ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Other Sources  (34)
  • Chichester, UK  (27)
  • Wiley
  • 2020-2022  (34)
  • 1
    facet.materialart.
    Unknown
    Cyclic thermal fluctuations can be burden or relief for an ectotherm depending on fluctuations’ average and amplitude (2021)
    British Ecological Society | Wiley
    In:  Functional Ecology, 35 (11). pp. 2483-2496.
    Details
    Publication Date: 2021-11-10
    Description: Predicting the implications of ongoing ocean climate warming demands a better understanding of how short-term thermal variability impacts marine ectotherms, particularly at beyond-optimal average conditions during summer heatwaves. Using a globally important model species, the blue mussel Mytilus, in a 5-week-long experiment, we (a) assessed growth performance traits under 12 scenarios, consisting of four thermal averages (18.5, 21, 23.5 and 26℃) imposed as constant or daily fluctuating regimes with amplitudes of 2 or 4℃. Additionally, we conducted a short-term assay using different mussel individuals to (b) test for the species capacity for suppression and recovery of metabolic performance traits (feeding and aerobic respiration) when exposed to a 1-day thermal fluctuation regime (16.8–30.5℃). Using this high-resolution data, we (c) generated short-term thermal metabolic performance curves to predict and explain growth responses observed in the long-term experiment. We found that daily high-amplitude thermal cycles (4℃) improved mussel growth when fluctuations were imposed around an extreme average temperature of 26℃, representing end-of-century heatwaves. In contrast, thermal cycles negatively affected mussel growth at a less extreme average temperature of 23.5℃, resembling current peak summer temperature scenarios. These results suggest that fluctuations ameliorate heat stress impacts only at critically high average temperatures. The short-term assay demonstrated that during the warming phase, animals stopped feeding between 24 and 30℃ while gradually suppressing respiration. In the subsequent cooling phase, feeding and respiration partially and fully recovered to pre-heating rates respectively. Furthermore, nonlinear averaging of short-term feeding responses (upscaling) well-predicted longer term growth responses to fluctuations. Our findings suggest that fluctuations can be beneficial to or detrimental for the long-term performance of ectothermic animals, depending on the fluctuations' average and amplitude. Furthermore, the observed effects can be linked to fluctuation-mediated metabolic suppression and recovery. In a general framework, we propose various hypothetical scenarios of fluctuation impacts on ectotherm performance considering inter- or intra-species variability in heat sensitivity. Our research highlights the need for studying metabolic performance in relation to cyclic abiotic fluctuations to advance the understanding of climate change impacts on aquatic systems. A free Plain Language Summary can be found within the Supporting Information of this article
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER (OCEANREP)
  • 2
    facet.materialart.
    Unknown
    Tillage erosion as an important driver of in‐field biomass patterns in an intensively used hummocky landscape (2021)
    John Wiley & Sons, Ltd. | Chichester, UK
    Details
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 3
    facet.materialart.
    Unknown
    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
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 4
    facet.materialart.
    Unknown
    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
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 5
    facet.materialart.
    Unknown
    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
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 6
    facet.materialart.
    Unknown
    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
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 7
    facet.materialart.
    Unknown
    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.
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 8
    facet.materialart.
    Unknown
    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
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 9
    facet.materialart.
    Unknown
    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
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
  • 10
    facet.materialart.
    Unknown
    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
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    CITATION GEO-LEO
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...