摘要
以我国西南地区为例,在用加权降水量(W_(AP))改进标准化降水指数的基础上,对综合气象干旱指数(I_C)进行了修正,定义为I_(CW)。通过对比指数修正前后在干旱频率、年干旱强度和干旱发展过程中的不连续加重、以及与同期土壤湿度相关性的差异,分析了I_(CW)在修正后的改进效果及在西南地区的适用性。结果表明:修正前后的综合气象干旱指数在多年干旱频率和年干旱强度两方面没有显著差异,但I_(CW)减少了干旱发展过程中的不连续加重现象,且与同期土壤湿度有更好的相关性,即I_(CW)比I_C更加接近实际干旱的演变规律,I_(CW)比I_C更适合在西南地区实时干旱监测业务中使用。然而,由于该研究未对I_C中的相对湿润度指数进行修正,而相对湿润度指数的突变同样可以导致不连续加重的出现,因此,I_(CW)只是在一定程度上减少了不连续加重的影响。
The meteorological drought composite index（JC） is recommended as an effective operational drought monitoring index from National Standard and has been applied by National Climate Center to monitor drought conditions across the whole country in recent years.However,uncontinurous enhancement of drought is frequently observed in the development of drought process at many stations,where uncontinurous enhancement of drought means that daily change is greater than or equal to one drought degree（—0.6） and the IC value is equal to or less than 0.6 a day before.In order to optimize IC,modified standard precipitation index（Z（65）） by weighted average precipitation（W（AP）） is introduced.Due to different weighted coefficients of daily precipitation,modified IC（I（Cw）） can decrease uncontinurous enhancement of drought to the most extent.Taking Southwest China as an example,daily IC and I（CW）（modified IC） from 1 January 1961 to 10 May 2010 is calculated,and the differences between IC and I（CW） in frequency of every drought degree and monthly variability of drought frequency are analyzed.Since formula and value range of I（CW） are both similar to IC,the same drought degree is adopted.It indicates that there is no significant difference between I（CW） and IC in frequency of drought.Moreover,the annual intensity of drought from 1961 to 2009 is also analyzed.The results indicate I（CW） is also similar to IC very much and there is no significant trend of annual intensity.Furthermore,as stable index of drought,uncontinurous enhancement of drought of IC and I（CW） are counted.It shows that I（CW） has less uncontinurous enhancement of drought than IC at all four stations, so I（CW） has improved the stability of drought according to different weighted coefficients of daily precipitation. Take soil moisture observed on 8,18 and 28 as representative,the correlation between IC,I（CW） and soil moisture is analyzed from January 1993 to May 2010.The results show that I（CW） has greater correlation coefficients with soil moisture of 10 cm at all stations than IC,and I（CW） has greater correlation coefficients with soil moisture of 20 cm at three stations than IC,showing that I（CW） is more consistent with soil moisture. Above all,the analysis shows that I（CW） is close to the characteristics of actual drought and suitable for daily drought monitoring in Southwest China.However,there is still some uncontinurous enhancement of drought existing in I（CW） due to great uncontinuous change of M（30）.
出处
《应用气象学报》
CSCD
北大核心
2011年第6期698-705,共8页
Journal of Applied Meteorological Science
基金
国家科技支撑计划课题(2007BAC29B02)
公益性行业(气象)科研专项(GYHY200906019)
关键词
综合气象干旱指数I_C
加权降水量W_(AP)
西南地区
meteorological drought composite index（IC）
weighted average precipitation（W_（AP））
Southwest China
