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  • 【期刊】 Historical and future anthropogenic emission pathways derived from coupled climate–carbon cycle simulations

    刊名:Climatic Change 作者:Erich Roeckner ; M. A. Giorgetta ; T. Crueger ; M. Esch ; Julia Pongratz 年份:2011
    摘要:Using a coupled climate-carbon cycle model, fossil fuel carbon dioxide (CO2) emissions are derived through a reverse approach of prescribing atmospheric CO2 concentrations according to observations and future projections, respectively. In the second half of the twentieth century, the implied fossil fuel emissions, and also the carbon uptake by land and ocean, are within the range of observational estimates. Larger discrepancies exist in the earlier period (1860-1960), with small fossil fuel emissions and uncertain emissions from anthropogenic land cover change. In the IPCC SRES A1B scenario, the simulated fossil fuel emissions more than double until 2050 (17 GtC/year) and then decrease to 12 GtC/year by 2100. In addition to A1B, an aggressive mitigation scenario was employed, developed within the European ENSEMBLES project, that peaks at 530 ppm CO2(equiv) around 2050 and then decreases to approach 450 ppm during the twenty-second century. Consistent with the prescribed pathway of atmospheric CO2 in E1, the implied fossil fuel emissions increase from currently 8 GtC/year to about 10 by 2015 and decrease thereafter. In the 2050s (2090s) the emissions decrease to 3.4 (0.5) GtC/year, respectively. As in previous studies, our model simulates a positive climate-carbon cycle feedback which tends to reduce the implied emissions by roughly 1 GtC/year per degree global warming. Further, our results suggest that the 450 ppm stabilization scenario may not be sufficient to fulfill the European Union climate policy goal of limiting the global temperature increase to a maximum of 2A degrees C compared to pre-industrial levels.
  • 【期刊】 Impact of melt ponds on Arctic sea ice in past and future climates as simulated by MPI-ESM

    刊名:Journal of Advances in Modeling Earth Systems 作者:Erich Roeckner ; Thorsten Mauritsen ; Monika Esch and Renate Brokopf 年份:2012
  • 【期刊】 Climate and carbon cycle changes from 1850 to 2100 in MPI-ESM simulations for the Coupled Model Intercomparison Project phase 5

    摘要:[1] The new Max-Planck-Institute Earth System Model (MPI-ESM) is used in the Coupled Model Intercomparison Project phase 5 (CMIP5) in a series of climate change experiments for either idealized CO2-only forcing or forcings based on observations and the Representative Concentration Pathway (RCP) scenarios. The paper gives an overview of the model configurations, experiments related forcings, and initialization procedures and presents results for the simulated changes in climate and carbon cycle. It is found that the climate feedback depends on the global warming and possibly the forcing history. The global warming from climatological 1850 conditions to 2080–2100 ranges from 1.5°C under the RCP2.6 scenario to 4.4°C under the RCP8.5 scenario. Over this range, the patterns of temperature and precipitation change are nearly independent of the global warming. The model shows a tendency to reduce the ocean heat uptake efficiency toward a warmer climate, and hence acceleration in warming in the later years. The precipitation sensitivity can be as high as 2.5% K−1 if the CO2 concentration is constant, or as small as 1.6% K−1, if the CO2 concentration is increasing. The oceanic uptake of anthropogenic carbon increases over time in all scenarios, being smallest in the experiment forced by RCP2.6 and largest in that for RCP8.5. The land also serves as a net carbon sink in all scenarios, predominantly in boreal regions. The strong tropical carbon sources found in the RCP2.6 and RCP8.5 experiments are almost absent in the RCP4.5 experiment, which can be explained by reforestation in the RCP4.5 scenario.
  • 【期刊】 具有简单云模式的郭晓岚积雨云参数化格式的预诊和半预诊数值试验

