Periodicity of drought is decreasing in Gansu Province, China

摘要

Five hundred years of drought data were analyzed for Gansu Province in China. Using wavelet transform on a large scale, we identified that droughts occur in a periodic way. The lasting time of both aridity and humidity statuses are reducing, namely the periodicities are decreasing. Over the past five hundred years, the lasting time of drought shortened from 121 years to 74 years in recent centuries, and the lasting time of humidity-state shortened to from 84 years to 12 years. A smaller periodicity (∼25 years) is also decaying at a rate of two years per 100 years. The results indicate that drought disasters will afflict Gansu more frequently in the future.