区域耦合模式FROALS模拟的西北太平洋热带气旋潜势分布与年际变率:耦合与非耦合试验比较

热带气旋潜势指数可以合理刻画热带气旋生成的位置与范围, 被广泛应用于评估气候系统模式对热带气旋的模拟。本文使用区域海—气耦合模式FROALS对西北太平洋地区1982～2007年的积分结果, 检验了该模式对热带气旋潜势指数的气候态和年际变率模拟能力, 并从决定热带气旋潜势的五个变量角度, 分析了造成模式模拟偏差的原因。结果表明, 模式可以合理再现西北太平洋地区热带气旋潜势指数的分布, 但由于西北太平洋季风槽模拟偏弱且耦合后模拟海温偏冷, 使得耦合试验模拟的热带气旋潜势指数分布偏弱, 尽管较之单独大气模式, 其模拟的空间分布有改善。在年际变率方面, 模式可以合理再现年际变率中热带气旋潜势指数对ENSO的响应, 且耦合模式优于单独大气模式, 分析表明其原因在于耦合模式模拟的850 hPa季风槽强度与年际变率优于单独大气模式。因此区域耦合模式在模拟热带气旋指数年际变率方面相较大气模式有优势。

Distribution and Interannual Variability of Tropical Cyclone Genesis over the Western North Pacific Simulated by a Regional Coupled Model-FROALS: Comparison with an Uncoupled Model

The tropical cyclone genesis potential index (GPI) can reasonably reproduce the position and region of tropical cyclone genesis. It has been widely used as a metric to evaluate the performance of global climate models in simulating tropical cyclone genesis. In this study, the simulation of GPI over the western North Pacific (WNP) by a regional coupled model, FROALS (Flexible Regional Ocean-Atmosphere-Land System) developed by LASG (State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics)/IAP (Institute of Atmospheric Physics), was assessed and compared with a regional atmosphere model, RegCM3. The simulation bias is discussed by analyzing the five variables associated with GPI. The results show that FROALS can reproduce the spatial pattern and seasonal cycle of GPI in the WNP better than RegCM3. Compared with RegCM3, FROALS performs better in modeling the response to ENSO in the interannual variability of GPI in the WNP; this is due to the improved simulation of the intensity and interannual variability of the South China Sea monsoon trough.