Tropical Cyclones in Global Storm-Resolving Models

Abstract

Recent progress in computing and model development has initiated the era of global storm-resolving modeling and with it the potential to transform weather and climate prediction. Within the general theme of vetting this new class of models, the present study evaluates nine global-storm resolving models in their ability to simulate tropical cyclones (TCs). Results show that, broadly speaking, the models produce realistic TCs and remove longstanding issues known from global models such as the deficiency to accurately simulate TC intensity. However, TCs are strongly affected by model formulation, and all models suffer from unique biases regarding the number of TCs, intensity, size, and structure. Some models simulated TCs better than others, but no single model was superior in every way. The overall results indicate that global storm-resolving models are able to open a new chapter in TC prediction, but they need to be improved to unleash their full potential.

Convection‐Permitting Simulations With the E3SM Global Atmosphere Model

“…A key advantage of running global convection‐permitting models is the ability to represent and study multiscale interactions between the inner structure of tropical cyclones and the large‐scale environment (Satoh et al., 2019). In the first phase of the DYAMOND project, models produced a wide range of tropical cyclone counts and intensities with counts as low as four to as high as 20, while in reality there were 14 (Judt et al., 2021; Stevens et al., 2019). In this section, we provide a brief and broad overview of the tropical cyclones identified in the SCREAM simulation.…”

“…Tropical cyclones (TCs) are some of the most intense storms in the world, combining intense precipitation with winds frequently in excess of 30 m s −1 . Although some global models are able to represent TC frequency and intensity well at 0.25° grid spacing, resolving the inner structure of these storms requires much finer resolution (Judt et al., 2021; Wehner et al., 2014; Zarzycki & Jablonowski, 2015). A key advantage of running global convection‐permitting models is the ability to represent and study multiscale interactions between the inner structure of tropical cyclones and the large‐scale environment (Satoh et al., 2019).…”

“…More analysis is necessary for an in depth study of the storm characteristics in SCREAM, as was done by Judt et al. (2021) for the models participating in the first phase of DYAMOND. However, as Figures 19 and 20 indicate, SCREAM produces tropical cyclones with reasonable eye‐wall structure and adequate surface wind intensities, which provide promise for future attempts to simulate observed tropical cyclones using the model.…”

“…Because finer grid spacing allows smaller spatial and temporal scales to be resolved, higher‐resolution GCMs also better capture extreme precipitation events (Iorio et al., 2004; Terai et al., 2018; Wehner et al., 2014). As GCM grid spacing falls to 25 km or less, tropical cyclones begin to be resolved (Atlas et al., 2005; Bacmeister et al., 2014; Caldwell et al., 2019; Wehner et al., 2014), though capturing details of spatial structure requires still finer resolution (Judt et al., 2021). Some classic model problems are, however, relatively unaffected by reducing grid spacing to 25 km.…”

Tropical Cyclone Frequency

“…Increasing resolution in both atmospheric and ocean models holds promise as a route to alleviating biases in simulated TC activity, including those associated with atmosphere-ocean coupling as well as those associated with representing the TCs per se, particularly as the representation of unresolved processes, including convection, remains uncertain in simulating and projecting TC frequency. Although global cloud resolving (kilometer-scale) models have been developed (e.g., Judt et al, 2021;Satoh et al, 2019), the duration of the simulations performed with these models are typically shorter than what is needed for TC projections.…”