基于Mann-Kendall检验和信息熵的成都市1980—2016年降水时空变化

Spatio-temporal changes of precipitation in Chengdu from 1980 to 2016 based on Mann-Kendall test and information entropy

为探究成都市降水时空变化特点,以1980—2016年该市14个气象站点的逐日降水资料为基础,运用Mann-Kendall法研究降水量动态变化,并应用信息熵理论定量分析降水量在年季尺度上的不确定性。结果表明:1)近36年来成都市年均降水量倾向斜率为-2.049 mm/a,季节性降水量除了秋季呈增加趋势,其他呈减少趋势,且均不显著;同时,在0.05水平上年季降水未发生突变。2)成都市年季降水量增加地区集中于中部双流和东部简阳地区,其他大部分地区降水量呈减少趋势。3)降水量信息熵在不同时间尺度表现为全年>夏季>春、秋季>冬季,在空间上呈自西向东呈减小趋势,综合时空维度来看,降水量越丰富的时空域,其稳定性好、不确定性弱。该研究结果有利于加深理解气候变化背景下区域降水模式变化特点。

[Background]According to studies from the International Intergovernmental Panel on Climate Change(IPCC),the global climate has undergone profound changes during the past ten decades,so has the process mechanism and spatio-temporal distribution pattern of precipitation in recent years.Precipitation plays a crucial role in the water cycle,and energy flow among the atmosphere,vegetation,soil,and other systems,resulting in remarkable environmental disturbances.Chengdu city is located in Sichuan Basin of southwestern China,characterized by the subtropical humid monsoon.Studying the characteristics of precipitation in Chengdu city may provide a significant scientific basis and theoretical support for management of water resources and warning of meteorological disaster here.[Methods]Based on the daily precipitation data of 14 meteorological stations in Chengdu city from 1980 to 2016,the one-dimensional trend of precipitation in this area was studied using simple regression analysis.The abrupt variability of precipitation in time series was detected by the Mann-Kendall method,and the uncertainty and stability of the precipitation were detected by information entropy.On this basis,the visual expression of information entropy distribution regarding regional precipitation was analyzed through the technology of GIS(geographic information system).[Results]1)The chronological changes of precipitation from 1980 to 2016 present variability,with the highest value of precipitation in 2013 at 1 274.77 mm and the lowest in 1997 at 768.6 mm.The average annual precipitation over the Chengdu city is 950.10 mm,showing a trend of gradual decrease with a tendency of-2.049 mm/a.The changing tendency of seasonal precipitation is less obvious.No significant decrease of precipitation(P>0.05)is found in spring,summer,autumn and winter,and neither significant increase in autumn.2)Chengdu city has much uneven rainfall distribution.The average precipitation decreases from the east to the west,with the center located in hilly regions of the eastern hilly region and the lowest in the northern side of the western foothills region.The uncertainty of precipitation varies with time units.3)The information entropy reaches the highest for annual precipitation,followed by summer precipitation,spring and autumn precipitation,and monthly precipitation in order.It indicates that the summer rainfall tends to be as rich and steady as ever,and the precipitation in autumn and spring will become increasingly changeable and difficult to be forecasted accurately and timely.[Conclusions]In recent decades,the precipitation in Chengdu city has exhibited certain temporal and spatial variation.The changing tendency and uncertainty of precipitation in Chengdu city has a close correlation with regional and global climate change.Nevertheless,the specific and detailed process mechanism remains unclear.It is found in this study that the more the precipitation is,the smaller the information entropy and the more uncertainty the precipitation is.