    刊名:高原气象 作者:张志明 ; Erich Roeckner 机构:成都科技大学水利系 ; 成都科技大学水利系 ; 汉堡大学气象系 年份:1983
    摘要:本文给出了一个用于大气坏流模式中的积雨云参数化方法。该参数化格式的基本出友点与郭晓岚(1974)方法相同,即认为在由于大尺度水汽平流辐合及下垫面的水汽蒸发而具备充足的水汽供给的条件下。在条件性不稳定大气中可以发展出积雨云。 积雨云参数,如温度、水含量、垂直速度和吸入等都由一个一维云模式给出。 本格式用于Thompson等根据GATE实验第三阶段大西洋东部热带的观测资料合成的东风波的个例研究。文中就降水率和对流云作为感热源及潜热汇的作用等方面,比校了格式所得的结果与Thompson等由大尺度观测分析计算得出的事实。 最后,将该格式嵌入以实际观测值为初始条件的半球大气环流模式中,进行了模拟时间为48小时的数值试验,并与嵌入郭晓岚(1965)格式所得的结果进行了比较。
  • 【会议】 Comparison of Cloud Fields from AGCM, In Situ and Satellite Measurements

    摘要:Abstract This paper focuses on the comparison of cloud amounts derived from an Atmospheric General Circulation Model (AGCM); Satellite-observed clouds; and Groundbased cloud observations. This is distinctly different from Earth Radiation Budget Experiment (ERBE)-type comparisons because it does not mix potential errors in the cloud amount with those in the radiation code embedded in the model. Long term cloud climatologies were used to compare global cloud amounts and regional seasonal cycles. The results obtained were surprising in many respects. The AGCM successfully reproduced the signatures of the warm pool and North Pacific seasonal cycle cloudiness but failed in the low stratus region off the coast of South America; a known problem for AGChls. The data sets also reproduced the anomaly signature associated with El Nifio in the warm pool region; but the model amounts were lower. Global results had a similar success rate; with the model generally producing lower total cloud amounts compared to the satellite and in situ measurements. Also; an attempt was made to compare cloud vertical distributions between the data sets. Because of the inherent differences in the measuring processes among the three data sets; the cloud height may need to be validated using the corresponding radiation fields. Unfortunately there were also some large discrepancies between the two observed cloud data sets. We conclude that the character of the observed cloud data sets; while tremendously improveci over the last decade; must be substantially enhanced before they will be useful in validating AGCMS by any but the crudest levels of comparison.
  • 【会议】 Simulation of the hydrological cycle over Europe: Model validation and impacts of increasing greenhouse gases

    作者:Klaus Arpe ; Erich Roeckner 年份:未知
    摘要:Di€erent methods of estimating precipitation area means; based on observations; are compared with each other to investigate their usefulness for model validation. For the applications relevant to this study the ECMWF reanalyses provide a good and comprehensive data set for validation. The uncertainties of precipitation analyses; based on observed precipitation or from numerical weather forecasting schemes; are generally in the range of 20% but regionally much larger. The MPI atmospheric general circulation model is able to reproduce long term means of the main features of the hydrological cycle within the range of uncertainty of observational data; even for relatively small areas such as the Rhine river basin. Simulations with the MPI coupled general circulation model; assuming a further increase of anthropogenic greenhouse gases; show clear trends in temperature and precipitation for the next century which would have signi®cant implications for human activity; e.g. a further increase of the sea level of the Caspian Sea and less water in the Rhine and the Danube. We have gained con®dence in these results because trends in the temperature and precipitation in the coupled model simulations up to the present are partly con®rmed by an atmospheric model simulation forced with observed SSTs and by observational data. We gained further con®dence because the simulations with the same coupled model but using constant greenhouse gases do not show such trends. However; doubts arise from the fact that these trends are strong where the systematic errors of the model are large. Ó 1999 Elsevier Science Ltd. All rights reserved.
  • 【会议】 Tropical Intraseasonal Variability in 14 IPCC AR4 Climate Models. Part I: Convective Signals

