Thursday, 13 January 2005: 11:00 AM
The role of fine-scale landscape and soil-moisture variability in convection initiation
Understanding the feedback between land-surface variability and precipitation is important because of its potential benefit in improving climate predictability. In summer, mesoscale boundaries play a critical role in the initiation of heavy precipitation. The zones of enhanced convergence along these boundaries have been recognized as areas of deep-convection initiation. The differential heating can be enhanced by heterogeneities in land-surface conditions. The land surface may have differing impacts, depending on atmospheric conditions. Small-scale ground features, such as vegetation, hillslopes, and urban or industrial areas can also have subtle impacts that can determine the exact boundary and intensity of storms.
We will present a recent results focusing on heavy precipitation associated with a dryline in the southcentral US, It is found that fine-scale (L~10 km) boundary-layer circulations that directly trigger deep convection are confined within a mesoscale region containing a deeper and more unstable PBL, and that this region is a result of a surface sensible heat-flux maximum over dry soils. They utilized the soil moisture fields from a high-resolution land data-assimilation system (HRLDAS) and from NCEP EDAS to initialize the MM5 model. Results from these and other recent research studies provide some hope that the careful treatment of land-surface physics and soil moisture in convection-resolving models can lead to increased rainfall predictability.