School of Meteorology

Effect of aerosol on instability and convective clouds

Dr. Seoung Soo Lee
Earth System Research Laboratory

13 February 2014, 4:00 PM

National Weather Center, Room 1313
120 David L. Boren Blvd.
University of Oklahoma
Norman, OK

The conventional understanding of aerosol-cloud interactions, so-called Twomey and Albrecht effects, only focuses on microphysical modifications of clouds by aerosol with no consideration of dynamic responses to aerosol. Numerous recent studies have shown that aerosol-induced changes in feedbacks between microphysics and cloud dynamics can outweigh the effect of the instantaneous microphysical modification of clouds by aerosol regarding the response of cloud radiative properties and precipitation to aerosol. Among many factors which control the feedbacks is the atmospheric instability. The atmospheric instability determines the basic dynamic intensity of a cloud system and thus has a significant impact on the feedbacks. Recent studies have demonstrated that aerosol pollution increases the instability and invigorates convection. These studies have mostly focused on convective available potential energy (CAPE) as a measure of aerosol-induced changes in the instability. However, there is another measure of the instability which has not been investigated as much as CAPE. This different type of the measure is generally referred to as mean available potential energy (MAPE). While CAPE deals with a vertical temperature gradient, MAPE deals with a horizontal temperature gradient. This presentation shows how aerosol alters a horizontal temperature gradient or MAPE and modifies convective intensity, finally affecting the feedbacks in systems of deep convective and warm cumulus clouds.

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