29 Soil moisture—precipitation feedback in the 2011 warm season drought in the Southern Great Plains

Monday, 7 January 2013
Exhibit Hall 3 (Austin Convention Center)
Hua Su, The University of Texas, Austin, TX; and R. E. Dickinson

The warm season drought in 2011 set record hot and dry conditions for the Southern Great Plains, with many places receiving less than half of its climatologic precipitation for the consecutive months from March to August. Although it's recognized that the drought could be triggered and driven by the related SST anomalies in the Pacific and Atlantic, the role played by soil moisture and other land hydrologic properties at more local scales is far less understood. To address this problem, we performed a suite of sensitivity experiments using a regional climate model. Our goal is to investigate the impacts of a given soil moisture anomaly on the precipitation development, and how these impacts interact with other local and large-scale hydro-meteorological processes. The results from the control simulation demonstrated that, our model framework captured many fundamental aspects of the drought fairly well, especially in terms of characterizing the anomalous atmospheric circulation patterns and the magnitudes of precipitation deficit. Further, the sensitivity simulations with perturbed soil moisture revealed some complicated patterns regarding the local and regional feedbacks between land and atmosphere. Generally speaking, a wetter soil enhanced warm season precipitation for the major part of the Southern Great Plains, a result consistent with previous work focusing on land-atmosphere coupling for this area. However, the strength of this feedback can vary significantly, as a function of a spectrum of land and atmospheric variables. Particularly, the response of atmospheric thermodynamic structure played an important role in shaping the pattern of soil moisture-precipitation feedback.
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