Based on daily meteorological observation data in main apple producing areas of China from 1971 to 2017, the crop coefficients at different growth stages of apple were corrected, firstly. And on this basis the precipitation suitability model at each growth stage of apple was constructed. Then, combined with the geographical distribution of apple in advantageous areas, the threshold of precipitation suitability of apple, and the spatial and temporal distribution characteristics of precipitation suitability at each growth stage of apple were analyzed. Furthermore, the temporal and spatial anomalies were discussed by using empirical orthogonal function (EOF) decomposition method. The results are as follows: (1) The thresholds of precipitation suitability at initial growth stage, vigorous growth stage and later growth stage of apple were 0.30-1.29, 0.63-1.78 and 0.62-2.84, respectively. The areas within the threshold range at each growth stage of apple accounted for 94.8%, 94.7% and 95.9% of main producing areas, respectively. The change trend of precipitation suitability in most regions at three growth stages of apple wasn’t significant from 1971 to 2017. (2) The variance contribution rates of the first eigenvector field of precipitation suitability at initial growth stage and vigorous growth stage of apple were 50.53% and 32.26%, respectively. The eigenvalues were almost positive in the whole region, which indicated that the spatial change of precipitation suitability had good consistency, and the oscillation intensity of precipitation suitability strengthened from northeast and southwest to the middle. The variance contribution rate of the first eigenvector field of precipitation suitability reached 49.51% at later growth period, and the distribution pattern in Liaoning Province and the local part of eastern Hebei Province was opposite to other areas. (3) The second eigenvector field of precipitation suitability appeared an opposite phase distribution pattern in the east and the west at initial growth period of apple, while that were anti-phase distribution pattern in northern and southern parts at vigorous growth period and later growth period of apple. 

By using the reanalysis data of NCEP (1°×1°) , the dry intrusion characteristic of a strong dust storm p rocess occurred in the Hexi Corridor from Ap ril 9 to 10, 2006 was analyzed. The results show that the high potential vorticity, dry air from the upper level of troposphere extended downwards and southwards, which increased the vertical component of the vorticity on the steep iso - entropy p lane and p romoted the rap id development of the low level cyclone, resulted in a low level jet and the intensive convergence in the
boundary layer.