|dc.description.abstract||Although there have been many observational and modeling studies of tropical cyclones, understanding of the budgets of clouds and precipitation and the interaction between typhoon and terrain are still limited. In this study, the fifth-generation Pennsylvania State University-National Center for Atmospheric Research (PSU-UCAR) Mesoscale Model (MM5) is used to simulate Typhoon Nari, and high-resolution (2-km horizontal grid size and 2-min data interval) model outputs are used to examine water budgets, then compared between typhoon on the ocean and in land . All budget terms are derived directly from the model. The typhoon circulation is separated by two distinct components, the inner core (R=0-50 km) and outer rainband (R=50-150 km) region, respectively.
The typhoon structure has significant differences before and after landfall. Before landfall, the condensation latent heating is distributed at mid-to-high levels within typhoon eyewall; after landfall, the typhoon structure is more asymmetric and has evident titling eyewall induced by Taiwan terrain. The condensational heating rate is distributed at low-to-mid levels. The hourly-averaged condensational warming within the eyewall is one time increased and is peaked at lower altitude, compared to those over ocean.
In the budget result, when the typhoon over the ocean, the inward-to-eyewall horizontal vapor transport within PBL is about 23.5% of total condensation and the PBL source term is only about 1.3% of total condensation. The ocean source of water vapor in the inner core region is a small portion of horizontal transport, consistent with previous finding. After landfall, the Taiwan terrain effect enhanced typhoon secondary circulation. Therefore, it induced strong water vapor convergence and much mass and moist is carried into the outer spiral rainband region. In the cloud and precipitation budget, the ice and guraple transport outward to outer spiral rainband region is increased by terrain which induced Chiyi area 24-h accumulated rainfall exceed to 522.5 mm.
Further, we calculated cloud microphysics precipitation efficiency (CMPE) which is defined as the volume-integral precipitation divided by the volume-integral condensation and deposition, and large scale precipitation efficiency (LSPE) which is defined as the volume-integral precipitation divided by the volume-integral water vapor convergence. CMPE increased from 62% to 70% and LSPE also increased from 30% to 45% compared with before and after landfall. Because of Taiwan terrain enhance typhoon secondary circulation, more water vapor transport inward to inner core region. It makes the cycling rate of precipitation process fast.