Abstract
This study examines trends in the intensity and frequency of short-duration (5 min to 3 h) rainfall extremes in Hong Kong for the period of 1984 to 2010 and the drivers for the trends using gauge observations and gridded reanalysis. Both the intensity and frequency of rainfall extremes exhibit an upward trend, with the slope for the intensity (frequency) trend increasing (decreasing) as duration lengthens from 5 min to 3 h. The upward intensity (frequency) trends appear to be a manifestation of an abrupt change around 1991/1992 (1992/1993) that separates a period of lower and fewer rainfall extremes before from a period of higher and more extremes after. The increase in Hong Kong’s extreme rainfall after the early 1990s is likely caused by a combination of stronger rising motion along Southeast China Coasts and enhanced moisture transport into South China Sea resulting from the strengthening and westward shift of the western Pacific subtropical high associated with anomalous convective activities over the tropical western Indian Ocean and a positive phase circumglobal teleconnection wavetrain.
Highlights
It has been widely recognized that heavy precipitation and the associated flooding events have serious socioeconomical consequences
The upward trend over the 27-year period appears to be a manifestation of an abrupt change near the beginning of 1990s that separates a period of lower and fewer precipitation extremes before, from a period of higher and more extremes after, which suggests that the use of linear trend analysis may not be appropriate
The increases in the intensity and frequency of extreme precipitation in Hong Kong after the early 1990s is linked, through composite analyses, to strengthening and westward shift of the western Pacific subtropical high and the associated anticyclonic motion that enhances the transport of moistureladen air as well as rising motion over Hong Kong – the two ingredients for strong convective activities responsible for extreme precipitation
Summary
It has been widely recognized that heavy precipitation and the associated flooding events have serious socioeconomical consequences. The current study focuses on trends in short-duration (≤3 h) extreme rainfall events in Hong Kong. Understanding the trends and interannual variability of short-duration extreme rainfall events in Hong Kong is becoming increasingly important in the context of global warming and local/regional atmospheric circulation change noted above as potential drivers. The current study will examine trends in shortduration (from 5 min to 3 h) rainfall extremes in Hong Kong with a focus on their relationship to large-scale circulations. We examine the trends and interannual variability of the extreme precipitation in Hong Kong in the context of largescale atmospheric circulation and sea surface temperature (SST) anomalies. Mann-Kendall (MK) test (Mann, 1945) is utilized to detect significant trend and abrupt change point in the time series
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