Long‐term trends of atmospheric absorbing and scattering optical depths over China region estimated from the routine observation data of surface solar irradiances

Abstract

[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,

The Long-term Variation in Surface Shortwave Irradiance in China and Japan: A Review

“…It was suggested from this analysis that the decreasing trend in the shortwave irradiance in China from 1971 until 1989 was mainly caused by anthropogenic aerosols and the increasing trend from 1990 until 2002 was attributed to changes in both cloud cover and aerosol loading. These results are consistent with those of Wang and Shi (2010) and Qian et al (2006) with regard to the importance of the effect of anthropogenic aerosols on the shortwave irradiance under clear sky conditions. The direct effect of aerosol loading in the sub-cloud layer cannot be ignored if the aerosols have strong absorption properties (Hayasaka et al 2006).…”

“…Datasets from 64 stations were used to confirm that a decrease in surface direct shortwave irradiance occurred during the period , while the diffuse shortwave irradiance did not change over the same period . Using the same data at 36 stations, Wang and Shi (2010) revealed an increase in the levels of atmospheric aerosols over the period 1957-2007 based on an analysis of the global and diffuse shortwave irradiances under clear sky conditions, although the absorbing optical thickness of aerosols could not be separated from the total absorbing optical thickness, which included gaseous absorption. Both the scattering and absorbing optical thicknesses of the clear sky atmosphere leveled off in the early 1990s after the increases in optical thicknesses observed since 1957.…”

Importance of Long-Range Nitrate Transport Based on Long-Term Observation and Modeling of Dust and Pollutants over East Asia

“…Understanding the behavior of long-range trans-boundary transport of dust and pollutants in East Asia is an important environmental issue because of the frequent outflow of heavy PM 2.5 pollution from China (e.g., Wang and Shi, 2010). Ground-base and airborne episodic aerosol observations have been studied to determine the physics and chemistry of high-concentration events (e.g., Carmichael et al, 1997;Huebert et al, 2003;Jacob et al, 2003), but the period of these observation campaigns are typically less than one month, which is insufficient to study seasonal variations.…”

Modeling the relationship between photosynthetically active radiation and global horizontal irradiance using singular spectrum analysis

“…As a result, in many areas strongly affected by biomass burning such as the vast Amazon region of South America or the southern African savannahs for example, few empirical studies have taken place (Tsubo & Walker 2002;Aguiar et al, 2012). Consequently, PAR estimates are derived from radiative transfer models (RTMs) or from application of empirical relationships which usually depend sensitively on local conditions (Gonzalez & Calbo 2002;Gueymard, 2008;Lu et al, 2011;Aguiar et al, 2012;Wang & Shi, 2010;Janjai & Wattan, 2011;Ge et al, 2011). As a result, the advice is to use conversion relationships when combining solar measurements and meteorological parameters (Udo & Aro, 1999;Ross & Sulev, 2000;Gueymard, 1989;Bai, 2012).…”