降水极值的非平稳性特征及其重现期研究--以福建省为例?

变化环境下降水序列具有普遍的非平稳性.为深入探究降水极值的非平稳特征及其对极端降水重现期的影响,本文以福建省22个站点为例,针对表征降水序列非平稳特征的2个重要变量均值和方差,利用经验模态分解法(EMD)、Mann-Kendall趋势检验法分析了1960—2012年前汛期、后汛期降水极值序列非平稳特征;运用贡献分析法分析降水极值序列均值和方差变化对非平稳的降水极值确定性趋势的增量贡献;构建非平稳模型,基于均值、方差趋势探讨极端降水的重现期变化特征.结果表明:1)福建省前、后汛期降水极值序列非平稳性较强,前汛期闽西、闽北、闽中方差增加显著,部分站点方差变化对降水极值确定性趋势的增量贡献较大;后汛期全省降水极值均值普遍呈现增加趋势,对降水极值的确定性趋势起主导作用.2)福建省前汛期极端降水趋势增大的站点位于闽北地区,因为降水序列方差的线性增加趋势导致极端降水量显著增加;后汛期极端降水趋势增大的站点位于闽西和闽南2个区域,其中多数站点因为均值的增加趋势导致极端降水量增加,但是增加幅度平缓.3)降水序列方差的改变更加显著地影响了极端降水重现风险,变化环境下极端降水趋势和风险研究需充分考虑降水序列的非平稳性.

Non-stationary characteristics of precipitation extreme and its impact on disaster risk in Fuj ian

Precipitation series normally have non-stationary characteristics under changing environment. To explore in-depth non-stationary characteristics of precipitation extremes and its influence on risk of extreme precipitation,temporal-spatial characteristics of the mean and variance of precipitation extremes series were analyzed by empirical mode decomposition (EMD)and Mann-Kendall test.These non-stationary characteristics were derived from 22 meteorological stations in Fujian Province in pre-and post-flood period from 1960 2012. Contribution analysis was also done to investigate contribution of mean and variance trends to precipitation extreme increments.Temporal characteristic of extreme precipitation risk was explored based on trends of mean and variance in non-stationary model. Precipitation extreme series were found to show significant non-stationary characteristics in both pre-and post-flood season.In the first flood season,variance had a remarkable increase in the west,north and central of Fujian while the trend of variance showed a bigger contribution to trend of precipitation extremes series.In the second flood season,the mean of precipitation extremes series increased widely in Fuj ian,playing a leading role in the increasing trend of precipitation extreme.As a whole, precipitation extreme had a more general and obvious increasing trend.The risk of extreme precipitation in the first flood season was enhanced in northern Fujian,because variance of precipitation extreme series had a liner increasing trend leading to increased extreme precipitation.The risk of extreme precipitation in the second flood season increased in west and south Fuj ian.The increasing trend in mean has led to the increasing trend in extreme precipitation in most stations.But the trend was gentle.Change in variance affected risk of extreme precipitation significantly.It is necessary to take non-stationary characteristics of precipitation series into account in the study of extreme precipitation trend and the risk of extreme precipitation under changing environment.