ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
The Effects of La Ni?a related Sea Surface Temperature Anomalies on the Abnormal Activities of Tropical Cyclone over the North Pacific ocean in September 2022
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Abstract:
The three consecutive La Ni?a events occurred from 2020 to 2023 have been widespread concerned, which also led to various global weather and climate anomalies. By using the tropical cyclone datasets from the National Meteorological Center and the National Hurricane Center of the United States, the findings show that the number of tropical cyclones generated in the Northern Pacific in September 2022 is far more than the historical average over the same period, with the number of tropical cyclones in the Northeast Pacific reached the peak in the past 70 years. Based on the reanalysis datasets, this study analyzed the Dynamic Genesis Potential index and found that the vertical movement in the middle troposphere made a great contribution to the increased amount of tropical cyclones in the Northern Pacific. Further researches show that during the La Ni?a event, the temperature of warm pool in the Northwest Pacific continued to warm, convective activity near the Philippines enhanced and the southwesterlies over Maritime Continent strengthened, the subtropical high over the Northwest Pacific shifted northward. The emergence of low-level cyclonic circulation enhanced the ascending movement of the middle troposphere, which is favorable for the genesis of tropical cyclones. At the same time, the La Ni?a event led to an increase in the meridional temperature gradient over the Northeast Pacific, the meridional Hadley circulation being intensified, thus the upward movement over the middle and low latitudes strengthened. As the subtropical high located in western Mexico moves eastward, the number of active tropical cyclones in the Northeast Pacific increases.
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