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Understanding Tropical Subseasonal Convection in E3SM Version 2 Using Process-Oriented Diagnostics

Presentation Date
Monday, January 9, 2023 at 5:00pm - Monday, January 9, 2023 at 6:30pm
Colorado Convention Center - Hall A



Despite decades of research and advancements in theoretical understanding, the capability of many global climate models in simulating the Madden-Julian oscillation and other tropical convectively coupled disturbances remains unsatisfactory. Given the strong influence that such disturbances have on weather extremes, tropical cyclone activity, and monsoon systems, improving the representation of organized tropical convection in GCMs is essential. Here, we examine tropical subseasonal convective variability in version 2 (V2) of the U.S. Department of Energy’s Energy Exascale Earth System Model (E3SM) using process-oriented diagnostics designed to highlight key feedbacks among convection, moisture, and radiation. Compared to its predecessor E3SM version 1 (V1), the newest E3SM version produces a significantly larger ratio of large-scale to convective precipitation during heavy rain events. E3SM V2 exhibits increased intraseasonal precipitation variability, which is shifted to higher frequencies when compared to E3SM V1, but convectively coupled Kelvin wave activity remains considerably less than observed. Phenomenological changes are examined in the context of model configuration updates related to treatments of atmospheric instability and deep convective triggering. The detailed diagnostics serve as an additional data point for the modeling community, providing insight on both E3SM model biases and driving mechanisms of tropical subseasonal convective variability.

11th Symposium on the Madden-Julian Oscillation and Sub-Seasonal Monsoon Variability
Funding Program Area(s)