Characteristics of Tropical Cyclone-Induced Low-Level Wind Fields over Hainan

Using the tropical cyclone best track dataset from the Joint Typhoon Warning Center (JTWC) and the ERA-Interim reanalysis data on global 0.5°×0.5° grids from 1979 to 2015, characteristics of low-level winds around tropical cyclones (TC) over Hainan (15.5°N-23.5°N, 106°E-116°E) are statistically analyzed. Results are as follows. (1) On average, annually there are 5.5 TCs entering the study region during April to December. Most of the TCs occur over the ocean to the southeast of Hainan and their intensities are stronger than those occurred to the northwest of Hainan. (2) When the TC centers are located at different quadrants of the island, the low-level wind fields in the TC periphery have different asymmetric features and high wind occurrence frequencies. The strong wind occurrence frequency is the highest when TC centers are located at the island, followed by that when the TC centers are located to the south of the island, and the occurrence frequency is the lowest when the TC centers are located to the north of the island. (3) Radiuses of the maximum wind (RMW) for TCs around Hainan are within the range of 9-185 km and the averaged value is 58.3 km. On the average, the RMWs of TCs located at the island (to the southwest of the island) are the biggest (smallest). (4) The maximum wind speeds near the TC centers sharply decrease from the ocean to the land for all TCs. And high wind speed regions are located at oceanic areas to the west and east of Leizhou Peninsula. (5) The 34-kts wind radiuses on the eastern side of the TCs are larger than that on the western side. And the stronger the TC is, the larger and more symmetry its specific wind radius will be. (6) Different regions have different degrees of wind circle deformation. On average, when the TC is located to the southwest (southeast) of the island, its wind circle experiences the largest (least) deformation.