Tropical Cyclone Genesis Potential Index over the Western North Pacific Simulated by LASG/IAP AGCM

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Supported by the National Basic Research and Development (973) Program of China (2010CB951904) and National Natural Science Foundation of China (41125017)

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  • Tropical cyclone genesis potential index (GPI) is a useful metric for gauging the performance of global climate models in the simulation of tropical cyclone (TC) genesis. The performance of LASG/IAP AGCM GAMIL2.0 in the simulation of GPI over the western North Pacific (WNP) is assessed in this paper. Since GPI depends on large scale environmental factors including low-level vorticity at 850 hPa, relative humidity at 700 hPa, vertical wind shear between 850 and 200 hPa, maximum potential intensity (MPI), and vertical velocity, the bias of GPI simulation is discussed from the perspective of thermal and dynamical factors. The results are compared with the ECMWF reanalysis data (ERA40). The analyses show that both the climatological spatial pattern and seasonal cycle of GPI over the WNP are reasonably simulated by GAMIL2.0, but due to the overestimation of relative humidity, the simulated GPI extends to 170?E, about 10?east to that in the reanalysis data. It is demonstrated that the bias in the simulation of monsoon trough, which is about 5?north to the reanalysis, leads to an overestimation of GPI during May–June and September–October, but an underestimation during July–August. Over the WNP, the response of GPI to ENSO is well captured by GAMIL2.0, including the eastward (westward) shift of TC genesis location during El Ni?no (La Ni?na) years. However, the anomalous convective center associated with El Ni?no shifts westward about 20?in comparison to ERA40, which leads to the biases in both vertical velocity and relative humidity. These eventually result in the westward deflection of the boundary between the positive and negative GPI centers along 20?–30?N. The results from this study provide useful clues for the future improvement of GAMIL2.0.
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    1. Cong Gao, Lei Zhou. Tropical cyclone genesis over the western North Pacific simulated by Coupled Model Intercomparison Project Phase 6 models. Acta Oceanologica Sinica, 2022, 41(5): 64. DOI:10.1007/s13131-021-1860-9
    2. Yixuan Shen, Yuan Sun, Zhong Zhong, et al. A Possible Cause of Tropical Cyclone Eastward Genesis Location Bias Study Using CAM5 Model in Western North Pacific. Earth and Space Science, 2020, 7(1) DOI:10.1029/2019EA000955
    3. Fuqiang Cao, Tao Gao, Li Dan, et al. Variability of Summer Precipitation Events Associated with Tropical Cyclones over Mid-Lower Reaches of Yangtze River Basin: Role of the El Niño–Southern Oscillation. Atmosphere, 2019, 10(5): 256. DOI:10.3390/atmos10050256
    4. Tianjun Zhou, Xiaolong Chen, Lu Dong, et al. Chinese contribution to CMIP5: An overview of five Chinese models’ performances. Journal of Meteorological Research, 2014, 28(4): 481. DOI:10.1007/s13351-014-4001-y

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