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ABSTRACT Heavy rain events or rainstorms of various scales often occur in Hong Kong from April to September. In extremes cases, they lead to serious landslides and flash floods resulting in loss of life, and damage to property and infrastructure. With climate change, extreme rain events are projected to be more frequent and more intense in this region. A system to gauge and label the severity of rainstorms would be useful for identifying and communicating extreme conditions in warning and disaster prevention operations. In parallel, a better understanding of the characteristics of rainstorms would also be important for impact assessments and engineering design purposes. This paper formulates a practical framework to index the magnitude and severity of rainstorms in Hong Kong. An index termed as the Severity Index combining the magnitude of different rainstorm attributes is devised for quantifying the overall severity of rainstorms. This index is flexible to allow tuning for specific applications. [ABSTRACT FROM AUTHOR]

The impact of urbanization for a summertime rainstorm process in the Yangtze River Delta was investigated based on two 96 member ensembles using the Weather Research and Forecasting (WRF) model. Results show that the increase of precipitation mainly occurs downwind of the city belt in this region. The increase and decrease of precipitation forms two zigzag belts in the precipitation area. The t-test illustrates that the discrepancies of near-surface environment around the city belt, the precipitation downwind of the city belt as well as the atmospheric variables in the lower troposphere over the rain belt, caused by urbanization, is significant in such a short-term rainstorm process. Copyright © 2012 Royal Meteorological Society [ABSTRACT FROM AUTHOR]