Speaker: Kevin Grise, University of Virginia

Title: Understanding the two-way interactions between cloud radiative effects and the midlatitude storm tracks

Abstract: Global climate models disagree on the magnitude of climate sensitivity, in large part due to uncertainty in cloud feedbacks. While attention has traditionally been focused on tropical and subtropical cloud feedbacks, the role of extratropical cloud processes in contributing to climate sensitivity is increasingly gaining more attention. In the first part of this seminar, I will review the dynamical controlling factors on extratropical clouds, and how they co-vary with large-scale shifts in the midlatitude jet stream and storm tracks. On average, global climate models struggle to accurately capture the observed co- variability between cloud-radiative processes and the storm tracks. I will explore the origin of these biases and related challenges that arise when trying to provide observational constraints on extratropical cloud feedbacks. In the second part of the talk, I will then discuss recent studies that conclude that cloud processes have a strong role in determining the mean-state atmospheric circulation and its response to climate change. A key focus will be on the role of cloud radiative processes in driving the strength and location of the extratropical storm tracks. Idealized model experiments show that the high- frequency interactions between cloud radiative effects and the dynamics of the storm tracks slightly damp the intensity of the storm tracks. The coupling among clouds, radiation, and dynamics thus has a modest but potentially important influence on the midlatitude storm tracks.

Bio: Kevin M. Grise is an associate professor of environmental sciences at the University of Virginia. In his work, he uses observations and computer models to understand variability and change in Earth’s atmosphere. His current research focuses on how the interaction between clouds and the jet stream might lead to important radiative feedbacks in future climate scenarios. He arrived at the University of Virginia following two years as a postdoctoral research scientist at Columbia University. Before that, he spent a year at McGill University in Montreal as a postdoctoral fellow and received his Ph.D. and M.S. in atmospheric science from Colorado State University. The recipient of a National Science Foundation Graduate Research Fellowship, Grise also served as co-author on the 2010 World Meterological Organization Scientific Assessment of Ozone Depletion. He holds a bachelor’s degree in meteorology from Penn State University.