Interaction Between Typhoon and Western Pacific Subtropical Anticyclone: Data Analyses and Numerical Experiments

Three kinds of typhoons with distinct tracks are sorted based on a set of typhoon data from 1958 to 1998. The results of composite analyses con rm that different typhoon tracks correspond to different patterns of the subtropical anticyclone over the western Pacific (SAWP). When the tracks are westward, the SAWP is strong, with a zonal form, and stretches westward; when the tracks are recurving, the main body of the SAWP shifts eastward and breaks near 160°E; and when the tracks are northward, the SAWP is located far east of its normal position. Based on the above result, two different initial fields are con gured, one has a zonal and strong SAWP, and the other has a meridional and weak SAWP. By using the GOALS R42L9 climate model, a temperature disturbance is added into these two different initial fields to force the formation of a typhoon. Westward and northward tracked typhoons are well simulated, thus verifying that different patterns of the SAWP have different effects on typhoon tracks. Results also show that typhoons can induce barotropic Rossby waves propagating to the mid and high latitudes. Under different background zonal flows, the wave trains triggered by the typhoons of westward and northward tracks are also different, and their effects on the mid and high latitude circulations and the SAWP are different. Compared to a northward tracked typhoon, a westward tracked typhoon is able to induce positive geopotential height anomaly to its north and northwest, resulting in the SAWP strengthening and developing westward.