The Land‐Ocean Contrast in Deep Convective Intensity in a Global Storm‐Resolving Model

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Abstract
Observations reveal a clear difference in the intensity of deep convection over tropical land and ocean. This observed land‐ocean contrast provides a natural benchmark for evaluating the fidelity of global storm‐resolving models (GSRMs; global models with horizontal resolution on the order of kilometers), and GSRMs provide a potentially valuable tool for probing unresolved scientific questions about the origin of the observed land‐ocean contrast. However, land‐ocean differences in convective intensity have received relatively little attention in GSRM research. Here, we show that the strength of the land‐ocean contrast simulated by GSRMs is strongly sensitive to details of GSRM implementations, and not clearly governed by any of several hypothesized drivers of the observed land‐ocean contrast. We first examine DYAMOND Summer GSRM simulations, and show that only a subset produce a clear land‐ocean contrast in the frequency of strong updrafts. We then show that the use of a sub‐grid shallow convection scheme can determine whether or not the GSRM X‐SHiELD produces a clear land‐ocean contrast. Finally, we show that three putative drivers of the observed land‐ocean contrast (convective available potential energy, boundary layer depth, and microphysics) fail to explain why a land‐ocean contrast is present in X‐SHiELD simulations with sub‐grid shallow convection disabled. These results provide encouraging evidence that GSRMs can mimic the observed land‐ocean convective intensity contrast. However, they also show that their ability to do so can be sensitive to uncertain sub‐grid parameterizations, and suggest that existing theory may not fully capture drivers of the land‐ocean contrast simulated by some GSRMs.
Funding Information
  • Climate Program Office (03‐01‐07‐001)

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