School of Meteorology (Defense)
Some upscale effects of organized convection on regional climate - from the continental US to the tropical western Pacific
Colorado State University
01 May 2012, 3:00 PM
National Weather Center, Room 1350
120 David L. Boren Blvd.
University of Oklahoma
Over the continental US, the diurnal elevated heating over the Rockies generates potential vorticity anomalies that are advected downstream. Our observational and theoretical study suggests that these drifting PV anomalies are related to the movement and systematic regeneration of MCSs over the Great Plains and Midwest. These organized convective events play an important role in regional warm season rainfall climatology.
Over the tropical western Pacific, our study of satellite rainfall and SST data found that a strong excitation signal of convection is consistent with the presence of mesoscale SST gradients in ~75% of total rainfall onset events. The Laplacian of SST on scales from 50-200 km could cause horizontal PBL convergence ~3*10-5s-1, one magnitude larger than the mean regional background forcing. There is a statistical preference for excitation of rainfall on eastward-directed SST gradients. Sequences of coherent propagating rainfall events may be capable of introducing a systematic phase speed to the broader ensemble of rainfall occurrence and therefore a potential to interfere with larger scale tropical free waves or even the MJO.