Historic climate variability of wetness in East China (960–1992): a wavelet analysis

Abstract

Temporal and spatial climate variability in East China is analysed for the last 1033 years (AD 960–1992) based on historic annual grades of wetness for six regions in East China. This data set is subjected to a ‘Mexican hat’ wavelet transform for displaying variations of different frequencies at particular time points, persistent anomalies, and abrupt changes between them. The following results are noted: the persistent dry stage 1120–1220 and wet stage 1280–1390 in the coastal regions are the outstanding features during the last 1033 years. For all regions an almost synchronous change occurs around 1890 from a weaker wet phase to a weaker dry phase; climatic variations on longer time-scales cover larger areas. On shorter time-scales, synchronous fluctuations are observed in fewer years than longer time-scale variability. © 1997 the Royal Meteorological Society.