Dynamic Response of Surface Layer Turbulence due to Solar Radiation Change

在不同地表条件下，利用太阳辐射测量进行了大气湍流测量。观测系统由三维声速风速仪、热电偶干湿仪、红外湿度计/二氧化碳计和温度廓线系统组成。通过对海面、水田农田和裸露土壤等不同地表条件的测量，发现太阳辐射变化对地表热容的影响最为敏感。海面上的表面边界层对太阳辐射变化的敏感性较低。水田实测表明，感热湍流通量主要受辐射变化的影响，水汽通量和二氧化碳通量不太敏感。在观察地表植被时，我们应该考虑到植物生理学。在距离裸露土壤表面1.28m处观察到8个对数水平的温度波动。发现地表温度对太阳辐射变化有响应，时间常数为2 ~ 2.5 min。空气温度随地表温度变化而变化。较高水平的空气温度比较低水平的响应延迟较小。气温峰值并不总是与地表温度一致，但在地表温度最高之前达到峰值。表面边界层响应的机理如下：表面。温度的变化是由于太阳辐射的变化。增加了温度湍流。因此，感热通量增加，最终转向较高的气温。

Atmospheric turbulence measurements were carried out with solar radiation measurement at various surface conditions. The observation system consists of 3-dimensional sonic anemometer, thermocouple psychrometer, infrared hygrometer/carbon dioxide meter and temperature profile system.1. According to the measurements at various surface condition, such as sea surface, paddy field farm land and bare soil, it is found that influence of solar radiation change is most sensitive to heat capacity of the surface. The surface boundary layer over sea surface is less sensitive to solar radiation change.2. Based on the measurements over paddy field, turbulent flux of sensible heat is mostly influenced by radiation change and water vapor flux and carbon dioxide flux are less sensitive. We should take into account of plant physiology when surface vegitation are observed.3. Temperature fluctuations were observed at 8 logarithmic levels up to 1.28m from the bare soil surface. It is found that surface temperature responds to solar radiation change with time constant of 2-2.5 minutes. Air temperature follows to surface temperature change. The air temperature at higher levels responds with a small delay than the lower level. The peak of air temperature is not always consistent to surface temperature but it reaches to a peak before the surface temperature maximum.4. The mechanism of surface boundary layer response is found as follows. Surface. temperature changes due to solar radiation change. and increase the temperature turbulence. As a result, sensible heat flux increases and finally it turns to higher air temperature.