温江站夏季大气边界层垂直结构特征

The Vertical Structure Characteristics of Boundary Layer in Summer at Wenjiang Station

利用温江观测站边界层塔和探空获取的观测资料,从地表物理量的日变化、边界层的垂直结构及逐日变化这些方面分析该站夏季边界层特征,得到以下结论:(1)地表各物理量都具有明显的日变化特征,呈现一峰一谷的演变状态,其中地表热通量、动量通量、气温以及风速的峰值皆出现在午后,谷值出现在凌晨,湿度与气温日变化是反位相的。(2)近地层低层大气气温在早晚时段,随高度的增加而上升,呈逆温状态;午间时段随高度的增加而下降。9 m以下大气在午后的比湿梯度最大。风速值随着高度的增高而增大,风切变随着高度的增高而减小。(3)探空观测的边界层垂直结构显示:夏季温江站早晚边界层大气层结稳定,而午后表现为典型的混合边界层特征。大气温/湿度差异随高度增长而降低,各个时次温/湿度的差异都主要集中边界层低层,越靠近地面大气温/湿度差异越突出。8:00的温度最低,14:00最高。14:00的大气比湿最小,2:00和20:00较大。近地层风速随高度增长较快,在离地2~300 m左右高度达到一个极值,4个时次的风速差异不大。(4)地表温度、短波辐射、感热通量对边界层的高度和降水都有一定的影响。

Based on the observational data from boundary layer tower and sounding at WenjiangStation,the characteristics of boundary layer in summer from three aspects of daily variation,vertical structure and day-to-day variation were analyzed. The results showed as follows（1）Thephysical quantities in the surface had obvious daily variation,appearinga peak and valley evolutionstate. The peak values of sensible heat flux,momentum flux,temperature and wind speed appearedin the afternoon,and the valley values appeared in the early morning. Humidity variation was out ofphase with temperature.（2）The temperature in the lower surface layer increased along with theincreasing of height in the morning and at night,showing inversion state,but decreased with theincreasing of height in the afternoon. The gradient of moisture was biggest below 9 m in theafternoon. Wind speed increased and wind shear decreased with the increasing of height. （3）Thevertical structure of boundary layer through sounding showed：atmospheric stratification was stablein the morning and at night,but was extremely unstable in the afternoon. The temperature andhumidity decreased with the increasing of height,and the marked differences mainly appeard in thelower surface layer. The closer they approached to the ground,the more remarkable theirdifferences were. The highest temperature appeared at 14： 00 and the lowest value appeared at08： 00. The minimum of humidity appeared at 14： 00,and was bigger at 02： 00/20： 00. The windspeed near the ground increased quickly with the height,and reacheda peak value in the level of200-300 meters. In four times the difference of wind speed was small at 4 times. （4）Surfacetemperature,short radiation and sensible heat flux had a certain influence on the boundary layerheight and precipitation.