Joint Seminar: Physical Mechanisms of Convective Self-Aggregation in the Tropics

Idealized cloud-permitting simulations of radiative-convective equilibrium have become a popular tool for understanding the physical processes leading to horizontal variability of tropical water vapor and rainfall. When cloud-permitting models are run on large enough domains, water vapor self-organizes into moist and dry regions even in the absence of external forcing such as planetary rotation, surface inhomogeneities or large-scale wind shear. This emergent property of moist convection is referred to as "convective self-aggregation". However, the applicability of idealized simulations to nature is still unclear given that important processes are typically neglected. During this talk, we exploit spectral analysis to compactly summarize the multi-scale processes supporting convective aggregation. By applying this framework to high-resolution reanalysis data and satellite observations in addition to idealized simulations, we compare convective-aggregation mechanisms across horizontal scales and data sets. The results affirm the validity of idealized simulations as an analogy to the real world. Column moist static energy spectral tendencies share similar signs and scale-selectivity in cloud-permitting models and observations: Radiation increases variance at wavelengths above 1,000km, while advection damps variance at all wavelengths, and surface enthalpy fluxes mostly reduce variance between wavelengths of 1,000km and 10,000km.

Date

30.07.2019

Time

15:15 h

Place

Bundesstr. 53, room 022/023
Seminar Room 022/023, Ground Floor, Bundesstrasse 53, 20146 Hamburg, Hamburg

Speaker

Tom Beucler, University of California, Irvine

Chair

Bjorn Stevens

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