ASCAT observations of downdrafts from mesoscale convective systems

Citation:
Kilpatrick, TJ, Xie S-P.  2015.  ASCAT observations of downdrafts from mesoscale convective systems. Geophysical Research Letters.

Date Published:

2015/02

Keywords:

3314 Convective processes, 3354 Precipitation, 3360 Remote sensing, 3371 Tropical convection, convective downdrafts, scatterometry

Abstract:

Downdrafts of air cooled by evaporating raindrops are an essential component of mesoscale convective systems (MCSs). Here we use surface wind observations from the Advanced SCATterometer (ASCAT) to identify MCS downdrafts over the western equatorial Pacific Ocean as regions of horizontal wind divergence exceeding 10-4 s-1. More than 1300 downdrafts are identified over the observation period (2009–2014). The downdraft signal in the surface winds is validated with satellite measurements of brightness temperature and rainfall rate, and surface buoy measurements of air temperature; composite analysis with these measurements indicates ASCAT detects downdrafts that lag the peak convection by 8–12 h. While ASCAT resolves mesoscale downdrafts in regions of light rain, a composite against buoy air temperature indicates that ASCAT fails to resolve the stronger convective-scale downdrafts associated with heavy rainfall at squall fronts. Nevertheless, the global observations by the satellite scatterometer open a new avenue for studying MCSs.

Notes:

n/a

Website

DOI:

10.1002/2015GL063025