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[1] Equivalent optical depths of a standard continental aerosol model are defined as the indexes for atmospheric optical depths of absorption and scattering (ODA and ODS, respectively) under clear-sky condition and can be calculated with the routinely observed data of broadband surface solar irradiances. The ODS by definition is a proxy of the scattering component of atmospheric aerosol optical depth (AOD) and is shown to be largely free from influences of systematic errors of the radiation observing instruments and uncertainties in atmospheric absorption. The ODA accounts for contributions of aerosols, water vapor, and other gases with profiles deviating from the standard atmosphere model. Applied to the data from 36 observatories of China, from 1957 to 2007, the method provides the long-term variations of clear-sky atmospheric absorption and scattering, which are qualitatively compared with other AOD estimations with comparable regional and temporal coverage. The results show the method reasonably separates the absorption and scattering effects and captures the general features of their seasonal variation. The radiation dimming trend over China region during about 1970-1990 is shown to be associated with the increasing ODA and ODS. After 1990, there is not a significant trend in ODS but the ODA has been slightly decreased.Citation: Wang, B., and G. Shi (2010), Long-term trends of atmospheric absorbing and scattering optical depths over China region estimated from the routine observation data of surface solar irradiances,

Previous studies have shown that the mechanical effects of vegetation roots on slope stability can be classified as additional cohesion effects and anchorage effects. The present study investigated the combined mechanical effects (additional cohesion effects and anchorage effects) of vegetation on a slope with coarse-grained soil in the mountainous region (significantly prone to slope failure) of Gansu Province, China. A detailed survey of tree density, root system morphology and slope profiles was conducted, and we also assessed the soil cohesion provided by the root systems of monospecific stands of Robinia pseudoacacia growing in different locations on the slope. The measured data were incorporated into a numerical slope model to calculate the stability of the slope under the influence of trees. The results indicated that it was necessary to consider the anchoring effect of coarse roots when estimating the mechanical effects of trees on slope stability. In particular, the FoS (factor of safety) of the slope was increased by the presence of trees. The results also demonstrated that vegetation increased slope stability. The reinforcing effects were most significant when the trees were planted along the entire slope. Although the reinforcing effects contributed by trees were limited (only 4–11%), they were essential for making optimal use of vegetation for enhancing slope stability. Overall, vegetation development can make a major contribution to ecosystem restoration in the study region.