scholarly journals Incorporation of inline warm rain diagnostics into the COSP2 satellite simulator for process-oriented model evaluation

2019 ◽  
Vol 12 (10) ◽  
pp. 4297-4307 ◽  
Author(s):  
Takuro Michibata ◽  
Kentaroh Suzuki ◽  
Tomoo Ogura ◽  
Xianwen Jing
Keyword(s):  
Optical Depth ◽  
General Circulation ◽  
Regional Analysis ◽  
Circulation Model ◽  
Radar Reflectivity ◽  
Multiple Model ◽  
Climatic Impact ◽  
Warm Rain ◽  
Process Oriented ◽  
Warm Rain Process

Abstract. The Cloud Feedback Model Intercomparison Project Observational Simulator Package (COSP) is used to diagnose model performance and physical processes via an apple-to-apple comparison to satellite measurements. Although the COSP provides useful information about clouds and their climatic impact, outputs that have a subcolumn dimension require large amounts of data. This can cause a bottleneck when conducting sets of sensitivity experiments or multiple model intercomparisons. Here, we incorporate two diagnostics for warm rain microphysical processes into the latest version of the simulator (COSP2). The first one is the occurrence frequency of warm rain regimes (i.e., non-precipitating, drizzling, and precipitating) classified according to CloudSat radar reflectivity, putting the warm rain process diagnostics into the context of the geographical distributions of precipitation. The second diagnostic is the probability density function of radar reflectivity profiles normalized by the in-cloud optical depth, the so-called contoured frequency by optical depth diagram (CFODD), which illustrates how the warm rain processes occur in the vertical dimension using statistics constructed from CloudSat and MODIS simulators. The new diagnostics are designed to produce statistics online along with subcolumn information during the COSP execution, eliminating the need to output subcolumn variables. Users can also readily conduct regional analysis tailored to their particular research interest (e.g., land–ocean differences) using an auxiliary post-process package after the COSP calculation. The inline diagnostics are applied to the MIROC6 general circulation model (GCM) to demonstrate how known biases common among multiple GCMs relative to satellite observations are revealed. The inline multi-sensor diagnostics are intended to serve as a tool that facilitates process-oriented model evaluations in a manner that reduces the burden on modelers for their diagnostics effort.

scholarly journals Incorporation of inline warm-rain diagnostics into the COSP2 satellite simulator for process-oriented model evaluation

2019 ◽  
Author(s):  
Takuro Michibata ◽  
Kentaroh Suzuki ◽  
Tomoo Ogura ◽  
Xianwen Jing
Keyword(s):  
Regional Analysis ◽  
Model Performance ◽  
Multiple Model ◽  
Climatic Impact ◽  
Process Diagnostics ◽  
Post Process ◽  
Warm Rain ◽  
Process Oriented ◽  
Warm Rain Process ◽  
Microphysical Processes

Abstract. Cloud Feedback Model Intercomparison Project Observational Simulator Package (COSP) has been widely used to diagnose model performance and physical processes via an apple-to-apple comparison to satellite measurements. Although the COSP provides useful information about clouds and their climatic impact, outputs that have a subcolumn dimension require large amounts of data. This can cause a bottleneck when conducting sets of sensitivity experiments or multiple model intercomparisons. Here, we incorporate two diagnostics for warm-rain microphysical processes into COSP2, the latest version of the simulator. The approach used here employs existing diagnostic methodologies that probe how the warm-rain processes occur using statistics constructed from simulators of multiple satellite instruments along with their subcolumn information. The new diagnostics are designed to produce statistics online during the COSP execution, eliminating the need to output subcolumn variables. Users can also readily conduct regional analysis tailored to their particular research interest (e.g., land–ocean differences), using an auxiliary post-process package after the COSP calculation. This inline tool also generates global maps of the occurrence frequency of warm-rain regimes (i.e., non-precipitating, drizzling, and precipitating) classified according to CloudSat radar reflectivity, putting the warm-rain process diagnostics into the context of geographical distributions of precipitation. The inline diagnostics are applied to the MIROC6 GCM to demonstrate how known biases common among multiple GCMs relative to satellite observations are revealed. The inline multisensor diagnostics are intended to serve as a tool that facilitates process-oriented model evaluations in a manner that reduces the burden on modelers for their diagnostics effort.

scholarly journals Stratospheric aerosol radiative forcing simulated by the chemistry climate model EMAC using aerosol CCI satellite data

