Tropical deep convection can aggregate into large clusters, which can have impacts on the local humidity and precipitation. Sea surface temperature (SST) gradients have been shown to organize convection, yet there has been little work done to investigate the impact of diabatic heating perturbations in the atmosphere on the aggregation of convection. Here we investigate how anomalous diabatic heating of the atmospheric column, through an idealized aerosol plume, affects the existence and mechanisms of convective aggregation in non-rotating, global radiative-convective equilibrium simulations. We show that the aerosol forcing has the ability to increase the degree of aggregation, especially at lower SSTs. Detailed investigation shows that the diabatic heating source incites a thermally driven circulation, forced by the shortwave perturbation. The increase in aggregation is caused in part by this circulation, and in part by the longwave heating anomalies occurring due to the surface convergence of moisture and convection. At higher SSTs, longwave feedbacks are crucial for the aggregation of convection, even with the shortwave heating perturbation. At lower SSTs, convection is able to aggregate with the shortwave perturbation in the absence of longwave feedbacks. These perturbations provide a link to studying the effects of absorbing aerosol plumes on convection, for example during the Indian monsoon season. We argue that, as there is aggregation for plumes with realistic aerosol absorption optical depths, this could be an analogue for real-world organization in regions with high pollution.
Bibliographical noteFunding Information:
The authors thank Aiko Voigt and an anonymous reviewer who helped to improve the manuscript significantly. B. D. acknowledges funding from the Natural Environment Research Council, Oxford DTP, Award NE/L002612/1. G. D. and P. S. acknowledge funding from the European Research Council project RECAP under the European Union's Horizon 2020 research and innovation program with grant agreement 724602. P.S. additionally acknowledges funding from the Natural Environment Research Council project NE/L01355X/1 (CLARIFY) and from the FORCeS project under the European Union's Horizon 2020 research program with grant agreement 821205. Computations and data processing have been performed on the ARCHER and JASMIN computing facilities. The authors also thank Sara Shamekh and Caroline Muller for the useful discussions during the preparation of this paper. The authors thank the Center for Environmental Data Analysis (CEDA) Archive for hosting our model output data, which is freely available in NetCDF format online at http://dx.doi.org/10.5285/1a86e0326e1346febf121eca83bf1f08 .
© 2021 The Authors. Journal of Advances in Modeling Earth Systems published by Wiley Periodicals LLC on behalf of American Geophysical Union.
- aerosol-cloud interactions
- convective organization
- tropical convection