone1. During these experiments, a high degree of lipsemia was found in the chickens2. The total blood fat can rise to 8,000 mgm. per cent (the normal being ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/143378a0
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  • 9
    Electronic Resource
    Electronic Resource
    Developing a national science culture under free trade - What kind of knowledge do we need?
    Amsterdam : Elsevier
    Technology in Society 11 (1989), S. 203-211 
    Details
    ISSN: 0160-791X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Sociology , Technology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0160-791X(89)90014-6
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  • 10
    Electronic Resource
    Electronic Resource
    Zur Thermodynamischen Begründung der Kovats'schen Retentionsindizes (1971)
    Springer
    Chromatographia 4 (1971), S. 459-462 
    Details
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Ausgehend von den thermodynamischen Grundlagen wird die Siedepunktsabhängigkeit der Retentionszeiten diskutiert. Über eine Formel vonKlages, nach der sich das Quadrat der Siedetemperaturen organischer Stoffe als additive Moleküleigenschaft darstellt, lassen sich die Retentionszeiten in eine analytische Beziehung zur Kohlenstoffzahl setzen. Nach Linearisierung dieser Beziehung läßt sich das System derKovats'schen Indizes zwanglos einführen. Der Anwendungsbereich desKovats'schen Systems sowie einer Formel für die Totzeit kann auf diese Weise abgegrenzt werden.
    Abstract: Résumé Partant des principes de la thermodynamique, on étudie la relation existant entre les temps de rétention et les points d'ébullition. Au moyen d'une formule deKlages, dans laquelle le carré des températures d'ébullition des substances organiques est présenté comme une caractéristique supplémentaire des molécules, on peut établir une realtion analytique entre le temps de rétention et le nombre d'atomes de carbone. Après linéarisation de cette relation, le système des indices deKovats peut être introduit facilement. De cette façon on peut délimiter la zone d'application du système deKovats, et déterminer une formule de calcul du temps mort.
    Notes: Summary Based on basic thermodynamics, the dependence of the retention times on the boiling points is discussed. Using an equation derived byKlages, in which the square of the boiling temperatures of organic substances is presented as an additive quality of the molecules an analytical relationship may be established between the retention time and the carbon number. After linearization of this relation, theKovats index system can be introduced without any problem. In this way, the application range of theKovats system and of an equation for the gas holdup time can be determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02268815
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