2018 ◽  
Author(s):  
Christoph Brühl ◽  
Jennifer Schallock ◽  
Klaus Klingmüller ◽  
Charles Robert ◽  
Christine Bingen ◽  
...  
Keyword(s):  
Optical Depth ◽  
Radiative Forcing ◽  
General Circulation ◽  
Asian Summer Monsoon ◽  
Michelson Interferometer ◽  
Circulation Model ◽  
Volcanic Eruptions ◽  
Radiative Heating ◽  
Tropospheric Aerosol ◽  
Atmospheric Sounding

Abstract. This paper presents decadal simulations of stratospheric and tropospheric aerosol by the chemistry general circulation model EMAC constrained with satellite observations in the framework of the ESA-Aerosol-CCI project like GOMOS (Global Ozone Monitoring by Occultation of Stars) and (A)ATSR ((Advanced) Along Track Scanning Radiometer) on ENVISAT (European Environmental Satellite), and IASI (Infrared Atmospheric Sounding Interferometer) on Metop (Meteorological Operational Satellite). The EMAC simulations with modal interactive aerosol and observations by GOMOS show that sulfate particles from about 230 volcanic eruptions identified mostly from MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) SO2 limb measurements dominate the interannual variability of aerosol extinction in the lower stratosphere, and of radiative forcing at the tropopause. To explain the observations, desert dust and organic and black carbon, transported to the lowermost stratosphere by the Asian summer monsoon and tropical convection, are also important. This holds also for radiative heating by aerosol in the lowermost stratosphere. Comparison with (A)ATSR total aerosol optical depth at different wavelengths and IASI dust optical depth shows that the model is able to represent stratospheric and tropospheric aerosol in a consistent way.

The Influence of Meridional Gradients in Insolation and Longwave Optical Depth on the Climate of a Gray Radiation GCM

2018 ◽  
Vol 31 (19) ◽  
pp. 7803-7822
Author(s):  
Nicholas J. Lutsko ◽  
Max Popp
Keyword(s):  
Surface Temperature ◽  
Optical Depth ◽  
General Circulation ◽  
Prognostic Model ◽  
Circulation Model ◽  
Lapse Rate ◽  
The Earth ◽  
Global Mean Surface Temperature ◽  
Earth’S Climate ◽  
Global Mean

The relative contributions of the meridional gradients in insolation and in longwave optical depth (caused by gradients in water vapor) to the equator-to-pole temperature difference, and to Earth’s climate in general, have not been quantified before. As a first step to understanding these contributions, this study investigates simulations with an idealized general circulation model in which the gradients are eliminated individually or jointly, while keeping the global means fixed. The insolation gradient has a larger influence on the model’s climate than the gradient in optical depth, but both make sizeable contributions and the changes are largest when the gradients are reduced simultaneously. Removing either gradient increases global-mean surface temperature due to an increase in the tropospheric lapse rate, while the meridional surface temperature gradients are reduced. “Global warming” experiments with these configurations suggest similar climate sensitivities; however, the warming patterns and feedbacks are quite different. Changes in the meridional energy fluxes lead to polar amplification of the response in all but the setup in which both gradients are removed. The lapse-rate feedback acts to polar amplify the responses in the Earth-like setup, but is uniformly negative in the other setups. Simple models are used to interpret the results, including a prognostic model that can accurately predict regional surface temperatures, given the meridional distributions of insolation and longwave optical depths.

scholarly journals Effects of Cloud Microphysics on Tropical Atmospheric Hydrologic Processes and Intraseasonal Variability

2005 ◽  
Vol 18 (22) ◽  
pp. 4731-4751 ◽  
Author(s):  
K. M. Lau ◽  
H. T. Wu ◽  
Y. C. Sud ◽  
G. K. Walker
Keyword(s):  
General Circulation ◽  
Large Scale ◽  
Water Cycle ◽  
Deep Convection ◽  
Intraseasonal Variability ◽  
Lower Troposphere ◽  
Circulation Model ◽  
Cloud Microphysics ◽  
Hydrologic Processes ◽  
Warm Rain

