Pentad Analysis of Summer Precipitation Variability over the Southern Great Plains and Its Relationship with the Land-surface

Sumant Nigam University of Maryland

Category: Atmospheric State & Surface

Working Group: Cloud-Aerosol-Precipitation Interaction

State-of-the-art atmospheric models are currently unable to simulate the multi-decade record of summer hydro-climate variations in an AMIP mode, even when anomalies are averaged over a large spatial domain (e.g., the million square-kilometer-plus Great Plains). At the center of the problem is the fact that when trying to explain summer precipitation variability, some of those models tend to prioritize local atmosphere-land-surface interactions, via evapotranspiration, over the remote effect of sea surface temperatures, via moisture fluxes. The problem is that observations indicate that at seasonal and monthly resolutions the priority of those processes is the other way around. Those differences are associated with different surface heat balances in models and observations. As a first step to understanding those differences, the present work focuses on the nature of atmosphere-land-surface interactions over the Great Plains in summer, but at pentad resolution, in order to better establish spatiotemporal relationships among the different variables. It is found that the interaction is characterized by more than one mode of variability at pentad resolution. One of those modes is associated with precipitation anomalies centered over the Southern Great Plains, although the maximum is slightly shifted to the east. When excessive precipitation occurs over the region, surface air temperature, evaporation, and net surface radiation are also reduced. An east-west gradient is apparent in the structure anomalies of evaporation and net surface radiation indicating the radiative control of evaporation.

This poster will be displayed at ASR Science Team Meeting.

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