Decadal changes in aerosol optical thickness and single scattering albedo estimated from ground‐based broadband radiometers: A case study in Japan
Decadal changes in aerosol optical thickness and single scattering albedo estimated from ground‐based broadband radiometers: A case study in Japan
复制标题
DOI：
10.1029/2010jd014911
复制
发表时间：
2011-02
影响因子：
--
通讯作者：
R. Kudo;A. Uchiyama;A. Yamazaki;Tomonori Sakami;Osamu Ijima
中科院分区：
文献类型：
--
作者：
R. Kudo;A. Uchiyama;A. Yamazaki;Tomonori Sakami;Osamu Ijima
[1]提出了一种利用宽带直射辐射和漫反射辐射估算气溶胶光学厚度和单次散射辐射的方法。利用模拟的有误差和无误差的辐照度，在可见光区，估算光学厚度的精度为0.7 ~ 0.8 μm，单次散射的精度为0.02 ~ 0.05。由此得到的光学厚度和单次散射随时间的变化与天空辐射计的反演结果吻合得很好。利用所描述的方法估算了1975年至2008年日本筑波大气光学厚度和单次散射的长期变化。光学厚度增加，直到20世纪80年代中期，然后下降，直到20世纪90年代末，并在21世纪初几乎保持不变。在1980年代后期之前，单次散射的散射系数约为0.8，之后逐渐增加，自1990年代中期以来一直保持在约0.9。根据估算的气溶胶光学特性计算的晴空条件下的地面总辐照度表明，在20世纪80年代中期左右有一个明显的从变暗到变亮的过渡。增亮的幅度约为12.7 W m−2;其中8.3 W m−2是由于光学厚度的减少，其余4.4 W m−2是由于单次散射的增加。另一方面，在多云条件下测得的地面总辐照度增加了2.6 W m−2。气溶胶的明暗变化被云层的变化所减弱。所描述的方法可能是有用的，在世界各地的许多网站的表面太阳辐射的长期变化的气溶胶的影响进行评估。
[1] A method to estimate aerosol optical thickness and single scattering albedo from broadband direct and diffuse irradiances was developed. Using irradiances simulated with and without errors, the accuracies of estimated optical thickness from 0.7 to 0.8 μm and single scattering albedo in the visible wavelength region were determined to be about 0.02 and 0.05, respectively. Resulting time variations in optical thickness and single scattering albedo by broadband radiometers agreed well with sky radiometer retrievals. Long-term variations in optical thickness and single scattering albedo from 1975 to 2008 at Tsukuba, Japan, were estimated by the method described. Optical thickness increased until the mid-1980s, then decreased until the late 1990s, and was almost constant in the 2000s. The single scattering albedo was about 0.8 until the late 1980s, gradually increased, and has remained at approximately 0.9 since the mid-1990s. The surface global irradiance under clear sky conditions calculated from estimated aerosol optical properties showed an apparent transition from dimming to brightening around the mid-1980s. The magnitude of the brightening was about 12.7 W m−2; of this, 8.3 W m−2 was due to a decrease in optical thickness, and the remaining 4.4 W m−2 was due to an increase of single scattering albedo. On the other hand, the surface global irradiance measured under cloudy conditions increased by 2.6 W m−2. The dimming and brightening by aerosols were weakened by the changes in clouds. The method described could be useful in evaluating aerosol influences on long-term changes in the surface solar radiation at many sites around the world.