Abstract The sensitivity of tropical atmospheric hydrologic processes to cloud microphysics is investigated using the NASA Goddard Earth Observing System (GEOS) general circulation model (GCM). Results show that a faster autoconversion rate leads to (a) enhanced deep convection in the climatological convective zones anchored to tropical land regions; (b) more warm rain, but less cloud over oceanic regions; and (c) an increased convective-to-stratiform rain ratio over the entire Tropics. Fewer clouds enhance longwave cooling and reduce shortwave heating in the upper troposphere, while more warm rain produces more condensation heating in the lower troposphere. This vertical differential heating destabilizes the tropical atmosphere, producing a positive feedback resulting in more rain and an enhanced atmospheric water cycle over the Tropics. The feedback is maintained via secondary circulations between convective tower and anvil regions (cold rain), and adjacent middle-to-low cloud (warm rain) regions. The lower cell is capped by horizontal divergence and maximum cloud detrainment near the freezing–melting (0°C) level, with rising motion (relative to the vertical mean) in the warm rain region connected to sinking motion in the cold rain region. The upper cell is found above the 0°C level, with induced subsidence in the warm rain and dry regions, coupled to forced ascent in the deep convection region. It is that warm rain plays an important role in regulating the time scales of convective cycles, and in altering the tropical large-scale circulation through radiative–dynamic interactions. Reduced cloud–radiation feedback due to a faster autoconversion rate results in intermittent but more energetic eastward propagating Madden–Julian oscillations (MJOs). Conversely, a slower autoconversion rate, with increased cloud radiation produces MJOs with more realistic westward-propagating transients embedded in eastward-propagating supercloud clusters. The implications of the present results on climate change and water cycle dynamics research are discussed.

scholarly journals Investigating relationships between aerosol optical depth and cloud fraction using satellite, aerosol reanalysis and general circulation model data

2012 ◽  
Vol 12 (11) ◽  
pp. 30805-30823 ◽  
Author(s):  
B. S. Grandey ◽  
P. Stier ◽  
T. M. Wagner
Keyword(s):  
Aerosol Optical Depth ◽  
General Circulation Model ◽  
Optical Depth ◽  
General Circulation ◽  
Circulation Model ◽  
Cloud Fraction ◽  
Atmospheric Composition ◽  
Wet Scavenging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Reported Data

Abstract. Strong positive relationships between cloud fraction (fc) and aerosol optical depth (τ) have been reported. Data retrieved from the MODerate resolution Imaging Spectroradiometer (MODIS) instrument show positive fc–τ relationships across most of the globe. However, these relationships are not necessarily due to cloud–aerosol interactions. Using state of the art Monitoring Atmospheric Composition and Climate (MACC) reanalysis-forecast τ data, which should be less affected by retrieval artifacts, it is demonstrated that a large part of the observedfc–τ signal may be due to cloud contamination of satellite-retrieved τ. For longer MACC forecast time-steps of 24 h, which likely contain less residual cloud contamination, some negative fc–τ relationships are found. ECHAM5-HAM general circulation model (GCM) simulations further demonstrate that positive fc–τ relationships may arise due to covariation with relative humidity. Widespread negative simulated fc–τ relationships in the tropics are shown to arise due to scavenging of aerosol by precipitation. Wet scavenging events are likely poorly sampled in satellite-retrieved data. Quantifying the role of wet scavenging, and assessing GCM representations of this important process, remains a challenge for future observational studies of aerosol–cloud–precipitation interactions.

scholarly journals Simulation of tropospheric chemistry and aerosols with the climate model EC-Earth

2014 ◽  
Vol 7 (2) ◽  
pp. 1933-2006 ◽  
Author(s):  
T. P. C. van Noije ◽  
P. Le Sager ◽  
A. J. Segers ◽  
P. F. J. van Velthoven ◽  
M. C. Krol ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Atmospheric Chemistry ◽  
General Circulation ◽  
Data Exchange ◽  
Climate Model ◽  
Global Climate Model ◽  
Surface Ozone ◽  
Circulation Model ◽  
Tropospheric Chemistry

Abstract. We have integrated the atmospheric chemistry and transport model TM5 into the global climate model EC-Earth version 2.4. We present an overview of the TM5 model and the two-way data exchange between TM5 and the integrated forecasting system (IFS) model from the European Centre for Medium-Range Weather Forecasts (ECMWF), the atmospheric general circulation model of EC-Earth. In this paper we evaluate the simulation of tropospheric chemistry and aerosols in a one-way coupled configuration. We have carried out a decadal simulation for present-day conditions and calculated chemical budgets and climatologies of tracer concentrations and aerosol optical depth. For comparison we have also performed offline simulations driven by meteorological fields from ECMWF's ERA-Interim reanalysis and output from the EC-Earth model itself. Compared to the offline simulations, the online-coupled system produces more efficient vertical mixing in the troposphere, which likely reflects an improvement of the treatment of cumulus convection. The chemistry in the EC-Earth simulations is affected by the fact that the current version of EC-Earth produces a cold bias with too dry air in large parts of the troposphere. Compared to the ERA-Interim driven simulation, the oxidizing capacity in EC-Earth is lower in the tropics and higher in the extratropics. The methane lifetime is 7% higher in EC-Earth, but remains well within the range reported in the literature. We evaluate the model by comparing the simulated climatologies of surface carbon monoxide, tropospheric and surface ozone, and aerosol optical depth against observational data. The work presented in this study is the first step in the development of EC-Earth into an Earth system model with fully interactive atmospheric chemistry and aerosols.

