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april, 2018

24apr3:30 pm"Organization of Deep Convection into Large Mesoscale Systems"2018 Ogura Lecture — part of Illinois Earth Month

Event Details

Speaker: Ed Zipser, Atmospheric Sciences Professor at University of Utah

Abstract: The current generation of students cannot recall a time without cell phones or weather satellites. 50 years ago, deep convective storms were often described as small-scale (~ 10 km) in horizontal dimension. When Riehl and Malkus (1958) famously showed the importance of tropical convection to the energetics of the general circulation, they proposed a set of individual “hot towers”. Only with the advent of weather satellites did it become clear that cloud systems of ~ 100s of km (mesoscale) dominated the tropics and subtropics. They were first known by the uninformative name “cloud clusters”, later “mesoscale convective complexes”, later “mesoscale convective systems” or MCSs.

Today, thanks to decades of insightful interpretation of the massive databases from tropical and mid-latitude field campaigns, we know that the structure and behavior of MCSs differs in significant ways from that of scattered storms. The vertical heating profile is demonstrably different, and while we know this, we have yet to develop weather or climate models that can differentiate reliably between scattered (Arakawa-Schubert-type) convection and more realistic “organized” convection. Thanks to careful analysis of satellite “precipitation features”, for example Nesbitt et al. (2006), we have an increasingly accurate assessment of the global distribution of MCSs and their varying importance in different regimes over land and ocean.

This talk outlines some of the milestones along this 50-year quest for understanding of the importance of organized convection, its modeling, and its forecasting, such as improved severe weather forecasting, to which Yoshi Ogura’s life’s work made so many important contributions. However, despite these many advances, some important deficiencies remain. For example, there is no accepted definition of “organized convection”, and the environmental conditions that favor “organized convection”, or large MCSs, is still under debate. So there is work to do.


(Tuesday) 3:30 pm


Natural History Building Room 2079

1301 West Green Street Urbana, IL 61801


Department of Atmospheric Sciences