Radiative effects of upper tropospheric clouds observed by Aura MLS and CloudSat

Abstract

The radiative effects of upper tropospheric (UT) clouds observed by CloudSat and Aura MLS during June-July-August 2008 are examined and contrasted. We find that the UT cloud occurrence frequency observed by MLS is more than CloudSat by 4-10% in the tropical average and by 40∼60% near the tropopause in the deep convective regions. The clouds detected by MLS but missed by CloudSat (denoted as TCC) typically have visible optical thickness less than 0.2. TCC produce a tropical-mean net warming of 3.5 W/m2 at the top-of-atmosphere and net cooling of 1.2 W/m2 at the surface. They induce a net radiative heating in the UT. Their heating rate at 200 hPa is ∼0.35 K/day in the tropical-mean and ∼0.8 K/day over South Asia, which is about 3-4 times the clear-sky radiative heating rate. Hence, they are potentially important in affecting the mass transport rates from the troposphere to the stratosphere. Copyright 2009 by the American Geophysical Union.