Using conventional mathematical statistics,linear regression and the standard deviation,the quantitative analysis was made on the climate changes in Shenyang.The results showed that the trend of precipitation reduced 155 mm,which was made the greatest contribution by summer and autumn.It decreased 43 mm on the average after the climate jump.The precipitation variability in spring increased and drought risk in spring increased.The first soaking rain limited the spring planting time.The temperature trend raised 1.3℃,mainly in spring and winter.The frost-free period extended about 13 d.The accumulated temperature trends in crop growing season increased 290℃ and it had an average increase of 178℃ after the climate jump.This trend of climate warming made the end of last frost advanced.Early sowing of crops suitably was possible,which was beneficial for agricultural production.The precipitation decrease,the time delay and instability of the first soaking rain were unfavorable for crop growth and seeding.And they became the factors that constrained the normal growth and stabile yield raise of crops.
By using the mathematical statistics and classification,the artificial precipitation enhancement cases in Shenyang area were analyzed.The results showed that the precipitation enhancement weather systems mainly included the northeast cold vortex,high-altitude trough,North China low-pressure,high-pressure rear and cold front cloud system.The appropriate height of precipitation enhancement was about 3 000-6 000 m in the middle and upper part of the cloud layer.The timing of precipitation enhancement should be in the radar's monitoring.The systems moved slowly or maintained stably in the developing or mature stages.The aircraft rainfall enhancement should be used in the stable and deep cloud layers.The rocket and antiaircraft gun rainfall enhancement should be used in the unstable move.
