Characteristics and Prediction Model of Summer Drought in Qinghai Province

In this paper,the principle and change tendency of summer drought are studied with the data such as surface observations in Qinghai Province(except for Qaidam Basin),74 circulation features and reseau data at 500 hPa altitude field of Northern Hemisphere.The results indicated that: 1) there were 15 drought events in the summer of Qinghai Province during 1961-2008,with the probability of 31.3% per years.The probability of moderate drought is larger than that of severe drought and extra-severe drought.The probability of drought is larger in eastern agricultural area than that in other areas.2) In typical summer drought years,anomaly at 500 hPa altitude upon Eurasian mid-high latitude is positive,with weak polar vortex;in non-dry years,over Mongolia to the Tibetan Plateau there is negative anomaly,with stronger polar vortex towards the eastern hemisphere,and an active India-Burma trough.3) The western Atlantic in summer and Eurasian zonal circulation index weak last autumn in April Western Pacific Partial August the strong side of the Qinghai-Tibet Plateau surface heating field intensity anomalies index prone to drought in summer;Conversely,West Atlantic type in summer,Eurasian zonal circulation index last autumn on the strong side,the West Pacific-type weak in April,August,Qinghai-Tibet Plateau surface heating field intensity anomaly index weaker,less drought in summer.4) Back substitution of the simulation equation in 1961-2008 indicates that the accuracy is 83.3%(42/48).Severe drought events in 1977,2000 and 2002 can be seen in the prediction.The prediction result for 2009-2010 is close to the truth,showing the trend prediction being credible.