scholarly journals Evaluating the “critical relative humidity” as a measure of subgrid-scale variability of humidity in general circulation model cloud cover parameterizations using satellite data

2012 ◽  
Vol 117 (D9) ◽  
pp. n/a-n/a ◽  
Author(s):  
Johannes Quaas
Keyword(s):  
Relative Humidity ◽  
General Circulation Model ◽  
Satellite Data ◽  
General Circulation ◽  
Cloud Cover ◽  
Circulation Model ◽  
Subgrid Scale ◽  
Critical Relative Humidity ◽  
Model Cloud

scholarly journals Cloud Vertical Distribution across Warm and Cold Fronts in CloudSat–CALIPSO Data and a General Circulation Model

2010 ◽  
Vol 23 (12) ◽  
pp. 3397-3415 ◽  
Author(s):  
Catherine M. Naud ◽  
Anthony D. Del Genio ◽  
Mike Bauer ◽  
William Kovari
Keyword(s):  
Relative Humidity ◽  
Southern Hemisphere ◽  
General Circulation Model ◽  
General Circulation ◽  
Cloud Cover ◽  
Climate Models ◽  
Storm Track ◽  
Circulation Model ◽  
Global Climate Models ◽  
Cold Fronts

Abstract Cloud vertical distributions across extratropical warm and cold fronts are obtained using two consecutive winters of CloudSat–Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) observations and National Centers for Environmental Prediction reanalysis atmospheric state parameters over the Northern and Southern Hemisphere oceans (30°–70°N/S) between November 2006 and September 2008. These distributions generally resemble those from the original model introduced by the Bergen School in the 1920s, with the following exceptions: 1) substantial low cloudiness, which is present behind and ahead of the warm and cold fronts; 2) ubiquitous high cloudiness, some of it very thin, throughout the warm-frontal region; and 3) upright convective cloudiness near and behind some warm fronts. One winter of GISS general circulation model simulations of Northern and Southern Hemisphere warm and cold fronts at 2° × 2.5° × 32 levels resolution gives similar cloud distributions but with much lower cloud fraction, a shallower depth of cloudiness, and a shorter extent of tilted warm-frontal cloud cover on the cold air side of the surface frontal position. A close examination of the relationship between the cloudiness and relative humidity fields indicates that water vapor is not lifted enough in modeled midlatitude cyclones and this is related to weak vertical velocities in the model. The model also produces too little cloudiness for a given value of vertical velocity or relative humidity. For global climate models run at scales coarser than tens of kilometers, the authors suggest that the current underestimate of modeled cloud cover in the storm track regions, and in particular the 50°–60°S band of the Southern Oceans, could be reduced with the implementation of a slantwise convection parameterization.

scholarly journals Evaluation of boundary layer cloud parameterizations in the ECHAM5 general circulation model using CALIPSO and CloudSat satellite data

2014 ◽  
Vol 6 (2) ◽  
pp. 300-314 ◽  
Author(s):  
Christine C. W. Nam ◽  
Johannes Quaas ◽  
Roel Neggers ◽  
Colombe Siegenthaler-Le Drian ◽  
Francesco Isotta
Keyword(s):  
Boundary Layer ◽  
General Circulation Model ◽  
Satellite Data ◽  
General Circulation ◽  
Circulation Model ◽  
Boundary Layer Cloud ◽  
Layer Cloud

scholarly journals Examination of aerosol distributions and radiative effects over the Bay of Bengal and the Arabian Sea region during ICARB using satellite data and a general circulation model

2012 ◽  
Vol 12 (3) ◽  
pp. 1287-1305 ◽  
Author(s):  
R. Cherian ◽  
C. Venkataraman ◽  
S. Ramachandran ◽  
J. Quaas ◽  
S. Kedia
Keyword(s):  
General Circulation Model ◽  
Temporal Resolution ◽  
Satellite Data ◽  
Bay Of Bengal ◽  
Temporal Variability ◽  
General Circulation ◽  
Arabian Sea ◽  
Large Scale ◽  
Circulation Model ◽  
Aerosol Index

