The sand－dust storm weather occurred on April 24，2010 in the middle of Hexi Corridor was studied．The results show that the strong cold air from the northwest route resulted in this heavy dust storm，it occurred during the process of 500 hPa circulation situation transition from the latitudinal to longitudinal direction．The continual temperature rising provided the favorable thermal condition for sandstorm．The upper and lower level jet stream provided the dynamical condition for it．The exist of dry－warmer area was an omen for its occurrence and it provided abundant sands．The unstable atmospheric structure with warm lower and cold upper was good for the momentum transmitting downwards of the strong wind in upper air．The daily forecast indexes and equations under the different weather conditions were summarized based on the meteorological data from 1969 to 2004 in the middle of Hexi Corridor and the numerical forecast products from 1986 to 2004．The now－forecast indexes were modified and complemented，and it played a well role in the forecasting work of dust weather．

Based on daily precipitation data from five stations in Wuwei(located in east of Hexi Corridor)from 1960 to 2009，the spatial and temporal distribution of precipitation over 10 mm(daily precipitation≥10 mm)was analyzed systematically in this paper．The results show that precipitation over 10 mm was more obviously in south part than that in north of east Hexi Corridor．Annual variation of precipitation days over 10 mm was not consistent in each region，and it presented increasing trend in Tianzhu，Yongchang and Minqin，but decreasing trend in Liangzhou and Gulang．The rainfall(precipitation over 10 mm)weather occurred maily in April to October，especially in July and August．Precipitation over 25 mm only occurred in May to September，and the annual precipitation correlated with occurrence times of precipitation over 25 mm．The circulation situations which resulted in precipitation over 10 mm in east Hexi Corridor were Xinjiang cold trough moving to east and south，and southwest air current，and the abundant water vapor condition，the intense lifting movement and the unstable energy were essential conditions．Based on data of ECMWF numerical forecast grid field，the factors were initially selected with Press criterion and selected accurately with stepwise regression forecast method，the forecast equations for precipitation over 10 mm were established with optimal subset regression．The most superior significance forecast equations of precipitation over 10 mm in each region were determined finally with the CSC double grading criterion．Forecast marginal value and qualitative forecast of precipitation over 10 mm were determined using principle that the fitting and the summary rate were the biggest simultaneously．

Based on FY - 2 infrared images and the reanalysis data for six hours ofNCEP (1°×1°) , the heavy dust storm p rocess occurred on 13 Ap ril 2007 in the middle west part of Hexi corridor is analyzed, particularly the cloud head of the descending jet was tracked and the gravitational instability, conditional symmetric instability and conditional instability are diagnosed in detail. Results show that a high speed descending jet resulted in this heavy dust storm and the jet triggered strong convection in frontal region, and conditional instability occurred in themiddle part of troposphere first, then developed downwards. The release of conditional instability energy at the level of 700 hPa caused rap id development of convective circulation in boundary and brought on this heavy dust storm.

The spatial and temporal characteristics of drought which occurred in 2001 in Zhangye city were analyzed in this paper, an
the severity and the last time of this drought event were compared with those which happened in past years, at the same time, the at-
mosphere circulation, hydrology and ecology drought in 2001 were also analyzed. The results show that 2001 was another arid yea
following 1962, and the severity of the drought was rare in recent 50 years, and it was associated with the unusual atmosphere circu-
lation at the level of 500 hPa, and the current drought condition were presented too. The conclusions were significant to the aridit monitoring and defending for the west region of Yellow river.