Multiscale variability of China’s historical flood/drought index and precipitation teleconnections with ENSO using wavelet analyses

Abstract

Studies of the low-frequency variabilities of key climate variables are often handicapped by the limited length of available instrumental observations. To tackle this, the use of a set of historical flood/drought index (FDI) spanning from AD 1470 to 2000 for 120 sites in China has been made to investigate the multiscale temporal variability of annual precipitation by applying wavelet methods. The analyses reveal oscillating components of the FDI time series from the decadal to multi-decadal, and to the quasi-centennial range, as well as in the interannual range. Furthermore, the relationships of the FDI with the dominant mode of oscillations in the coupled ocean–atmosphere system, i.e., the El Niño-Southern Oscillation (ENSO) index, on a range of time scales have been probed by cross wavelet transform and wavelet coherence methods. Statistically significant coherence between FDI and ENSO index time series has been found for regions in eastern China south of the Yangtze River (inclusive) at the decadal to multi-decadal time scale (10- to 50-yr) after 1750, as well as for north China on the 10- to 30-year range in the eighteenth century. The FDI is less coherent with the ENSO index for other regions of China. The results of the present study may add to our understanding of the connections between long-term changes of annual precipitation and large-scale oscillations in the coupled ocean–atmosphere system, and provide a scientific basis for developing policies to adapt to future changes in water abundance.