Spontaneous convective aggregation in the tropics – Is it important and is it real?

Online seminar by Dr. Adrian Tompkins from ICTP - International Centre for Theoretical Physics Trieste, Italy

16 March 2022
KST 16:00 – 17:00

Join us online: https://pusan.zoom.us/j/81784269152?pwd=c1MxWTJ3VXZKUGl6UFArS3FXRFplQT09 Meeting ID: 817 8426 9152 Passcode: 817769

This talk will present the concept of convective aggregation on the mesoscale in idealized cloud resolving models, in highly simplified stochastic models and in the latest observations in the tropical western Pacific.

Cloud resolving models run in idealized conditions of radiative convective equilibrium often show randomly distributed convection switching to a state in which the convection is highly clustered, leading to a much drier mean state, which in turn impacts radiative

budget.  If this organization of convection is sensitive to surface temperature, it could thus represent a facet of climate sensitivity missing from the current generation of climate models.  In this talk I will first introduce the concept of convective clustering and some of the past work that has shown how diabatic feedbacks such as

cloud-radiative feedbacks and surface fluxes can lead to the phenomenon.

These experiments show that the relative strengths of the feedbacks are model dependent, and therefore to increase understanding, I will present the results of a minimal physics, stochastic reactive-diffusive model for water vapour in the tropical atmosphere, which reproduces the general behaviour of the full physics models.  Using this simplified model we derive a dimensional parameter which predicts which model parameter settings, and domain/resolution frameworks, lead to clustering or random convection.  Given that clustering occurs in idealized frameworks, the question is whether it is relevant for the real atmosphere on the mesoscale, where ocean SST contrasts driven by dynamics largely determines the large-scale distribution of convection.