Comparative Analysis Of Multi-time Scales Drought Characteristics Based On Four Drought Indices In Northeast China

The drought develops slowly and lasts for a long time,very easy to form a severe drought with multi-time scales which across months,seasons or even years.To understand the capability of drought description with drought indices at various time scales,has an important significance to assess regional drought and manage risk at multi-time scales.In this paper,Standardized Precipitation Evapotranspiration Index(SPEI),Meteorological Drought Composite Index(CI),K Drought Index(K)and Effective Drought Index(EDI)are calculated corresponding values at various time scales by using daily ground observation data from 90 meteorological stations during 1960-2014,and used to analyze the capability of drought description under various time scales in Northeast China(Heilongjiang,Jilin and Liaoning province),The results are as followed:(1)the distribution analysis presents that precipitation decreased as the spatial variation from southeast to northwest of Northeast China.Variation of precipitation in spring is contrary to that in summer and autumn,which all shows a non-significant trend,and Stations in Winter shows a significant increasing trend except subarea I(the western part of Liaoning)and westward of subarea ?(the eastern part of Liaonig and central and southern parts of Jilin).The potential evaportranspiration in west are higher than east.Subarea I and westward of subarea IV(most of the central part of Heilongjiang)are higher-value region in spring and summer,thereinto,spring shows a significant downward trend apart from subarea V(the northern part of Heilongjiang)and summer shows only in subarea ?.While in autumn and winter,higher-value region moves to subarea I and south of subarea ?,moreover,a significant downward trend is presented in former and an opposite trend is showed in the NE of subarea ?.(2)Correlations between four drought indices are increase with increasing of scale,and the maximum value appears at 12-month time scale with CI,K and at 6-month time scale with EDI.Correlations between SPEI and CI,K are better than EDI at all time scales,in addition,its value in east is higher than west at short-time scales.(3)The description of the dry and wet conditions by SPEI,CI and K in subarea ?,III(the northeast part of Jilin and southeast part of Heilongjiang),V is better than in subarea I,IV at 1-month time scale.In the latter regions,K is suitable for describing the drought in spring and summer(from March to September),but it's easy to show up extreme value in the region which precipitation decreases and evaportranspiration increases significantly such as the autumn and winter(from November to February)with poor precipitation in subarea I.CI is less sensitive to wet period and SPEI describes dry and wet periods reasonably except the intensity.(4)The assessment ability of four drought indices in wet months is better than dry months at multi-time scales,in the latter,SPEI,CI and K is more appropriate for these stations which has abundant precipitation and indistinctive fluctuation.The results of monitoring seasonal drought by four drought indices shows that consistency in summer is better than autumn,and rather than spring and winter.CI and K have similar performance in drought duration especially in the grades of near normal and moderate drought,while evaluating more drier in the wet years of spring and winter.EDI can not only reflects the duration,but also reflects the change caused by sudden increase or decrease of precipitation in a certain period of time.The ability of monitoring spring drought by SPEI is poor in subarea I and ?(Liaoning province).(5)The spatial patterns of K at various time scales are consistent with the subarea based on precipitation.However,there still has a difference in the high load values of the principal components,thereinto,PC-1 is concentrated in subarea I and II,PC-2 is always located in subarea IV,and PC-4 and PC-5 have an obvious difference at 1-month time scale.The correlativity between various time scales is best in neighboring time scales such as 1-month and 3-month.The degree of drought increases or decreases with the increase of scale at 1-month,3-month and 6-month time scale,while turns normal or near normal at 12-month time scale in Northeast China.