POPC4OM: Understanding population controls on cloud-circulation coupling based on observationally-constrained modeling

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Cumulus cloud fields in the Trade wind regions play an important role in Earth's climate system, persistently covering substantial areas of the subtropical Tradewind regions. Over the years systematic biases involving cumulus parameterizations in climate models have been found to cause significant uncertainty in future climate predictions, through cloud-climate feedbacks that are still poorly understood. This reflects our prevailing lack of understanding of how cumulus cloud fields are coupled to the larger-scale environment and circulation. Recent and upcoming field campaigns in the Atlantic Tradewind regions are designed to give more insight into this problem. Two NARVAL campaigns (Next-Generation Aircraft Remote Sensing for Validation Studies) took place in 2013 and 2016, while the upcoming EUREC4A field campaign (ElUcidating the Role of Clouds-Circulation Coupling in ClimAte) is scheduled to take place in early 2020. The High Altitude and LOng-range research aircraft (HALO) plays a key role in these field campaigns, by sampling remote areas effectively and frequently. This project aims to combine HALO observations of cumulus clouds and their environment as collected during NARVAL-II and EUREC4A with high-resolution Large-Eddy Simulations and conceptual cumulus cloud population modeling. The first research objective is to create large-scale forcing datasets that are exclusively based on HALO dropsonde measurements. The second objective is to evaluate these process models against independent HALO and MODIS cloud measurements, reflecting both bulk properties and cloud population variability. The third and final objective is to use this synergy of modeling and measurements to gain more insight into the control of cumulus population dynamics on the cloud-circulation coupling in the Tradewind regions.