Wednesday, 28 September 2011: 11:45 AM
Monongahela Room (William Penn Hotel)
Hong Kong is small in area but complex in topography with the highest mountain top close to 1 km. From the annual mean rainfall analysis of Hong Kong, it is obvious that the local rainfall maxima are associated with the terrain peaks. When tropical cyclones approach the south China coast, different wind regimes will be experienced by Hong Kong, resulting in various degree of orographic rainfall enhancement in individual locations in Hong Kong.
In this study, radar reflectivity climatology over Hong Kong will be computed for tropical cyclone cases over a time period of 10 years. The results will be stratified according to wind regimes and compared with the corresponding rainfall analyses. The orographic enhancement factor will be computed at each point of the rainfall analysis grid to construct an orographic enhancement map.
The Hong Kong Observatory operates a rainfall nowcasting system known as SWIRLS for the Pearl River Delta region based on the extrapolation of radar reflectivity. Case studies will be conducted to examine how the orographic enhancement map could help improve rainfall nowcast under tropical cyclone situations.
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