    摘要:This study evaluates the tropical intraseasonal variability; especially the fidelity of Madden–Julian oscillation (MJO) simulations; in 14 coupled general circulation models (GCMs) participating in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). Eight years of daily precipitation from each model’s twentieth-century climate simulation are analyzed and compared with daily satellite-retrieved precipitation. Space–time spectral analysis is used to obtain the variance and phase speed of dominant convectively coupled equatorial waves; including the MJO; Kelvin; equatorial Rossby (ER); mixed Rossby–gravity (MRG); and eastward inertio–gravity (EIG) and westward inertio–gravity (WIG) waves. The variance and propagation of the MJO; defined as the eastward wavenumbers 1–6; 30–70-day mode; are examined in detail. The results show that current state-of-the-art GCMs still have significant problems and display a wide range of skill in simulating the tropical intraseasonal variability. The total intraseasonal (2–128 day) variance of precipitation is too weak in most of the models. About half of the models have signals of convectively coupled equatorial waves; with Kelvin and MRG–EIG waves especially prominent. However; the variances are generally too weak for all wave modes except the EIG wave; and the phase speeds are generally too fast; being scaled to excessively deep equivalent depths. An interesting result is that this scaling is consistent within a given model across modes; in that both the symmetric and antisymmetric modes scale similarly to a certain equivalent depth. Excessively deep equivalent depths suggest that these models may not have a large enough reduction in their “effective static stability” by diabatic heating. The MJO variance approaches the observed value in only 2 of the 14 models; but is less than half of the observed value in the other 12 models. The ratio between the eastward MJO variance and the variance of its westward counterpart is too small in most of the models; which is consistent with the lack of highly coherent eastward propagation of the MJO in many models. Moreover; the MJO variance in 13 of the 14 models does not come from a pronounced spectral peak; but usually comes from part of an overreddened spectrum; which in turn is associated with too strong persistence of equatorial precipitation. The two models that arguably do best at simulating the MJO are the only ones having convective closures/triggers linked in some way to moisture convergence. Corresponding author address: Dr. Jia-Lin Lin; NOAA–CIRES Climate Diagnostics Center; 325 Broadway; R/CDC1; Boulder; CO 80305-3328. E-mail: jialin.lin@noaa.gov 15 JUNE 2006 L I N E T A L . 2665 © 2006 American Meteorological Society
  • 【会议】 The Atmospheric General Circulation Model Echam-4: Model Description and Simulation of Present-day Climate

    作者:Erich Roeckner ; K. Arpe 年份:未知
    摘要:A detailed description of the fourth-generation ECHAM model is presented. Compared to the previous version; ECHAM-3; a number of substantial changes have been introduced in both the numerics and physics of the model. These include a semi-Lagrangian transport scheme for water vapour; cloud water and trace substances; a new radiation scheme (ECMWF) with modifications concerning the water vapour continuum; cloud optical properties and greenhouse gases; a new formulation of the vertical diffusion coefficients as functions of turbulent kinetic energy; and a new closure for deep convection based on convective instability instead of moisture convergence. Minor changes concern the parameterizations of horizontal diffusion; stratiform clouds and land surface processes. Also; a new dataset of land surface parameters have been compiled for the new model. The climatology of the model; derived from two extended AMIP simulations at T42L19 resolution; is documented and compared with ECMWF operational analyses. Some of the biases noted for the previous model version remain virtually unchanged. For example; the polar upper troposphere and lower stratosphere is much too cold; and the zonal wind errors become very large above the 200 hPa level. Furthermore; the low-frequency variability is still too small but the errors are reduced by about 50% compared to ECHAM-3. The tropospheric temperature and zonal wind errors are generally smaller than in the previous model; except for the tropics; where the overestimation of Walker-type circulations in the equatorial plane is even more pronounced in the new model and the simulation of the Indian summer monsoon is less realistic. The most substantial improvements; compared to ECHAM-3; are found for the land surface climate. The temperature and precipitation errors are generally smaller than before; and the biome distributions derived from these parameters are more realistic in ECHAM-4. These improvements can be attributed to an improved represention of surface radiation fluxes via larger absorption of solar radiation in the atmosphere due to both water vapour and clouds.
  • 【会议】 The evolution of the global aerosol system in a transient climate simulation from 1860 to 2100

