Abstract: Urumqi area is an important political,economic and cultural center in the Xinjiang Uygur Autonomous Region and northwest China,it is also an inland area threaten by drought.In order to better understand the characteristics of meteorological drought in Urumqi area in summer and study its causes,historical precipitation data from 5 stations in Urumqi area from 1961 to 2015 were utilized,and the statistical result shows that the accumulated precipitation in summer kept changing in the range between 100 mm to 250 mm. Then,Z index was calculated to show the variation characteristics of meteorological drought,and an abrupt change point in mid 1980s and a periodicity change of about 12 years were found by using Mann-Kendall test and Morlet wavelet analysis.Based on this,using NCEP/NCAR re-analysis data and JRA sea surface temperature (SST) data,the causes of drought in summer was studied by comparing the anomalies of relevant meteorological variable fields in drought years and flood years. It is found that water vapor can pass over the Qinghai Tibet Plateau from south to the north at 80~90°E and affect Xinjiang area when the east wind at low latitude West Pacific is strong,otherwise there will be less precipitable water in the northern part of Tianshan Mountains in Xinjiang including Urumqi area. It is also found that the anomalies of vertical zonal circulation of equator caused by SST anomalies in equatorial eastern Pacific is the possible cause of these differences.In addition,the relationship between meteorological drought and 74 atmospheric circulation index in summer in Urumqi is also discussed,and 10 indexes in early season show significant correlations with the drought variation in Urumqi.These results can help to improve the climate forecast and support the weather modification,drought resistance and disaster reduction work.

Key words: Urumqi, precipitation, meteorological drought, variation characteristics, cause analysis