Spatio-temporal patterns of extreme precipitation with different durations in the Pearl River Basin

Abstract

[Objective] Under the context of global warming, spatio-temperal pattern of extreme heavy precipitation in the Pearl River Basin have been changing and posesgreat challenges to flood prevention and disaster mitigation. [Methods] Basd on the hourly precipitation data of 125 meteorological stations in the Pearl River Basin from 1979 to 2018, the percentile threshold method is used to define the extreme heavy precipitation events. The extreme precipitation with different durations(1~6 h short duration event, 7~12 h medium duration event, and >12 h long duration event) is identified by fuzzy identification method, and seven rainfall type is considered for classification: single-peaked extreme Ⅰ—Ⅲ means the pre-centralized, the post-centralized, and the mid-centralized type, respectively; Ⅳ is the evenly distributed precipitation; double-peaked extreme Ⅴ—Ⅶ means, with the two peaks of rainfall being located in the beginning and the ending of event, the beginning and the middle of event, and the middle and the ending of the event, respectively. Identified. Then, changes of the rainfall duration and the rainfall type are analyzed in the Pearl River Basin by applying both the linear and non-linear trend analysis method. [Results] (1) The short-, medium-, and long-duration rainfall accounts for 65%, 26%, and 9% of the total extreme precipitation in the Pearl River Basin, respectively. From 1979 to 2018,extreme precipitation with all durations has shown increasing trends, with significant risingtrend observed for short-duration extremes.(2) Short-duration extreme precipitation across the basin falls primarily to Type Ⅰ. For medium-duration extreme precipitation, Type Ⅱ dominates in the Beijiang Basin, while Type Ⅲ prevails in remaining regions. For long-duration extreme precipitation, Types Ⅰ and Ⅲ are predominant in the central Xijiang Basin, whereas Type Ⅱ is dominant in other regions.(3) Compared to the previous 20 years, short-duration precipitation for 1999—2018 in most of the basin continued to be mainly Type Ⅰ. Medium-duration precipitation showed a shift from Type Ⅲ to Type Ⅱ as the dominant type in most of the Pearl River Delta and the Dongjiang Basin. Long-duration precipitation in eastern basin mostly remained Type Ⅱ or shifted from Type Ⅱ to Type Ⅲ, while in western regions, Type Ⅲ remained predominant or shifted towards Type Ⅱ as the main type. [Conclusion] Frequency of the short-duration extreme precipitation is the highest in the Pearl River Basin, and primarily falls to the pre-centralized type has not shown obvious change in for the last 40 years. Distribution pattern of the medium-and the long-duration extreme precipitation shows clear regional differences with the mid-centralized type dominant in the western region while the post-centralized prevails in the eastern region. In the eastern part of the basin, the dominant rainfall pattern mostly remains stable or shifts from the mid-centralized type to the post-centralized, whereas in the western part, rainfall pattern either remains unchanged or shifts from the post-centralized type to the mid-centralized. For adapting flood prevention and disaster mitigation, the specific rainfall type and rainfall duration in the basin, particularly that of the long-duration events in eastern part needs to be considered fully.

Keywords

extreme precipitation / rainfall duration / percentile threshold method / Mann-Kendall trend analysis / rainfall type / Pearl River Basin / spatiotemporal distribution / climate change