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Report of CMAI Breakout at MAP Meeting
7-9 March 2007


CMAI: Participants | Meetings | Draft Workplan | Investigations

The CMAI investigators met for one hour at the recent MAP Meeting to discuss the re-organization of their work into three study themes: the Pacific Cross-Section (PAC) study, the Cyclone Lifecycle (CYC) study and the Arctic Clouds (ARC) study (see description below). The main question to be addressed by each group of investigations was confirmed:

PAC: What determines the variability of clouds and convection and what determines the transitions in convective style over the cross-section?
CYC: What controls the locations of cyclogenesis and cyclolysis and how do cloud processes affect the evolution of these storms?
ARC: What role do aerosols and phase changes in Arctic clouds play in the formation and evolution of Arctic cloudiness and their effect on the atmospheric moisture budget?

The following assignments of the CMAI participants to these teams were also agreed to.

PAC: J.Teixeira/P.Rasch (leader), J.Alexander, A.Barros, L.Di Girolamo, L. Donner, J. Hack, J.Luo, S.Klein/G.Potter, W-K.Tao/J.Chern, B.Soden, D.Waliser, K-M.Xu, M.Zhang
CYC: G.Tselioudis (leader), X.Dong, P.Minnis, R.Pincus, D.Posselt, B. Xi
ARC: J.Curry (leader), P. DeMott, L.Donner, V.Khvorostyanov, D. Koch, S.Kreidenweis, G.McFarquhar, S.Menon, Morrison, J.Kay

Several investigations agreed to contribute their model outputs and data analysis products to ALL three studies: model outputs from MERRA (M.Rienecker/J.Bacmeister) and ModelE (A.Del Genio) as well as from the MMF runs of W-K.Tao and the CAPT experiments from S.Klein/G.Potter and data analysis products from CloudSat (CALIPSO) from G.Stephens, MODIS analysis from P.Minnis, CERES from B.Wielicki, ISCCP from W.Rossow and results from K-M.Xu. As much as is possible, these results will cover the period from mid-2005 to mid-2007; climatologies of significant features of the cloud behavior will be constructed later. All of these results, along with other available reanalysis and satellite analyses, are to be collected on the CMAI site that is part of the GEWEX Cloud System Study – Data Integration for Model Evaluation website.

The ARC group had a further meeting and organized their efforts around four investigations: developing a comprehensive parameterization for ice nucleation, evaluating available representations of cloud particle nucleation, examining observations and theory for cloud particle size spectra and evaluating existing aerosol parameterizations and how they will interface with cloud microphysics schemes.

Re-Organization of CMAI Activities

The original MAP NRA and the definition of CMAI within did not really describe a "science question" driven activity but more an activity to improve weather and climate models (develop parameterizations) and demonstrate (by using) the utility of NASA observations for this purpose. At the first CMAI workshop, a working approach was outlined that included NASA-supported personnel to assist the CMAI investigators with acquiring satellite datasets and with conducting experiments in one of the three NASA-supported models (WRF at Marshall, GMAO at Goddard and ModelE at GISS). Since then, CMAI research activities have been carried out by the Pis working separately with little sign that any of this support has been requested. While interesting science will likely be obtained in this way, there will be little progress on the actual goals of the program, using NASA satellite datasets to improve model representations of clouds. To focus and coordinate CMAI research better and to foster a more team-oriented approach that can make more progress on developing model parameterizations, we propose forming three teams around the following concepts/science questions:

(1) the Pacific Cross-Section (PAC, led by Joao Teixeira)
(2) the Cyclone Lifecycle (CYC, led by George Tselioudis)
(3) Arctic Clouds (ARC, led by Judy Curry)

Definition of the regime transitions encompassed

The idea is that each of these projects encompasses significant changes of cloud-meteorological regime as part of the global atmospheric circulation. By working to understand the controlling factors for these changes, we can forge more direct linkages of “small-scale” studies (i.e., field experiments and higher-resolution satellite observations together with microphysical, LES and CRM modeling activities) with “large-scale” studies (i.e., global atmospheric and cloud observations from satellites together with regional to global circulation models of both weather and climate-scale variations). The Pacific Cross-Section study (PAC) would focus attention on boundary layer mixing and convection, particularly the transition from shallow convection (stratocumulus to cumulus) to deep convection in the low-latitude marine environment, both how the clouds are formed in these regimes and how convective-cloud processes couple to the large-scale tropical circulation. The Cyclone Lifecycle study (CYC) would focus on the evolution of midlatitude cyclones and their clouds and precipitation over their entire lifecycle. The Arctic Cross-Section study (ARC) would focus on the role of aerosols and cloud phase changes in determining the Arctic atmospheric water budget. Each of these teams would work towards better representations of these transitions in global models.

Science Questions to be Addressed by the Studies

Pacific Cross-Section: What determines the variability of clouds and convection and what determines the transitions in convective style over the cross-section? The modeling focus would be to determine how various models (Climate, LES, CRM) respond to a variety of large-scale and surface forcings and to develop improved cloud and convection parameterizations that capture the changes of convective style over the cross-section.

This study should capitalize on the combination of profiling instruments on TRMM, CloudSat/Calipso and AQUA to quantify the large-scale variations in vertical structure of low-latitude cloud systems.

Cyclone Lifecycle Cross-Section: What controls the locations of cyclogenesis and cyclolysis and how do cloud processes affect the evolution of these storms? The modeling focus would be to determine how various models represent the cyclone lifecyle and its associated clouds and precipitation and to develop improved cloud-precipitation physics parameterizations that capture their evolution over the cyclone lifecycle.

There are two possibilities. The first is cyclogenesis to cyclolysis in the West to East Atlantic or West to East Pacific and one, where there are fairly large differences of clouds, radiation and precipitation between the two ends of the cross-sections implying a regime transition related to storm dynamics and potentially to water transport/microphysics issues. There may be some justification to look into aerosol effects here as the aerosol concentrations peak at the western ends of the two basins. The second is an ocean-land cross-section that could stretch from the waters off the US Pacific coast to the dry regions east of the Rockies. There is a big precipitation transition along this section that is probably orographically induced but may also relate to surface fluxes and could be interesting to examine from the different points of view. This study should capitalize not only on the combinations of new satellite observations, such as CloudSat/Calipso, but also on the intense work going on to improve weather forecasting in midlatitudes that provides improved analyses of satellite sounder and wind products together with advances in atmospheric analysis.

Arctic Cross-Section: What role do aerosols and phase changes in Arctic clouds play in the formation and evolution of Arctic cloudiness and their effect on the atmospheric moisture budget? The modeling focus would be to determine the essential factors controlling water vapor and cloud behavior in the Arctic environment and to develop parameterizations that better represent aerosol and cloud phase changes and interactions.

This study should capitalize on CloudSat/Calipso (A-train) observations and the plethora of ground based radar/lidar/aerosol stations in the Arctic associated with IPY. Two cross sections will be configured, one across the Eastern Arctic and the other across the Western Arctic. Case studies will be selected to encompass both background aerosol as well as "events" such as desert dust episode, pollution aerosol, and forest fires. A hierarchical modeling approach will be used that includes parcel models, single column models, cloud resolving models, and the WRF. The hierarchical approach will be used to compare and evaluate individual cloud microphysics parameterization elements as well complete microphysical schemes and their performance in the WRF. A key element of our investigations will be to assess the optimal number of prognostic variables in bulk microphysics scheme to allow the necessary interactions with the atmospheric aerosol in order to correctly simulate the cloud and radiative properties and their interactions with the atmospheric dynamics.


CMAI: Participants | Meetings | Draft Workplan | Investigations