Influences of Mesoscale Land–atmospheric Interactions on the 12-day Precipitation Episode During June 2002

In this numerical study, the coupled WRF/Noah LSM modeling system was applied at the CONUS domain (with a grid-spacing of 4-km in the finer domain), to simulate an 12-day (from 9 to 21 June 2002) warm-season precipitation episode that comprises both convection that originated over elevated heating sources near and in the lee of the Rocky Mountains and propagated into central plains and deep convection which originated in the central and southern plains. To investigate the possible role of surface forcing in exciting and maintaining deep convection, spatial distribution of soil moisture and temperature derived from different sources were used to initialize the WRF/Noah coupled model. Among them are the initial soil conditions obtained from the high-resolution land-surface data assimilation system (HRLDAS).

Preliminary analysis reveals that the antecedent evolution of temperature and moisture in the boundary layer, largely determined by daytime soil conditions, over the Colorado Rockies played an important role in triggering a nocturnal convection of 15 June near the continental divide. Also, surface conditions appear to significantly influence the development of the formation of deep convection that occurred in Kansas and Missouri on 18 June. Sensitivity tests show that drier soil moisture generally produced less precipitation in the simulation domain. We will discuss physical mechanisms that led to the differences in the deep convection by WRF initialized with different land state.