Significant Contribution from Organized Deep Convection on Observed Changes in Tropical Rainfall

Abstract:

In the tropics, half of the total rainfall comes from organized deep convection. Therefore, changes in these organized systems will likely have a considerable impact on rainfall. Here, we investigate how observed changes in deep convection of different degrees of organization contribute to changes in tropical rainfall.

Cloud regimes derived from the International Satellite Cloud Climatology Project allow us to identify organized deep convection and less organized deep convection at the scale of a few hundred kilometers. By decomposing the contributions of these regimes to changes in precipitation derived from the Global Precipitation Climatology Project, we find that the change in the frequency of organized deep convection can explain most of the observed spatial patterns of change in rainfall. In contrast, changes in the mean precipitation of organized deep convection and changes in less organized forms of deep convection contribute lower to rainfall changes. Independent results based on the Tropical Rainfall Measuring Mission support our key conclusions.

Given the lack of distinction between the different degrees of organization of convection in global climate models, our results caution against the reliance on these models for future rainfall projections and highlight an area of priority for future model development to achieve a more accurate representation of precipitation.