中国西部干旱地区太阳直接辐射通量密度与大气质量的关系

本文根据中国西部干旱地区大气物理状态(大气可降水量和大气浑浊度)的变化范围,利用太阳直接辐射通量密度的理论计算公式,计算了各种大气透明系数状况下的太阳直接辐射通量密度。计算结果表明,大气质量m=2时的透明系数P_2和m相同时,由于水汽和气溶胶的含量配置不同而引起太阳直接辐射通量密度的差异,在辐射日变程的主要时段(m=1-3)内并不大。于是得到各种透明系数P_2状况下太阳直接辐射通量密度随大气质量变化的平均关系。不同海拔高度比较,当透明系数P_2相同时,各自的大气物理状态虽然不同,但m相同时的太阳直接辐射通量密度基本相同。现有的表征太阳直接辐射通量密度值和大气质量联系的关系式都不能很好地描述计算结果。根据太阳直接辐射通量密度随大气质量变化的特性,我们提出了新的关系式。最后,整理了不同拔海高度和不同地理景观的四个日射站(西藏那曲、青海格尔木、甘肃敦煌和民勤)的多年观测资料。经验计算结果与观测值比较,一致性良好。

THE RELATIONSHIP BETWEEN THE FLUX DENSITY OF THE DIRECT SOLAR RADIATION AND THE AIR MASS OVER THE ARID REGION OF THE WEST CHINA

In this paper , based on the variation range of the atmospheric physicics state ( precipitable water and turbidity ) of the arid region of the west China we have computed the flux density of the direct solar radiation under various coefficients of transparency, Using the theoretical computational formula for the direct solar radiation. The computation result shows that if the coefficients of transparency (P2) and the air mass (m) are the same, the differences of the flux density of the direct solar radiation due to the different content of the water vapour and the aerosol are not large in the major time section ( m = 1 ~ 3 )of daily variation of solar radiation. Thus the averaged relationships between the flux density of the direct solar radiation and the air mass under various coefficients of transparency P2 were obtained. If the coefficients of transparency P2 and the mare the same, though the atmospheric physics state are different at different heights above sea-level, the flux density of the direct solar radiation are the same on the whole. All the existed relations of the flux density of the direct solar radiation to the air mass are unable to well depict the results obtained by above computation. Therefore, on the basis of the character of the variation of the flux desity of the direct solar radiation with air mass, a new expression has been presented. Finally, the secular observational data for the four solar radiation stations ( Naqu, Xizang; Gelmud, Qinhai; Dunhuang and Minqin, Gansu ) with different elevations above sea-level geographical landscapes have been analysed. Both the empirical and observed values agree well with each other.