Abstract:In this study, a new concept of multi timescale heavy rainfall reinforcement (HRR) and extreme heavy rainfall reinforcement (EHRR) associated with tropical cyclones (TCs) based on Euler coordinate method are defined to study coastal areas. The 1 h, 3 h, 6 h, 12 h, and 24 h accumulated rainfall increment data of 135 TCs which influenced Zhejiang Province from 1973 to 2015 are extracted from hourly precipitation data of 67 national stations in Zhejiang Province, and the TC center location and intensity information of the above mentioned precipitation samples are also extracted from the China Meteorological Administration tropical cyclone best track datasets. Statistical results show that the thresholds of EHRR are 29.1, 51.9, 88.3, 103.9 and 123.9 mm over 1 h, 3 h, 6 h, 12 h, and 24 h, respectively. The frequencies of HRR under different temporal resolutions have similar seasonal variation, interannual variation and long term linear trend, but the diurnal variation is different. The HRR and EHRR occur mainly in the eastern coastal area of Zhejiang in which the southern part of Wenzhou and the southern part of Taizhou are the highest frequency areas. HRR is likely to occur with 9 kinds of typhoon tracks which influenced Zhejiang. Except for the tracks by which TCs landed north of Zhoushan, EHRR could happen with the other tracks. The kind of track by which TC landed between Jiaojiang and Fuqing occupies the most percent of frequency of HRR and EHRR. Most of the TC centers concentrate in the border of Wenzhou and Taizhou in Zhejiang and northeast coast of Fujian when HRR and EHRR happened. The high frequency of HRR and EHRR at different timescales has different distance away from the TC center, but the maximum value of TC HRR appears in the range of typhoon center 600-700 km. The highest frequency of HRR and EHRR occurs in the northeast quadrant under different temporal resolutions, followed by the northwest quadrant, and the most significant reinforcements occur in the northeast quadrant. In addition, HRR and EHRR are related to the intensity of TC. On average, the most likely occurrence of RRTC is the strong tropical storm level, and ERRTC is the tropical depression level.