Real world and tropical cyclone world. Part I: high-resolution climate model verification

Real world and tropical cyclone world. Part I: high-resolution climate model verification

Recent global climate models with sufficient resolution and physics offer a promising approach for simulating
real-world tropical cyclone (TC) statistics and their changing relationship with climate. In the first part
of this study, we examine the performance of a high-resolution (;40-km horizontal grid) global climate
model, the atmospheric component of the Australian Community Climate and Earth System Simulator
(ACCESS) based on the Met Office Unified Model (UM8.5) Global Atmosphere (GA6.0). The atmospheric
model is forced with observed sea surface temperature, and 20 years of integrations (1990–2009) are analyzed
for evaluating the simulated TC statistics compared with observations. The model reproduces the observed
climatology, geographical distribution, and interhemispheric asymmetry of global TC formation rates reasonably
well. The annual cycle of regional TC formation rates over most basins is also well captured.
However, there are some regional biases in the geographical distribution of TC formation rates. To identify
the sources of these biases, a suite of model-simulated large-scale climate conditions that critically modulate
TC formation rates are further evaluated, including the assessment of a multivariate genesis potential index.
Results indicate that the model TC genesis biases correspond well to the inherent biases in the simulated
large-scale climatic states, although the relative effects on TC genesis of some variables differs between
basins. This highlights the model’s mean-state dependency in simulating accurate TC formation rates.

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