For the 2011 Northeast Tropical Conference
Cloud system-resolving simulations and a simple model of an
idealized Walker cell
Jonathan Wofsy and Zhiming Kuang
Department of Earth and Planetary Sciences and School of Engineering and Applied Sciences, Harvard University
Abstract
An idealized Walker cell with prescribed sea surface temperature (SST)
is studied using both a two-dimensional cloud system-resolving model
(CSRM) and a simple conceptual model. For simplicity, radiative
cooling is prescribed in the CSRM. For the same SST distribution, the
Walker cell varies systematically with the magnitude of the radiative
cooling, transitioning between a single-peak precipitation and a
double-peak precipitation distribution. A simple model is constructed
to interpret these behaviors. Key aspects of the simple model include:
a surface wind determined from boundary layer momentum budget, which
in turn sets evaporation assuming a spatially uniform surface relative
humidity, prescribed gross moist stability as a function of column
water vapor and precipitation, and a gustiness feedback on evaporation
in areas of precipitation.
Zhiming Kuang <kuang@fas.harvard.edu>