Diagnosis of Convective Organization and Cold Pools using ARM Datasets and Evaluation of a Unified Convection Parameterization (UNICON)

Principal Investigator(s):
Daehyun Kim, University of Washington

Angela Rowe, University of Washington
Sungsu Park, Seoul National University

Wei-Yi Cheng, University of Washington

Studies have revealed the important role of cold pools in the transition from shallow to deep and organized convection. It has been suggested that evaporatively-driven boundary layer cold pools facilitate the convective organization process by promoting subsequent convection over a limited domain near their edges.  These results highlight the need for global climate models (GCMs) to represent mesoscale convective organization and cold pools to correctly simulate phenomena in which these processes are important (e.g., the diurnal cycle of precipitation and the Madden-Julian Oscillation). While a few models have started to include mesoscale convective organization and cold pools, most GCMs still lack a representation of these processes due to limited understanding of the two-way feedback between convective organization and cold pools.

In the proposed research, Atmospheric Radiation Measurement (ARM) Climate Research Facility observations collected during recent field campaigns, augmented by high-resolution Weather Research and Forecasting (WRF) model simulations, will be used i) to improve understanding of the mesoscale convective organization and cold pool processes in continental (MC3E ARM campaign) and maritime (AMIE ARM campaign) environments, and ii) to evaluate a unified convection scheme (UNICON), which is one of the recent parameterization schemes that explicitly represent the processes. Ground-based radar observations will be used for a feature-based identification of convection to quantify the degree of mesoscale organization in an objective manner and for identification of precipitation-generated cold pools. Surface meteorology products will be used to deduce cold pool properties, such as temperature and humidity perturbations. Time evolution of cold pool properties will be compared with the evolution of convective organization to infer the feedback between them under different environmental contexts. ARM observation-driven WRF simulations will be performed and will be used as a secondary reference dataset. Results of the diagnostic work will be used to constrain aspects of UNICON, which is a convection scheme of interest to the new DOE climate model under the ACME (Accelerated Climate Modeling for Energy) project. A single column version of the ACME model will be forced by ARM observations for the MC3E and AMIE periods. Comparisons of the key parameterized processes associated with convective organization and cold pools against those derived from ARM observations and the WRF simulations will be performed to investigate systematic biases in those key parameterized quantities and their causes.

The proposed research will contribute to advancing our understanding of mesoscale convective organization and cold pool processes and to improving parameterization of these interacting processes, which can be used in any global model with parameterized convection.