环渤海地区云量的时空分布特征

Spatial and temporal distribution of cloud covers in the Bohai Sea region

利用环渤海地区69个观测站点2001年6月-2016年12月8次/d的云观测资料,欧洲中期数值天气预报中心ERA-Interim的垂直速度和比湿数据,初步分析了该地区云量的时空分布特征及成因.结果表明,环渤海地区总云量年平均和秋冬季呈南多北少、西多东少的分布特征,春季分布相对均匀,夏季从东南向西北递减;低云量年平均和各季节的空间分布大体相同,其中对流云量北部山区多于南部平原地区,非对流云量从东南沿海向西北内陆递减,北部低云以对流云为主,南部以非对流云为主.总云量的空间分布与上升运动和水汽的空间分布呈正相关;对流云量的空间分布与大尺度下沉运动呈正相关,与水汽呈负相关;非对流云量的空间分布在秋冬季只与水汽呈正相关,在春夏季只与大范围上升运动呈正相关.两个代表站围场站和莒县站的总云量、围场站的对流云量以及莒县站的非对流云量年变化均比较显著,夏季最多,春秋季次之,冬季最少,主要是由垂直上升运动和水汽的年变化引起的.两站总云量全年各季日变化均不明显,对流云量和非对流云量在夏季表现出明显的日变化特征,对流云量在08:00最少,午后对流活动发展,云量增加,至14:00达到峰值;非对流云量夏季峰值出现在05:00,在14:00达到谷值.

The cloud observation data of 69 weather observation sites in the Bohai Sea region from June2001 to December 2016, and the European centre for medium-range weather forecasts ERA-Interim vertical velocity and specific humidity datasets were used to analyze the spatial and temporal variation charac-teristics and causes of cloud cover in this region. The results showed that, there was more annual average,autumn and winter total cloud cover in the south of the Bohai Sea region than in the north, and more in the west than in the east. The total cloud cover was relatively evenly distributed in spring, and decreased from southeast to northwest in summer. The annual average and the seasonal low cloud cover distributions were roughly the same. The convective cloud cover in the northern mountainous area was more than that in the southern plain area, decreasing from the southeastern coast to inland northwest. The low clouds were dominated by convective ones in the north and dominated by non-convective ones in the south. The spatial distribution of the total cloud cover was positively correlated with the spatial distribution of the ascending movement and water vapor. The spatial distribution of convective cloud cover was positively correlated with a large-scale sinking and negatively correlated with water vapor. The spatial distribution of the non-convective cloud cover was only positively correlated with the water vapor in the autumn and winter, and only with a large-scale ascending movement in the spring and summer. The total cloud cover at the two representative stations, Weichang and Juxian, convective cloud cover in Weichang and non-convective cloud cover in Juxian all underwent significant changes during a year. The cloud cover was the most in summer, the least in winter and more in spring than in autumn, being mainly caused by the annual variations of vertical movement and water vapor. The diurnal variations of total cloud cover at the two stations were not obvious at all seasons. The convective and non-convective cloud cover showed obvious diurnal variations in summer and the convective cloud cover was the least at08:00. The convective activity developed and the cloud increased in the afternoon. The maximum value of cloud cover was reached by 14:00, while that non-convective cloud cover in summer appeared at 05:00, and reached the minimum value at 14:00.