Seminar

Abstract

Global climate models indicate a narrowing and intensification of precipitation in the intertropical convergence zone (ITCZ) and ascending branch of the Hadley circulation in a warming climate. However, how these large-scale variations will manifest in the frequency and morphology of deep convective systems within these regions is still uncertain and has major implications for the tropical hydrologic and energy cycles. To shed light on this, we use satellite observations and reanalysis to analyze the variability in ITCZ width, tropical ascent area, and precipitation intensity in the current climate and understand how these variations are related to the population of deep convection and the joint cloud-precipitation-radiation relationships. Analysis shows a contraction and intensification of the ITCZ in the satellite-era that corresponds with a shift toward more organized deep convection as the ITCZ contracts. Column water vapor (CWV) is observed to increase in the ascending regions as they shrink, which may help support this observed shift toward larger, more aggregated deep convective systems. Further analysis of satellite cloud and radiative properties as a function of CWV shows increases in atmospheric radiative heating by deep convective systems outpace the precipitation increase, resulting in deep convective systems that heat the atmosphere more efficiently. Assuming the tropics is in approximate radiative convective equilibrium, as the dry zones expand and the ITCZ contracts, this implies the deep convective systems within the ITCZ must become more efficient at heating the atmosphere.

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Anita Rapp is an associate professor with the Department of Atmospheric Sciences at Texas A&M University. Dr. Rapp received her MSc and PhD in atmospheric science from Colorado State University in Fort Collins. She joined Texas A&M University in 2010 where she was appointed assistant professor in 2014 and associate professor in 2019. Dr. Rapp's research interests are in remote sensing of clouds and precipitation and their application in studying Earth's hydrological cycle, energy budget, and climate change. Currently, her focus is on combining data from multiple sensors to investigate intertropical convergence zone (ITCZ) deep convection and the role of shallow cumulus and stratocumulus clouds in the tropics and subtropics.