Distinguishing the impacts of natural and anthropogenic aerosols on global gross primary productivity through diffuse fertilization effect

Abstract

Abstract. Aerosols can enhance ecosystem productivity by increasing diffuse radiation. Such diffuse fertilization effects (DFEs) vary among different aerosol compositions and sky conditions. Here, we apply a suite of chemical, radiation, and vegetation models in combination with ground- and satellite-based measurements to assess the impacts of natural and anthropogenic aerosol species on gross primary productivity (GPP) through DFE during 2001–2014. Globally, aerosols increase GPP by 8.9 Pg C yr-1 at clear skies but only 0.95 Pg C yr-1 at all skies. Anthropogenic aerosols account for 41% of the total GPP enhancement though they contribute only 25% to the increment of diffuse radiation. Sulfate/nitrate aerosols from anthropogenic sources make dominant contributions of 33% (36%) to aerosol DFE at all (clear) skies, followed by the ratio of 18% (22%) by organic carbon aerosols from natural sources. In contrast to other species, black carbon aerosols decrease global GPP by 0.28 (0.12) Pg C yr-1 at all (clear) skies. Long-term simulations show that aerosol DFE is increasing 2.9% yr-1 at all skies mainly because of a downward trend in cloud amount. This study suggests that the impacts of aerosols and cloud should be considered in projecting future changes of ecosystem productivity under varied emission scenarios.

The roles of environmental conditions in the pollutant emission-induced gross primary production change: Co-contribution of meteorological fields and regulation of its background gradients

“…Based on our results, anthropogenic emissions would cause in-homogeneous variations in meteorological fields, which were supported by previous studies but with slight discrepancies. For instance, our results were generally in accordance with the findings of Zhou et al (2022) at the global scale, with the dimming PAR dir lower than 4 W m −2 and 9.6 W m −2 for BC and OC emission, and the brightening PAR dif averaged at 0.57 W m −2 and 0.05 W m −2 for sulfate (include nitrate) and OC. The existed small differences could be primarily attributed to the regional scale and cloud effect.…”

“…However, AOD and CC variations induced by anthropogenic factors remained largely uncertain. Although AOD was raised in highly polluted regions because the lower boundary layer increased atmosphere stability and inhibited pollution diffusion (Iversen et al, 2001), the increase in pollutant emissions might not always increase AOD (Figure S15) (Zhou et al, 2022), depending on the aerosol-induced atmospheric circulation changes, the local anthropogenic population and emissions (Qu et al, 2021), and the interactions between anthropogenic and natural aerosols (Wei et al, 2022).…”

“…China’s varied meteorological conditions, multiple pollutant types, and heavily polluted conditions (Wang et al, 2020, Zhang et al 2021) provide a unique opportunity for studying the response of vegetation photosynthesis to variations in aerosols and sky conditions induced by pollutant emissions at the regional scale. Three typical pollutants with high concentrations and significant influences were chosen to simulate the combined effect of clouds and aerosols under emission scenarios (Yue and Unger, 2017; Zhou et al, 2022). Then, we used the coupled regional climate model and process-based vegetation model, with the objectives of 1) quantifying the short-term impact of different pollutants emission on vegetation production, 2) determining the relative contributions of emission-induced radiation and climatic factors on vegetation photosynthesis, and 3) understanding the influence of background environmental conditions on the photosynthetic sensitivity to key meteorological drivers.…”