The water budget of Typhoon Nari (2001) at landfall

In this study, water budgets of Typhoon Nari (2001) are conducted using outputs from a quadruply nested-grid MM5 model with high spatial and temporal resolution (2-km horizontal grid size and 2-min data interval). As shown in Yang et al. (2008), the control simulation reproduces reasonably well the track, intensity, kinematics and precipitation features as well as the structural changes of Nari, as verified against satellite, radar, and rain gauge observations. Water budgets of Nari prior to and after landfall on Taiwan are calculated following the method of Braun (2006). While Nari is still over open ocean, condensation occurs mostly within in deep updrafts in the eyewall and also within weak mesoscale updrafts in outer rainbands. Cloud hydrometeors are quickly converted to precipitation particles after they are produced. Precipitation efficiency defined by the ratio of volume-integral precipitation versus total condensation (including deposition) is about 45% over the eyewall. After Nari's landfall on Taiwan, the hourly-averaged condensational warming within the eyewall is increased from 15 K h-1 to 29 K h-1 and is peaked at lower altitude (5 km to 3.5 km), compared to those over ocean. Precipitation efficiency in the eyewall is enhanced to 67 % after landfall, consistent with the increased surface rainfall over terrain. The ice-phase latent heating/cooling processes remain similar profiles after landfall, because the 150-km width of the Central Mountain Range on Taiwan is not wide enough to substantially affect the ice-phase hydrometeors in Nari' s outer rainbands.