温江站夏季大气边界层垂直结构特征

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。

The complete structure characteristics of boundary layer in summer at Wenjiang

Using the observation data from boundary layer tower and sounding, we analyze the characteristics of boundary layer in summer at Wenjiang. The results indicate that: (1)Every physical quantity at surface has daily variation.SSensible heat and latent heat flux, momentum flux, temperature and wind speed has a peak and valley. The peak appears in the afternoon, and the valley value appears in the early morning. Daily variation of the humidity contrary to the temperature. There are double peak and valley for ground barometer. (2)The ground layer atmosphere vertical profile shows: The temperature increases with the height at sooner or later period of time. The temperature decreases with the height at midday period of time. The value of humidity is large, and gradient of humidity is small near the ground layer. The inverse wet can be observed all the time. Wind speed values increase with height, wind speed gradient decreases with the height.(3) Vertical structure of the boundary layer from Sounding observations shows: Temperature/humidity decreases with height growth, , the differences of temperature/humidity mainly concentrated in the lower atmosphere at all time. The difference of temperature/humidity is more prominent as the more close to the ground. The highest temperature value appear at 14:00,and the lowest temperature value appear at 08:00. The minimum of humidity appear at 14:00,the value of humidity is bigger at 02:00/20:00. The wind speed near ground increase with height ,the difference of wind speed is small at 4 times.(4) There is a good positive correlation between thickness of boundary layer and temperature/shortwave radiation/sensible heat flux. There is a negative correlation between thickness of boundary layer and relative humidity/precipitation.