Using basic daily data of 124 weather stations from 1961 ～ 2007, based on Penman- Monteith method,reference evapotranspiration (RE) and HI are calculated as well as theirs trends and changes of borderline in the wet and dry climate zone are studied. The results show that RE ranges from 500 ～ 1 000 mm and is distributed with large value in the southwestern part and small value in the northeastern part of Northeast China. Annual RE which is decreasing especially from 1960s ～ 1990s and increasing significantly after 2000, demonstrates uptrend in 1/3 zone and downtrend in 2/3 zone in terms of spatial distribution. Humid climatic region where HI is larger than 1.0 is basically consistent with where precipitation is greater than 700 mm. The area of region where HI is smaller than 0.5 is larger than where precipitation is less than 400 mm. The coefficient of variation of HI with range from 25％ ～ 36％ is larger in semi-arid climatic region and is smaller in semi-humid and humid climatic region. With decreasing in the mass HI, semi-arid, semi-humid and the great mass humid climatic regions where positive amplitude of variation of climate tendency of HI is larger than the negative are running dry. The boundary between semi-arid/semi-humid and humid/semi-humid runns from northeast to southwest swings wildly and shows a trend of monolithic translation. At the basic line of 1960s' boundary, the 1980s boundary move westward and the boundary after 2000 move evidenfiy southeastward, which leads to semi-arid region expanding and humid region contracting, in tum, Northeast China is drying gradually and drying areas are enlarging.%利用1961～2007年东北地区124个气象站的温度、降水、风、水汽压、日照等气候资料,采用Penman-Monteith-模型计算参考蒸散量,进一步计算了湿润指数,分析了参考蒸散量和湿润指数的变化趋势及干湿界线的变化情况.结果表明:湿润指数总体呈下降的趋势,变干趋势发生在半干旱半湿润气候区及湿润气候区的大部分地区,湿润指数倾向率负变化幅度大于正变化幅度.湿润指数>1.0的湿润气候区和降水量大于700mm的区域分布基本一致,湿润指数小于0.5的区域大于降水量小于400 mm的区域,湿润指数在半干旱气候区变异系数较大,为25%～36%,半湿润和湿润气候区的变异系数较小;标准差的分布与变异系数有相反的趋势.半干旱-半湿润和湿润-半湿润分界线倾向于东北西南走向,但各年代界线摆动幅度较大,出现整体移动趋势.以1960年代界线为变化基准线,1980年代向西移,2001～2007年代的变化幅度最大,向东南移动明显,半干旱区扩大,湿润区缩小,东北地区有逐渐变干的趋势,进一步说明气候变干的进程加快,干旱范围扩大,程度加强.
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