Volz F E
Appl Opt. 1993 May 20;32(15):2773-9. doi: 10.1364/AO.32.002773.
In the course of a lengthy series of observations since 1975, a large, continuous decrease of the brightness of the solar aureole has been found west of Boston, at Hanscom Air Force Base and at Lexington, Mass. This points to the virtual disappearance from the lower atmosphere of giant particles larger than ~ 10 microm. in size while total suspended particulates in Boston and other U.S. cities have barely decreased. Results of calculations to better understand the relation between forward scattering and aerosol mass distribution [coarse fraction (CF)] are presented. In addition, a method to modify steep scattering functions calculated for a plane-wave source (Sun treated as a star) to those of the actual (and limb-darkened) Sun is presented. The calculated wavelength dependence of extinction, which is lower than that observed, is found to be little affected by the CF, but seems, like forward scattering, to be sensitive to mass distribution of sizes of < 0.4 and ~ 0.6 microm because of the anomal scattering behavior of spheres.
自1975年以来，在一系列长期观测过程中，在波士顿以西的汉斯科姆空军基地和马萨诸塞州列克星敦发现，日冕亮度出现大幅持续下降。这表明，大气低层中尺寸大于约10微米的大颗粒实际上已消失，而波士顿和美国其他城市的总悬浮颗粒物几乎没有减少。本文给出了为更好理解前向散射和气溶胶质量分布[粗粒部分（CF）]之间关系而进行的计算结果。此外，还提出了一种方法，可将针对平面波源（将太阳视为恒星）计算的陡峭散射函数修正为实际（且边缘变暗）太阳的散射函数。计算得出的消光波长依赖性低于观测值，发现其受CF的影响很小，但似乎与前向散射一样，由于球体的反常散射行为，对尺寸小于0.4微米和约0.6微米的颗粒质量分布敏感。
