Spatial and Temporal Variation in Extreme Precipitation Events in Southwestern China during 1962-2012

Based on daily precipitation data for 90 stations from 1962-2012,extreme precipitation events were defined using the percentile threshold method and analyzed in time and space using the Mann-Kendall rank correlation method and inverse distance weighted interpolation method. The results showed that annual daily maximum precipitation and the extreme precipitation ratio decreased from 103~118mm and 39% ~43% in eastern areas to 25.4~46.7mm and 23% ~25% in western areas. Extreme precipitation,extreme precipitation intensity and annual 5-days maximum precipitation decreased from 508~610mm,55~64mm/d and 158~190mm in southeast areas to 118~ 220mm,17~28mm/d and 53~85mm in northwest areas,respectively. The variation coefficient of annual daily maximum precipitation amount is the largest and up to 39%,followed by that of the extreme precipitation amount, extreme precipitation intensity, annual 5-days maximum precipitation and extreme precipitation ratio;extreme precipitation days is the smallest and only 18%. The variation coefficient of extreme precipitation events was stronger and indicates larger differences in extreme precipitation events in the southwestern region. Among extreme precipitation events from 1962-2012,sites with an upward trend for annual daily maximum precipitation amount,extreme precipitation intensity and ratio accounted for 60%,64% and 61% and the significant upward trend reached 12%,10% and 13%,respectively. Sites with an extreme downward trend and significant downward trend for extreme precipitation days accounted for 52% and 4% respectively. On the whole,extreme precipitation events followed an upward trend overall, but not significantly,on account of ocean temperature anomalies and the complex geographical environment.