Tropical Cyclones and Equatorial Waves in a Convection-Permitting Aquaplanet Simulation with Off-Equatorial SST Maximum

Abstract

Tropical cyclogenesis can be influenced by convectively coupled equatorial waves; yet, existing datasets prevent a complete analysis of the multi-scale processes governing both tropical cyclones (TCs) and equatorial waves. This study introduces a convection-permitting aquaplanet simulation that can be used as a laboratory to study TCs, equatorial waves, and their interactions. The simulation was produced with the Model for Prediction Across Scales-Atmosphere (MPAS-A) using a variable resolution mesh with convection-permitting resolution (i.e., 3-km cell spacing) between 10oS–30oN. The underlying sea-surface temperature is given by a zonally symmetric profile with a peak at 10oN, which allows for the formation of TCs. A comparison between the simulation and satellite, reanalysis, and airborne dropsonde data is presented to determine the realism of the simulated phenomena. The simulation captures a realistic TC intensity distribution, including major hurricanes, but their lifetime maximum intensities may be limited by the stronger vertical wind shear in the simulation compared to the observed tropical Pacific region. The simulation also captures convectively coupled equatorial waves, including Kelvin waves and easterly waves. Despite the idealization of the aquaplanet setup, the simulated three-dimensional structure of both groups of waves is consistent with their observed structure as deduced from satellite and reanalysis data. Easterly waves, however, have peak rotation and meridional winds at a slightly higher altitude than in the reanalysis. Future studies may use this simulation to understand how convectively coupled equatorial waves influence the multi-scale processes leading to tropical cyclogenesis.

Tropical Cyclones and Equatorial Waves in a Convection‐Permitting Aquaplanet Simulation With Off‐Equatorial SST Maximum

“…The original model output is too large to publicly archive; instead, we provide a public data set containing the interpolated model output used in this study (Rios‐Berrios, 2023). Additionally, the model code with modifications to use the aquaplanet framework and other supporting files are provided by Rios‐Berrios (2022).…”

“…The original model output is too large to publicly archive; instead, we provide a public data set containing the interpolated model output used in this study (Rios‐Berrios, 2023). Additionally, the model code with modifications to use the aquaplanet framework and other supporting files are provided by Rios‐Berrios (2022). The IMERG data set was provided by NASA via https://disc.gsfc.nasa.gov/, the ERA5 data set was provided by NCAR's Research Data Archive (European Centre for Medium‐Range Weather Forecasts, 2019), and the IBTRACs data set was provided by NOAA's National Centers for Environmental Information (Knapp et al., 2018).…”