银川地区气溶胶特性的天空辐射计测量

Sky radiometer measurements of aerosol properties over Yinchuan,China

利用地基天空辐射计测定了银川地区2003年10月—2004年8月太阳直接辐射和天空散射辐射,采用"SKYRAD"模式同时反演了银川地区气溶胶光学厚度、波长指数、体积谱分布、折射指数和单次散射反照率,并对结果进行了分析。结果表明:银川地区气溶胶光学厚度具有明显的日变化,4个季节的变化范围分别31%、33%、24%和38%,并主要表现出两种变化类型,而光学厚度的季节变化春季最大,冬季最小,波长指数变化与光学厚度变化基本相反,春季最小,冬季最大,这主要与北方沙尘活动有关;气溶胶尺度分布表现出双峰型结构,一种是位于半径0.15μm附近的积聚模态,另一种是半径7μm左右的粗模态,且粗模态浓度远大于积聚模态的浓度;折射指数实部春季明显升高,对波长的敏感性较低,而虚部春季显著下降,并且表现出对波长更低的敏感性,但两者在不同波段的微小变化均表现出了一定的规律性,且虚部表现的更为复杂;单次散射反照率春季显著高于其他季节,并随波长的增加而显著增加,而其他季节单次散射反照率在波长之间虽存在变化,但并没有表现出任何规律性,表明这种变化具有明显的区域性差别。

A ground-based sky radiometer was used to measure direct and diffuse solar irradiances, as well as aureole radiances, from October 2003 to August 2004 over Yinchuan, China. The aerosol optical depth （AOD）, Angstrom exponent （a）, volume size distri- butions, refraction index and single scattering albedo of aerosols were simultaneously retrieved using the SKYRAD model. The diurnal variability of AOD in Yinchuan was significant, with its change amplitude of about 31%, 33 %, 24 % and 38 % in spring, summer, autumn and winter, respectively,and it mainly had two patterns. The AOD varied seasonally with a vernal maximum and a winter minimum, while the variation in a was opposite to AOD, with a vernal minimum and a winter maximum. This is associated with the activities of sandstorms in northern China. The aerosol volume size distributions presented a bimodal structure, i. e. , an accumulation mode with a radius of about 0.15μm and a coarse mode with a radius of about 7 μm. The latter had a concentration far greater than the former. The real part of the refraction index rose dramatically in spring, and exhibited a low sensitivity to wavelength; but its imaginary part decreased noticeably in spring, showing an even lower sensitivity to wavelength, and the variation was more complicated. The aerosol single scattering albedo in spring was much higher than that in other seasons, and increased dramatically with increasing wavelength. In other seasons, the magnitude of the aerosol single scattering albedo showed random small changes with wavelength.