东北地区夏季干旱的年际—年代际变化特征

利用国家气候中心提供的1951—2012年160个标准站的逐月降水和温度资料,计算了表征东北地区干旱的SPEI指数,并对该指数进行EMSD分解,研究了东北地区干旱的年际—年代际变化特征。结果表明,东北地区夏季干旱年际—年代际变化特征明显,年际变化中具有显著的准2 a、准5 a和准7 a振荡周期;年代际变化中则具有显著的准17 a和22 a振荡周期。进一步分析发现,1975—1984年和1994—2008年为相对干旱阶段,其中1994—2008年旱情比较严重,1953—1975年、1984—1994年以及2009—2012年为相对湿润阶段。Mann-Kendal检验结果表明,东北地区夏季旱涝突变发生在1975年和1994年。

Interannual and interdecadal variations of drought in Northeast China

Based on monthly data of precipitation and air temperature at 160 stations for the period 1951-2012 provided by the National Climate Center of China,the Standardized Precipitation Evapotranspiration Index (SPEI),which characterizes drought,was calculated.Then,the Extreme-Point Symmetric Mode Decomposition (ESMD) of this index was performed to investigate the interannual and interdecadal variations of summer drought in Northeast China.The results showed that summer drought in Northeast China during the study period had distinct characteristics of interannual and interdecadal variations.Significant quasi-biennial,5-yr and 7-yr oscillations occurred in the interannual variations of the SPEI in Northeast China,while quasi-17-yr and 22-yr periods occurred in the interdecadal variations.Further investigations showed that two phases (1975-84 and 1994-2008) were relatively dry,with severe drought having occurred during the latter period (1994-2008).Meanwhile,three phases (1953-1975,1984-1994 and 2009-2012) were relatively wet.Based on the Mann-Kendal test,1975 and 1994 were found to be the change-points of the drought and flood trends for the period 1951-2012.