[Seminar on Dec 27] Thermodynamic and Dynamic Mechanisms for Hydrological Cycle Intensification over the Full Probability Distribution of Precipitation Events
Prof. Gang Chen
University of California, Los Angeles, USA
Room 1218, Building 3, IAP
10:00, Dec 27, 2019
Precipitation changes in a warming climate have been examined with a focus on either mean precipitation or precipitation extremes, but changes in the full probability distribution of precipitation have not been well studied. In this talk, I will present a new quantile-conditional column moisture budget of the atmosphere for the full probability distribution of precipitation. Analysis is performed on aquaplanet model simulations under idealized climate warming and realistic CESM large ensemble in a warming climate. This framework is useful for understanding both instantaneous precipitation rate and precipitation accumulations over rainfall events. The thermodynamic response to climate warming can be understood as a generalized ‘‘wet get wetter’’ mechanism, in which the heaviest precipitation of the probability distribution is enhanced most from increased gross moisture stratification, at a rate controlled by the change in lower-tropospheric moisture rather than column moisture. The dynamic effect, in contrast, can be interpreted by shifts in large-scale atmospheric circulations such as the Hadley cell circulation or midlatitude storm tracks. Although similar mechanisms are at play for changes in both mean precipitation and precipitation extremes, the thermodynamic contributions of moisture transport to increases in high percentiles of precipitation tend to be more widespread across a wide range of latitudes than increases in the mean, especially in the subtropics.
Dr. Gang Chen is a professor in the department of Atmospheric and Oceanic Sciences at University of California, Los Angeles. He received his bachelor’s degree from Peking University in 2002 and Ph.D. degree from Princeton University in 2007. Prior to UCLA, he worked as postdoctoral fellow at MIT and held faculty position at Cornell University. His research area is atmospheric and climate dynamics, focusing on atmospheric circulation and chemical transport in a changing climate.