HR: 08:15h
AN: A31D-02    [Abstracts]
TI: Lagrangian Diagnostics of Tropical Deep Convection and its Effect Upon Upper-Tropospheric Humidity
AU: * Horvath, A
EM: ahorvath@rsmas.miami.edu
AF: Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
AU: Soden, B J
EM: bsoden@rsmas.miami.edu
AF: Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, United States
AB: This study combines geostationary water vapor imagery with optical cloud property retrievals and microwave sea surface observations in order to investigate in a Lagrangian framework (i) the importance of cirrus anvil sublimation on tropical upper-tropospheric humidity, and (ii) the sea surface temperature dependence of deep convective development. Although an Eulerian analysis shows a strong spatial correlation of 0.8 between monthly mean cirrus ice water path and upper-tropospheric humidity, the Lagrangian analysis indicates no causal link between these quantities. The maximum upper-tropospheric humidity occurs approximately 5 hours after peak convection, closely synchronized with the maximum cirrus ice water path, and lagging behind it by no more than 1.0 hour. Considering that the characteristic e-folding decay time of cirrus ice water is determined to be about 4 hours, this short time lag does not allow for significant sublimative moistening. Furthermore, a tendency analysis reveals that cirrus decay and growth - in terms of both cloud cover and integrated ice content - is accompanied by drying and moistening of the upper troposphere, respectively, a result opposite that expected if cirrus ice were a primary water vapor source. In addition, it is found that an 2 degree-C rise in sea surface temperature results in a measurable increase in the frequency, spatial extent, and water content of deep convective cores. The larger storms over warmer oceans are also associated with slightly larger anvils than their counterparts over colder oceans; however, anvil area per unit cumulus area, that is, cirrus detrainment efficiency decreases as SST increases.
DE: 0365 Troposphere: composition and chemistry
DE: 3310 Clouds and cloud feedbacks
DE: 3314 Convective processes
DE: 3360 Remote sensing
DE: 3374 Tropical meteorology
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting