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Quantifying the Enhancement of Tropical Precipitation due to Mesoscale Convective Organization

Presentation Date
Wednesday, January 26, 2022 at 4:45pm
Location
George R. Brown Convention Center - Remote
Authors

Author

Abstract

The fundamental dynamics of mesoscale convective organization, as well as the effects of organization on tropical precipitation, remain poorly understood. Previous studies, utilizing distinct methodologies for the quantification and characterization of organization over domains, have reached mixed and sometimes contradictory conclusions as to the relationship between convective organization and the strength of precipitation. This study seeks to provide quantitative, observational constraints on the enhancement of precipitation due to convective organization. We isolate and diagnose the enhancement of tropical precipitation attributable to mesoscale convective organization by using NASA Tropical Rainfall Measurement Mission precipitation and rain type data. Utilizing the organization index of Tompkins and Semie (2017) to quantify the degree of mesoscale convective organization, we analyze tropical precipitation by binning our data by both the column relative humidity (CRH) and convective area fraction (CAF) of the domains considered. Among domains with similar CRH and CAF, finding the difference in precipitation rate between those domains with organization indices in the top quartile and those with organization indices in the bottom quartile gives an estimation of the enhancement of tropical precipitation that is due solely to an increased level of organization. Using this method, we find that tropical domains with organization indices in the top quartile of domains with similar CRH and CAF have a mean precipitation rate on average 43.8% greater than those domains with organization indices in the bottom quartile. We further demonstrate that the mechanism behind this enhancement is dependent on the CRH of the domain. As the domain becomes increasingly saturated, the enhancement of precipitation shifts from being due to an enhancement of the rate of convective precipitation to being due to an enhancement of the stratiform area fraction over the domain.

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