SIMULATION OF TROPICAL CYCLONE 201610 (LIONROCK) AND ITS REMOTE EFFECT ON HEAVY RAINFALL IN HOKKAIDO

摘要

When tropical cyclone (TC) 201610, namely Lionrock, was moving over the western North Pacificrnfrom southeast of Honshu to cut across the Tohoku region during 29-30 August 2016, continuous and intensernrainfall occurred in mid- to southeastern Hokkaido, far from the TC center. The Weather Researchrnand Forecast (WRF) model is used to investigate the possible remote effect of TC Lionrock on this heavyrnrain in Hokkaido. The National Center for Environmental Prediction (NCEP) global final (FNL) analysisrnis used to provide both the initial and lateral boundary conditions for the model. Three numerical experimentsrnare performed. In the control experiment (CTL), the original FNL is used. In the no-TC experimentrn(NoTC), the vortex associated with TC Lionrock in the FNL is removed such that the TC signal does notrnappear at the initial time. In the no-topography experiment (noTopo), the terrain height over Hokkaido setrnto 1 m if it is higher than 1 m. As verified against observations, the CTL and noTopo experiments capturernreasonably well the TC track. The CTL experiment also reproduces relatively well the spatial distributionrnand temporal evolution of rainfall, whereas the remote rainfall in Hokkaido is largely suppressed in thernnoTC experiment, suggesting a significant far-reaching effect of TC Lionrock. The combined effect ofrnLionrock and the stationary low-pressure system located over the Sea of Japan enhances the moisturerntransport towards Hokkaido through their outer circulation. Particularly, only very small amount of rainfallrnis observed in Hokkaido in the noTopo experiment, indicating that the orographic forcing of thernsoutheastern mountains in Hokkaido plays the most critical role in this extreme rainfall event.