青藏高原OLR场的气候特征

青藏高原OLR明显偏低。季节变化特点是1月到5月不断增值，3－5月增值迅速。5－8月高原北部继续增值，但南部云量增多，出现了低值区。低值区5月份在喜马拉雅山南侧，然后自东南向西北扩展，越过喜马拉雅山，7月低值轴线到达31°N附件；8月开始自西北向东南撒；9月退到喜马拉雅山南侧；10月开始下降，西北部下降迅速，东南部下降缓慢。年变化曲线特点是：高原北部为单峰型，最高值出现在8月；南部为双峰型，高值分别出现在5月和10月，低值出现在7月。

THE CLIMATIC CHARACTERISTICS OF OLR FIELD OVER QINGHAI-XIZANG PLATEAU

The seasonal changing characteristics of OLR field over Qinghai-Xizang Plateau increases unceasingly from Janurary to May, and increases rapidly in March to May .It increases constantly in the Northern Plateau from May to August. Because of influences of the Indian monsoon in the Southern Plateau, the convection activity becomes stronger and a low-value zone of the OLR field appears. The low-value zone of May is in the southeast, and then spreads toward the northwest from the southeast crossing the Himalayas, and reaches the proximity of the northern latitude 31 in July. The low-value zone begins to withdraw to the southeast from the northwest in August, and to the southern side of the Himalayas in September. Because of the influences of the northwest currents at the outset of October, the OLR field value begins to drop from the northwest Plateau quickly and the southeast slowly. The characteristics of the annual variation curve are: it is a single-front type in the northern Plateau for the OLR with the highest value in August. It is a double-front type in the southern Plateau with the highest value in May and October respectively. It reaches the lowest-value in July.