摘要
基于地面逐时观测资料,分析了华北夏季旱、涝年各类云的云量变化,并用ERA再分析资料探究其变化原因。结果表明,华北地区雨层云、层积云、层云和积云云量在旱、涝年的变化趋势相反,除高层云外其余各类云在涝年的降水概率大于旱年。华北夏季旱年500 hPa高度距平场呈现纬向型的鞍形场,华北地区和东部海域呈现出"西高东低"的距平环流形势。850 hPa风场在贝加尔湖以南为反气旋性异常中心,西太平洋地区为气旋式距平环流。华北地区受控于脊前的偏北距平气流,不利于暖湿水汽向华北地区输送。高层为散度负距平,低层为散度正距平,不利于云的形成和云产生降水。涝年与之相反。
Using statistics and composite analysis methods,the characteristics of cloudiness over northern China in drought and flood summer are analyzed based on surface observation dataset and the reasons for their variations are also explored based on ERA reanalysis data in this paper. The cloudiness of nimbostratus,stratocumulus,stratus and cumulus decrease in drought years,but increase in flood years. Except for altostratus,the precipitation probabilities for other various cloud types in flood years are larger than those in drought years. 500 h Pa geopotential height anomaly shows a ＂zonal saddle field＂and geopotential height anomaly over northern China is larger than that over eastern sea region in drought years. An anticyclone anomaly center is located in the south of Lake Baikal in 850 h Pa wind field,but the western Pacific region is controlled by cyclonic circulation anomaly. Northern China is dominated by anomaly of northern air stream,which is not conducive to warm and wet water vapor transport to northern China.Negative anomaly of divergence in upper troposphere and positive anomaly in lower troposphere go against the formation of cloud and even precipitation. While in flood years there presents an opposite situation.
出处
《气象与减灾研究》
2015年第2期16-21,共6页
Meteorology and Disaster Reduction Research
基金
财政部/科技部公益类行业专项(编号:201306068)
国家自然科学基金(编号:41475069)
国家留学基金
关键词
华北
夏季
旱涝年
云量
大气环流
north China
summer
drought and flood years
cloud amount
general circulation
