High-resolution Numerical Simulations of Tropical and Subtropical Convection for the NASA INCUS Mission

The INvestigation of Convective UpdraftS (INCUS), a NASA Earth Ventures Mission scheduled for launch in early 2027, will use three small satellites to deliver the first estimates of convective mass flux and its evolution within tropical and subtropical clouds. To assist the retrieval algorithm development, the INCUS team is producing a database of updrafts and their environments using high-resolution simulations of convective clouds conducted with the Weather Research and Forecasting Model (WRF) and the Regional Atmospheric Modeling System (RAMS). Specifically, case studies are selected in 15+ regions across the (sub)tropics. Each case study is simulated three times: once with RAMS (2-moment, bin-emulating microphysics) and twice with WRF (Morrison and Thompson aerosol-aware microphysics). Simulations utilize 3 nested grids, with the outermost grids having 1.6 km grid spacing and typically spanning well over 1,000 km in zonal and meridional directions. The innermost grids also have large areas (~230 km by ~230 km), with 100 m horizontal grid spacing, ~100 m vertical grid spacing, and 30 second output. 

Using this output, the Tracking and Object-Based Analysis of Clouds (tobac) algorithm is run offline to quantify the 3D evolution of storm updrafts and link them to their associated anvils and environments. The tracked updrafts and their properties are directly used in INCUS algorithm development. The model output is also run through the Community Radiative Transfer Model (CRTM) and INCUS Passive Active Microwave Simulator (PAMS) to forward model geostationary IR brightness temperatures and INCUS-observed radar reflectivity, respectively. The simulations are systematically evaluated with available observations to ensure that the output is realistic and to identify gaps in the model database in terms of observed convective environments, updraft profiles, storm morphologies, and reflectivity profiles. 

The goals of this talk are to: (1) give an overview of the INCUS LES database and its role in the INCUS mission; (2) provide statistics about the global nature of tropical and subtropical convection obtained using high-resolution models; and (3) showcase results from evaluation of the database against different observational datasets. The multi-model, high-resolution INCUS simulation database continues to grow as more simulations are completed and will be a useful resource for the community for understanding tropical and subtropical convective clouds.