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This paper presents an analysis of the long‐term (1982–2015) variability of aerosol optical properties, as well as aerosol and greenhouse gases (GHG) direct radiative forcing (RF) in central Europe on the basis of MERRA‐2 reanalysis and ground‐based observation. Calculations of longwave (LW) and shortwave (SW) RF were made with the use of the off‐line Fu‐Liou radiative transfer model and were preceded by the sensitivity study of the code's input parameters. Then, the long‐term mean as well as the annual variability for selected regions of aerosol optical properties and radiative forcing were analysed. The mean AOD trend was −0.056 ± 9% per decade and AOD was reduced by 48% between 1982 and 2015. While for 1982–1990 the trend per decade was −0.12 ± 20%, for 1991–2000 it was −0.17 ± 17% and only −0.02 ± 31% in the last 15 years (2001–2015). The trend of the aerosol radiative forcing (ARF) was 1.52 ± 0.12 W·m−2/10 year and 1.21 ± 0.19 W·m−2/10 year at top of the atmosphere (TOA) and at Earth's surface, respectively. The trend for GHG was significantly smaller and it equalled 0.27 ± 0.01 W·m−2/10 year at TOA and 0.17 ± 0.01 W·m−2/10 year at the surface. Changes in GHG and aerosol direct effect produced additional 3.2 ± 0.2 W·m−2 at TOA, which could be associated with the observed regional climate warming. The change of the direct aerosol effect was about 4 times the GHG RF. The influence of aerosol loading reduction on the radiation budget was significantly higher in the 1990s of the 20th century in comparison to the first decades of the 21st. The effect of aerosol reduction has significant impact on air temperature changes during warm season and negligible during winter. [ABSTRACT FROM AUTHOR]

Using the WRF model with chemistry (WRF-Chem), this study investigates the potential contributions of aerosol direct (ADE) and aerosol indirect (AIE) effects on the nocturnal convective precipitation occurred on 9–10 September 2019 in Beijing. It shows that ADE plays a more important role in spatiotemporal changes of heavy precipitation than AIE in urban areas. Further simulation analyses show that ADE suppresses precipitation by inducing greater surface shortwave radiative cooling and stability before 13:00 (UTC, hereafter) on 9 September, which reduces convective available potential energy (CAPE) losses and then increases the later CAPE. The ADE-induced CAPE increase makes updrafts stronger, increasing cloudiness and transporting more cloud water into the upper troposphere. This, in turn, causes greater latent heat release from freezing and then stronger convection, producing higher rain rate during 13:00–21:00. During 12:00–18:00, AIE causes a decrease in CAPE, which weakens updrafts. AIE decreases the snow mixing ratio above 700 hPa except at 15:00–16:00 on 9 September, which can decrease the release of latent heat from freezing, contributing to the decrease in precipitation after 18:00. Due to the greater stability before 10:00 and the longer time required for updrafts to overcome this stability, ADE necessitates 2–3 h to adjust the simulated rainfall time series. • ADE plays more important roles than AIE in change of heavy precipitation studied. • ADE suppresses daytime precipitation with peak rate delayed by 2 h. • ADE enhances while AIE slightly suppresses nighttime precipitation. [ABSTRACT FROM AUTHOR]

The promotion of renewable energy as a substitute for fossil fuels is the key solution to achieve the goals established during the United Nations Climate Change Conference in Glasgow (COP26) based on which member countries agreed to phase down coal power and achieve net-zero carbon emissions. Among various renewable energy sources, solar energy is an attractive option that will have a significant effect on the future energy supply and energy use. Therefore, we selected the period of 2016–2020 during which the aerosol concentration gradually decreased due to strict pollutant control measures to evaluate solar energy simulations based on the Weather Research Forecast-Chemistry (WRF-Chem) model. We also analyzed the contributions of the aerosol direct effect (ADE), aerosol indirect effect (AIE), and cloud radiation effect (CRE) to solar energy trends by conducting sensitivity experiments. The results show that the WRF-Chem model performs well for the 2 m temperature (T 2), cloud fraction, PM 2.5 , solar energy trends during 2016–2020. There are regional and seasonal differences in the contributions of ADE, AIE, and CRE to solar energy trends, with a decrease in ADE contributions and an increase in CRE contributions from north to south in China, and the AIE contribution being relatively slight. On an annual scale, ADE is the main contributor to the increase in solar energy trends in the Beijing-Tianjin-Hebei (89%) and Fenwei Plains (83.9%) from 2016 to 2020, which is related to the horizontal distribution of PM 2.5. In the Yangtze River Delta and other regions, ADE and CRE contributed equally to the increase in solar energy trends, about 40%. In the Pearl River Delta and Sichuan Basin, the contribution of CRE is larger than that of AIE and ADE, the Pearl River Delta region is the largest contributor of CRE to the annual solar energy trends among the five major urban agglomerations, with a contribution of 78.4%, and Sichuan basin is the only region where CRE has a negative contribution to the annual solar energy trends (−59.1%). On the seasonal scale, the contribution of CRE is dominant except for the greater positive contribution of ADE to the solar energy trends in spring, summer, and autumn in Beijing-Tianjin-Hebei and in autumn in Fenwei Plain. • The WRF-Chem model captures the solar energy trends well • The aerosol effects contributes positively to solar energy trends under strict control of air pollution • The contribution of clouds to solar energy trends is regional and seasonal [ABSTRACT FROM AUTHOR]