Water Budgets of Tropical Cyclones: Three Case Studies

In this study, three tropical cyclones (TCs) that passed through the Taiwan Strait were analyzed; our results show that precipitation is not directly related to the intensity of TCs. From the perspective of water budget, moisture flux convergence was dominant and contributed ～70% of the moisture for TC precipitation over the ocean and almost all over the land, especially inside the TC circulation. Their spatial distributions were also similar. Evaporation contributed ～30% of the moisture for precipitation over the ocean but changed little with the time. Moisture flux convergence can be divided into two parts: wind convergence and moisture advection. Moisture flux convergence was mostly due to wind convergence, which was dominant in the southwestern quadrants of the TCs. Moisture advection was located in the northern area, and becomes relatively important when the TCs approached the land. The moisture flux convergence and its two parts varied during TC movement, with strengthening and contraction of moisture convergence present near landfall. The vertical structure of the three TC cases all indicated that the moisture convergence was mainly confined to the lower atmosphere under 800 hPa and a weak divergence region was present in the middle troposphere around 550 hPa.