Cold pool collisions as a triggering mechanism of convection

Gustav Halvorsen,Bettina Meyer,Jan Härter

doi:10.5194/egusphere-egu2020-12367

Abstract

&lt;p&gt;Cold pools are produced by rain evaporation from&lt;br&gt;convective thunderstorms and play an important role&amp;#160;&lt;br&gt;in many atmospheric phenomena (e.g. transition to deep convection and convective self-aggregation). From observational&lt;br&gt;and numerical studies, it has been found that intersecting cold pools&lt;br&gt;increase the likelihood of triggering convection.&lt;br&gt;We test this hypothesis by combining observational&lt;br&gt;radar data from Darwin (Australia) with a simple conceptual model.&lt;/p&gt;&lt;p&gt;We identify precipitation objects in the radar data. It is assumed that each rain event produces a cold pool&lt;br&gt;that is initialized at the center of the precipitation cell. Cold pools are simulated with a stochastic surface growth model.&lt;br&gt;The spatial coordinate of each collision event is recorded.&amp;#160;&lt;br&gt;Collectively these points take the shape of a Voronoi diagram.&amp;#160;&lt;br&gt;According to our hypothesis, the probability of new rain events should decay with spatial distance to the Voronoi.&lt;/p&gt;&lt;p&gt;Our preliminary results suggest that rain events cluster in the&lt;br&gt;vicinity of the Voronoi with a higher frequency that one would expect if cold pool collisions did not stimulate convection.&amp;#160;&lt;br&gt;To conclude, our findings suggest that dynamic collisions between cold pools increase the likelihood of convection in the surrounding area.&lt;br&gt;This work allows us to study the effect of cold pools from radar data, despite cold pools being invisible to the radar images,&lt;br&gt;using a simple object-based model of convective cold pools.&amp;#160;&lt;/p&gt;

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