Drizzle-induced Change in the Organization of Stratocumulus

A modeling study of the precipitation-induced change in organizational patterns of stratocumulus is presented. The motivation for the pro ject stems from recent observations of coincidence of pockets of open cells (POCs) and drizzling episodes within the stratocumulus-topped boundary layer (STBL) over the Eastern Pacific. UCLA LES is first upgraded to support a simple microphysical parameterization based on Seifert and Beheng (2001) and then employed to simulate the STBL with various strengths of drizzle and constant surface fluxes to isolatedrizzle effect. An interaction of drizzle and surface is further examined by simulating the evolution of precipitable STBL with evolving sea surface temperature. Drizzle is also analyzed in terms of diabatic forcing to distinguish the importance of its components. Results support the hypothesis of drizzle-related formation of open cell circulation.

References

Seifert, A. and K. Beheng, 2001: A double-moment parameterization for simulating autoconversion, accretion and selfcollection. Atmos. Res., 59-60, 265–281.