J4.1 Linking Land-Atmosphere-Cloud Interactions to Transitions from Shallow to Deep Convective Cloud over the Southern Great Plains (Invited Presentation)

Tuesday, 8 January 2019: 3:00 PM
North 127ABC (Phoenix Convention Center - West and North Buildings)
Larry K. Berg, PNNL, Richland, WA; and J. D. Fast, W. I. Gustafson Jr., H. Xiao, S. L. Tai, Z. Feng, Y. Qian, and M. Huang

The US Department of Energy’s Atmospheric Radiation Measurement (ARM) Holistic Interactions of Shallow Clouds, Aerosols, and Land-Ecosystems (HI-SCALE) field campaign conducted in the spring and late summer of 2016 provides a detailed set of aircraft and surface measurements that enable a more complete understanding of land-atmosphere-cloud interactions and improved parameterizations of the lifecycle of shallow clouds. On August 30, shallow cumulus formed over the central United States around 1145 LST and two aircraft missions were conducted to obtain in situ measurements of boundary-layer and cloud properties, which are augmented by surface and subsurface measurements of energy fluxes and soil moisture associated with the ARM Southern Great Plains (SGP) site and Oklahoma Mesonet. Satellite images indicated that shallow convection initially formed over eastern and southeastern Oklahoma around 0945 LST and spread over the entire state and southeastern Kansas over the next two hours. As the day progressed, shallow clouds transitioned to short-lived deeper convection that produced precipitation in some areas with generally smaller values of soil moisture. A complex population of convective clouds was observed over Oklahoma by late afternoon, suggesting that this day would be useful to examine the impact of land-atmosphere-cloud interactions. In this study, we utilize a Large-Eddy Simulation (LES) conducted using the Weather Research and Forecasting (WRF) model for August 30. Our simulations use a relatively large domain that is ~120 km wide and a nested grid approach with a modified version of surface and subsurface properties so that the model can represent a more complex evolution of the surface and subsurface properties, surface fluxes, environmental forcing, and cloud population. The simulations are evaluated using routine in situ and remotely-sensed ARM observations and HI-SCALE aircraft observations, including surface heterogeneity, surface fluxes, vertical velocity distribution, cloud depth, and cloud fraction. Additional insight in the model performance is obtained using a data set derived from the ARM Total Sky Imager (TSI) and application of an advanced cloud tracking algorithm. Our result demonstrates that the LES incorporating the surface heterogeneity can capture the observed cloud fields, therefore serving as a powerful tool to advance our scientific understanding on the dynamics of Land-Atmosphere-Cloud Interactions over SGP.
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