Abstract. In this paper we analyse aerosol loading and its direct radiative effects over the Bay of Bengal (BoB) and Arabian Sea (AS) regions for the Integrated Campaign on Aerosols, gases and Radiation Budget (ICARB) undertaken during 2006, using satellite data from the MODerate Resolution Imaging Spectroradiometer (MODIS) on board the Terra and Aqua satellites, the Aerosol Index from the Ozone Monitoring Instrument (OMI) on board the Aura satellite, and the European-Community Hamburg (ECHAM5.5) general circulation model extended by Hamburg Aerosol Module (HAM). By statistically comparing with large-scale satellite data sets, we firstly show that the aerosol properties measured during the ship-based ICARB campaign and simulated by the model are representative for the BoB and AS regions and the pre-monsoon season. In a second step, the modelled aerosol distributions were evaluated by a comparison with the measurements from the ship-based sunphotometer, and the satellite retrievals during ICARB. It is found that the model broadly reproduces the observed spatial and temporal variability in aerosol optical depth (AOD) over BoB and AS regions. However, AOD was systematically underestimated during high-pollution episodes, especially in the BoB leg. We show that this underprediction of AOD is mostly because of the deficiencies in the coarse mode, where the model shows that dust is the dominant component. The analysis of dust AOD along with the OMI Aerosol Index indicate that missing dust transport that results from too low dust emission fluxes over the Thar Desert region in the model caused this deficiency. Thirdly, we analysed the spatio-temporal variability of AOD comparing the ship-based observations to the large-scale satellite observations and simulations. It was found that most of the variability along the track was from geographical patterns, with a minor influence by single events. Aerosol fields were homogeneous enough to yield a good statistical agreement between satellite data at a 1° spatial, but only twice-daily temporal resolution, and the ship-based sunphotometer data at a much finer spatial, but daily-average temporal resolution. Examination of the satellite data further showed that the year 2006 is representative for the five-year period for which satellite data were available. Finally, we estimated the clear-sky solar direct aerosol radiative forcing (DARF). We found that the cruise represents well the regional-seasonal mean forcings. Constraining simulated forcings using the observed AOD distributions yields a robust estimate of regional-seasonal mean DARF of −8.6, −21.4 and +12.9 W m−2 at the top of the atmosphere (TOA), at the surface (SUR) and in the atmosphere (ATM), respectively, for the BoB region, and over the AS, of, −6.8, −12.8, and +6 W m−2 at TOA, SUR, and ATM, respectively.

scholarly journals Superparameterised cloud effects in the EMAC general circulation model (v2.50) – influences of model configuration

2020 ◽  
Vol 13 (6) ◽  
pp. 2671-2694
Author(s):  
Harald Rybka ◽  
Holger Tost
Keyword(s):  
General Circulation Model ◽  
Diurnal Cycle ◽  
General Circulation ◽  
Cloud Cover ◽  
Large Scale ◽  
Current Model ◽  
Sensible Heat Flux ◽  
Circulation Model ◽  
Cloud Amount ◽  
Model Configuration

Abstract. A new module has been implemented in the fifth generation of the ECMWF/Hamburg (ECHAM5)/Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC) model that simulates cloud-related processes on a much smaller grid. This so-called superparameterisation acts as a replacement for the convection parameterisation and large-scale cloud scheme. The concept of embedding a cloud-resolving model (CRM) inside of each grid box of a general circulation model leads to an explicit representation of cloud dynamics. The new model component is evaluated against observations and the conventional usage of EMAC using a convection parameterisation. In particular, effects of applying different configurations of the superparameterisation are analysed in a systematical way. Consequences of changing the CRM's orientation, cell size and number of cells range from regional differences in cloud amount up to global impacts on precipitation distribution and its variability. For some edge case setups, the analysed climate state of superparameterised simulations even deteriorates from the mean observed energy budget. In the current model configuration, different climate regimes can be formed that are mainly driven by some of the parameters of the CRM. Presently, the simulated total cloud cover is at the lower edge of the CMIP5 model ensemble. However, certain “tuning” of the current model configuration could improve the slightly underestimated cloud cover, which will result in a shift of the simulated climate. The simulation results show that especially tropical precipitation is better represented with the superparameterisation in the EMAC model configuration. Furthermore, the diurnal cycle of precipitation is heavily affected by the choice of the CRM parameters. However, despite an improvement of the representation of the continental diurnal cycle in some configurations, other parameter choices result in a deterioration compared to the reference simulation using a conventional convection parameterisation. The ability of the superparameterisation to represent latent and sensible heat flux climatology is independent of the chosen CRM setup. Evaluation of in-atmosphere cloud amounts depending on the chosen CRM setup shows that cloud development can significantly be influenced on the large scale using a too-small CRM domain size. Therefore, a careful selection of the CRM setup is recommended using 32 or more CRM cells to compensate for computational expenses.

scholarly journals Regional Regime-Based Evaluation of Present-Day General Circulation Model Cloud Simulations Using Self-Organizing Maps

2018 ◽  
Vol 123 (8) ◽  
pp. 4259-4272 ◽  
Author(s):  
Alex Schuddeboom ◽  
Adrian J. McDonald ◽  
Olaf Morgenstern ◽  
Mike Harvey ◽  
Simon Parsons
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Circulation Model ◽  
Self Organizing Maps ◽  
Model Cloud ◽  
Self Organizing
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