Based on monthly temperature and precipitation data at northern piedmont of middle Tianshan mountain from 1981-2010,relative moisture index was determined through calculating potential evaporation by using Thornthwaite method.Abrupt change pattern and cycle of relative moisture index was analyzed using Mann-Kendall and Morlet wavelet method.The results showed the precipitation was increased spirally,its spatial distribution is uneven,and temperature showed significant increasing tendency.Under context of global warming,potential evapotranspiration showed spiral ascending trend with significant different spatial distribution (P ＜ 0.01).The potential evapotranspiration change pattern is same in different areas,basically they alternated in same orientation,increasing or decreasing in parallel.Relative moisture index decreased with negative trend from south to north,in range of-0.88 ～ 1.10.After entering 21st century,it showed an obvious climatic aridification tendency and autumn has fastest aridification rate.However it did not show significant abrupt change time zone.Different areas showed discrepancy in oscillatory cycle.3 ～ 6 years had better consistency in oscillatory cycle.At same time,7 ～ 8 years showed obvious low-frequency oscillatory cycle.%利用中天山北坡乌昌地区1981-2010年的逐月降水、气温资料,通过Thornthwaite方法计算潜在蒸数量确定气候相对湿润指数,并分析其时空变化特征；同时应用小波分析及Mann-Kendall法,对相对湿润指数进行突变和周期分析,结果表明:降水量呈波动的增加过程,空间分布不均,气温增暖趋势明显；在气候变暖的背景下,潜在蒸散量呈波动上升趋势,空间上分布差异显著(P＜0.01),各区变化趋势较一致,基本上保持同增同减的过程；相对湿润指数在-0.88 ～ 1.10间,由南至北递减,在时间序列上均呈弱的负趋势.进入21世纪,气候干旱化态势显著,秋季气候干旱化速率快于其它季节,但未出现明显的突变时间区域；各区振荡周期存在差异,但3 a和6 a的周期振荡一致性较好,同时不同时段内7～8a的低频振荡周期表现得也较为显著.
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