Coherent modes in multi‐scale variability of precipitation over the headwater catchments in the Pearl River basin, South China

Abstract

This paper studies the coherent modes of multi-scale variability of precipitation over the headwater catchments in the Pearl River basin in South China. Long-term (1952–2000) daily precipitation data spatially averaged for 16 catchments in the basin are studied. Wavelet transform analysis is performed to capture the fluctuation embedded in the time series at different temporal timescales ranging from 6 days to 8.4 years. The catchment clusters of the coherent modes are delineated using the principal component analysis on the wavelet spectra of precipitation. The results suggest that as much as 98% of the precipitation variability is explained by only two coherent modes: high small-scale mode and high seasonal mode. The results also indicate that a large majority of the catchments (i.e., 15 out of 16) exhibit consistent mode feature on multi-scale variability throughout three sub-periods studied (1952–1968, 1969–1984, and 1985–2000). The underlying effects of the coherent modes on the regional flood and drought tendency are also discussed.