92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Wednesday, 25 January 2012: 12:00 AM
The Summer Precipitation Responses to Local Soil Moisture Anomaly As Simulated by the Community Atmosphere Model (CAM): A Study in North America
Room 350/351 (New Orleans Convention Center )
Hua Su, Univ. of Texas, Austin, TX; and R. E. Dickinson

A soil moisture anomaly can have significant impacts on subsequent warm season rainfall as demonstrated by previous research with aid of General Circulation Models (GCMs). However, the decomposition of these impacts to two distinct scales, (1) large (synoptic) scale affected by general circulation patterns, (2) local scale where the thermodynamic processes play an important role, had seldom been investigated before. The current work focus on this issue, i.e., quantifying their individual and collective influences in North America, as simulated by the Community Atmosphere Model (CAM). We initialize various local soil wetness anomalies (drought or pluvial) at different climatic zones, and evaluate their impacts on rainfall from both large-scale and local-scale perspectives. The confining of soil moisture anomalies to small-scale help isolate local land effects and filters out noisy signals from possible remote feedback. We also relate the model results with previously found soil moisture-precipitation relations, especially those derived from observational studies. These relations serve as a benchmark for evaluating our GCM approach. Our research can provide important ramifications on the mechanical details via which a soil wetness anomaly can affect summer precipitation. Also we can offer a general assessment of CAM's capability in representing these impacts, particularly, by interpreting different physical functions running at large/local scale.

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