Changes in Characteristics of Late-Summer Precipitation over Eastern China in the Past 40 Years Revealed by Hourly Precipitation Data

Abstract

Using hourly station rain gauge data during 1966?2005, the authors studied changes in the characteristics of the late-summer (July?August) rainfall, which has exhibited a so-called southern flooding and northern drought (SFND) pattern over eastern China in recent decades. Although the rainfall amount and frequency have significantly increased (decreased) in the mid?lower reaches of the Yangtze River valley (North China) during this period, the rainfall intensity has decreased (increased). This finding differs from previous results based on daily data, which showed that the rainfall intensity has increased in the mid?lower reaches of the Yangtze River valley. In this region, the mean rainfall hours on rainy days have increased because of the prolonged rainfall duration, which has led to an increased daily rainfall amount and to a decreased hourly rainfall intensity. Results also show that the SFND pattern is mostly attributed to changes in precipitation with moderate and low intensity (≤10 mm h?1), which contributes 65% (96%) of rainfall amount to the ?flooding? (?drought?) in the mid?lower reaches of the Yangtze River valley. Neither frequency nor amount of strong intensity (>20 mm h?1) rainfall exhibits the SFND pattern.