scholarly journals Evaluation of autoconversion and accretion enhancement factors in general circulation model warm-rain parameterizations using ground-based measurements over the Azores

2018 ◽  
Vol 18 (23) ◽  
pp. 17405-17420 ◽  
Author(s):  
Peng Wu ◽  
Baike Xi ◽  
Xiquan Dong ◽  
Zhibo Zhang
Keyword(s):  
General Circulation ◽  
Climate Models ◽  
Climate Modeling ◽  
Circulation Model ◽  
General Circulation Models ◽  
Precipitation Intensity ◽  
Equivalent Model ◽  
Warm Rain ◽  
Enhancement Factors ◽  
Precipitating Clouds

Abstract. A great challenge in climate modeling is how to parameterize subgrid cloud processes, such as autoconversion and accretion in warm-rain formation. In this study, we use ground-based observations and retrievals over the Azores to investigate the so-called enhancement factors, Eauto and Eaccr, which are often used in climate models to account for the influence of subgrid variance of cloud and precipitation water on the autoconversion and accretion processes. Eauto and Eaccr are computed for different equivalent model grid sizes. The calculated Eauto values increase from 1.96 (30 km) to 3.2 (180 km), and the calculated Eaccr values increase from 1.53 (30 km) to 1.76 (180 km). Comparing the prescribed enhancement factors in Morrison and Gettleman (2008, MG08) to the observed ones, we found that a higher Eauto (3.2) at small grids and lower Eaccr (1.07) are used in MG08, which might explain why most of the general circulation models (GCMs) produce too-frequent precipitation events but with too-light precipitation intensity. The ratios of the rain to cloud water mixing ratio (qr/qc) at Eaccr=1.07 and Eaccr=2.0 are 0.063 and 0.142, respectively, from observations, further suggesting that the prescribed value of Eaccr=1.07 used in MG08 is too small to simulate precipitation intensity correctly. Both Eauto and Eaccr increase when the boundary layer becomes less stable, and the values are larger in precipitating clouds (CLWP>75 gm−2) than those in non-precipitating clouds (CLWP<75 gm−2). Therefore, the selection of Eauto and Eaccr values in GCMs should be regime- and resolution-dependent.

scholarly journals Interpreting the cloud cover – aerosol optical depth relationship found in satellite data using a general circulation model

2010 ◽  
Vol 10 (13) ◽  
pp. 6129-6135 ◽  
Author(s):  
J. Quaas ◽  
B. Stevens ◽  
P. Stier ◽  
U. Lohmann
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Satellite Data ◽  
General Circulation ◽  
Cloud Cover ◽  
Climate Model ◽  
Circulation Model ◽  
Total Cloud Cover ◽  
Positive Correlation ◽  
Depth Relationship

Abstract. Statistical analysis of satellite data shows a positive correlation between aerosol optical depth (AOD) and total cloud cover (TCC). Reasons for this relationship have been disputed in recent literature. The aim of this study is to explore how different processes contribute to one model's analog of the positive correlation between aerosol optical depth and total cloud cover seen in the satellite retrievals. We compare the slope of the linear regression between the logarithm of TCC and the logarithm of AOD, or the strength of the relationship, as derived from three satellite data sets to the ones simulated by a global aerosol-climate model. We analyse model results from two different simulations with and without a parameterisation of aerosol indirect effects, and using dry compared to humidified AOD. Perhaps not surprisingly we find that no single one of the hypotheses discussed in the literature is able to uniquely explain the positive relationship. However the dominant contribution to the model's AOD-TCC relationship can be attributed to aerosol swelling in regions where humidity is high and clouds are coincidentally found. This finding leads us to hypothesise that much of the AOD-TCC relationship seen in the satellite data is also carried by such a process, rather than the direct effects of the aerosols on the cloud fields themselves.

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