The microphysical processes of Typhoon Nari (2001) at landfall

In this study, numerical simulations of the landalling Typhoon Nari (2001) are carried out using a quadruply nested-grid MM5 model with the finest grid size of 2 km. The control simulation reproduces reasonably well the kinematic and precipitation features as well as the structural changes of Nari, as verified against satellite, radar, and rain gauge observations. These include the storm track, contraction and sizes of the eye and eyewall, the spiral rainbands, the intensity change, and the rainfall distribution and some local rainfall maxima. Condensational warming occurs in the mid-to-upper levels within the eyewall, and evaporative cooling is dominant in the lower to middle levels in spiral rainbands. Depositional heating mainly appears in mid-to-upper levels of eyewall and spiral rainbands, sublimative cooling occurs in the middle level, and melting cooling is located near and beneath the melting level. After Nari's landfall on Taiwan, condensational warming (evaporative cooling) is enhanced (weakening) over the windward slope; for the ice-phase processes, depositional heating (melting cooling) is further increased (decreased) over the mountainous region. Four sensitivity experiments are conducted to examine the sensitivity of typhoon track and intensity to microphysical processes such as ice-phase process, evaporative cooling, sublimative cooling, and melting cooling. It is found that storm's track is weakly dependent on microphysical processes; storm intensity is more sensitive to the ice-phase microphysical processes, which can result in 15 hPa or 10 m/s difference.