    作者:Philip Stier ; Johann Feichter ; Erich Roeckner ; S Kloster ; Monika Esch 关键词:Sulfate ; Emission ; Aerosol ; DMS ; SION 年份:未知
    摘要:The evolution of the global aerosol system from 1860 to 2100 is investigated through a transient atmosphereocean General Circulation Model climate simulation with interactively coupled atmospheric aerosol and oceanic biogeochemistry modules. The microphysical aerosol module HAM incorporates the major global aerosol cycles with prognostic treatment of their composition; size distribution; and mixing state. Based on an SRES A1B emission scenario; the global mean sulfate burden is projected to peak in 2020 while black carbon and particulate organic matter show a lagged peak around 2070. From present day to future conditions the anthropogenic aerosol burden shifts generally from the northern high-latitudes to the developing low-latitude source regions with impacts on regional climate. Atmospheric residenceand aging-times show significant alterations under varying climatic and pollution conditions. Concurrently; the aerosol mixing state changes with an increasing aerosol mass fraction residing in the internally mixed accumulation mode. The associated increase in black carbon causes a more than threefold increase of its co-single scattering albedo from 1860 to 2100. Mid-visible aerosol optical depth increases from pre-industrial times; predominantly from the aerosol fine fraction; peaks at 0.26 around the sulfate peak in 2020 and maintains a high level thereafter; due to the continuing increase in carbonaceous aerosols. The global mean anthropogenic top of the atmosphere clear-sky short-wave direct aerosol radiative perturbation intensifies to −1.1 W m−2 around 2020 and weakens after 2050 to −0.6 W m−2; owing to an increase in atmospheric absorption. The demonstrated modifications in the aerosol residenceand aging-times; the microphysical state; and radiative properties challenge simplistic approaches to estimate the aerosol radiative effects from emission projections. Correspondence to: P. Stier (philip.stier@caltech.edu)
  • 【会议】 Forcing of the quasi-biennial oscillation from a broad spectrum of atmospheric waves

    作者:Marco Giorgetta ; Elisa Manzini ; Erich Roeckner 年份:未知
    摘要:[1] The circulation of the stratosphere; and its influence on the trace constituent distribution; is an important component of the climate system; which must be included in simulations of global climate change. However; the ability to simulate a dominant stratospheric phenomenon; the Quasi-Biennial Oscillation (QBO) in equatorial zonal wind; is an outstanding challenge in climate modeling. Although confined to the tropics; the QBO affects the circulation and the interannual variability of the entire stratosphere; parts of the mesosphere and possibly also of the troposphere. Here we show that the QBO is successfully simulated in a general circulation model (GCM) of the newest generation. Key factors are a sufficient spatial resolution; a realistic simulation of tropical convection; and the consideration of the effects of gravity waves. From this simulation it is inferred that a broad spectrum of atmospheric waves is necessary to generate the QBO in the model.
  • 【会议】 Global mean cloud feedbacks in idealized climate change experiments

    摘要:[1] Global mean cloud feedbacks in ten atmosphere-only climate models are estimated in perturbed sea surface temperature (SST) experiments and the results compared to doubled CO2 experiments using mixed-layer ocean versions of these same models. The cloud feedbacks in any given model are generally not consistent: the sign of the net cloud radiative feedback may vary according to the experimental design. However; both sets of experiments indicate that the variation of the total climate feedback across the models depends primarily on the variation of the net cloud feedback. Changes in different cloud types show much greater consistency between the two experiments for any individual model and amongst the set of models analyzed here. This suggests that the SST perturbation experiments may provide useful information on the processes associated with cloud changes which is not evident when analysis is restricted to feedbacks defined in terms of the change in cloud radiative forcing. Citation: Ringer; M. A.; et al. (2006); Global mean cloud feedbacks in idealized climate change experiments; Geophys. Res. Lett.; 33; L07718; doi:10.1029/ 2005GL025370.
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