国家重点基础研究发展计划 973计划 41475055 41475061;气象预报业务关键技术发展专项YBGJXM 2018 2018KJ027国家重点基础研究发展计划（973计划）项目2015CB452804，国家自然科学基金项目41475055、41475061，气象预报业务关键技术发展专项YBGJXM（2018）1B-08、2018KJ027
State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 100081
National Basic Research Program of China 973 Program 2015CB452804;National Natural Science Foundation of China Grants 41475055 41475061;Meteorological Forecasting Operation Key Technology Development Program (Grants YBGJXM 2018 2018KJ027National Basic Research Program of China (973 Program, Grant 2015CB452804), National Natural Science Foundation of China (Grants 41475055, 41475061), Meteorological Forecasting Operation Key Technology Development Program (Grants YBGJXM (2018)1B-08, 2018KJ027)
The characteristics of ETTCs (extratropical transitioned tropical cyclones) activities and their wind and rainfall distribution were studied based on the best track data from CMA/STI (China Meteorological Administration and Joint Typhoon Warning Center), the multiplatform tropical cyclone surface wind analysis product, CMORPH (Climate Prediction Center morphing technique) satellite data provided by NOAA (National Oceanic and Atmospheric Administration) and TBB (cloud-top black body temperature) calculated by satellite observation during 1987 to 2016 over the western North Pacific. The results show that: (1) The average annual number of ETTCs was 7.6. The ETTCs could appear in every month except January and February, and peak in September. About 90.4% of the ETTCs occuring to the north of 30°N, while the others (9.6%) to the south of 30°N always occurred in the alternation of spring and summer or autumn and winter. (2) The major tracks of the ETTCs were northwestward in their early stage and then later turned northeastward or northward, and the extratropical transitions occurred after their turning. After ETs, most TCs moved faster and became weaker or maintained their intensity. Only 10.5% of ETTCs were strengthened. (3) The maximum wind of ETTCs decreased rapidly with its radius increasing, and the 34-knot wind radius of the ETTC was larger in the northern quadrant than in the southern quadrant. These indicate that the TC structure became much asymmetric and the inner core became loose during the extratropical transition. (4) The asymmetry of the ETTCs wind and rainfall distribution was enhanced during the ET process. The stronger wind tended to be on the east side of the ETTCs (right or back side along TC track, while the stronger rainfall tended to be on the north side, and the strongest rainfall moved to the outer region from the inner-core region in the northeast quadrants. (5) The asymmetric characteristics of wind and rainfall distribution had a close relationship with the strong VWS (vertical wind shear). Strong rainfall tended to be in the downshear to downshear left, and strong wind (motion-removed) tended to be in the shear left.
王佳琪,李英.西北太平洋热带气旋变性过程中的风及降水分布变化特征分析.大气科学,2019,43(6):1329~1343 WANG Jiaqi,LI Ying,.