Abstract
AbstractA new method for determining clear‐sky shortwave aerosol direct radiative effects (ADRE) from the Clouds and the Earth's Radiant Energy System is used to examine changes in ADRE since 2002 alongside changes in aerosol optical depth (AOD) from the Moderate Resolution Spectroradiometer. At global scales, neither ADRE nor AOD show a significant trend. Over the northern hemisphere (NH), ADRE increases by 0.18 ± 0.17 Wm−2 per decade (less reflection to space) but shows no significant change over the southern hemisphere. The increase in the NH is primarily due to emission reductions in China, the United States, and Europe. The COVID‐19 shutdown shows no noticeable impact on either global ADRE or AOD, but there is a substantial influence over northeastern China in March 2020. In contrast, February 2020 anomalies in ADRE and AOD are within natural variability even though the impact of the shutdown on industry was more pronounced in February than March. The reason is because February 2020 was exceptionally hot and humid over China, which compensated for reduced emissions. After accounting for meteorology and normalizing by incident solar flux, February ADRE anomalies increase substantially, exceeding the climatological mean ADRE by 23%. February and March 2020 correspond to the only period in which adjusted anomalies exceed the 95% confidence interval for 2 consecutive months. Distinct water‐land differences over northeastern China are observed in ADRE but not in AOD. This is likely due to the influence of surface albedo on ADRE in the presence of absorbing aerosols.
Highlights
Climate is fueled by how much of the sun's energy is absorbed by Earth
Increases in aerosol direct radiative effects (ADRE) and decreases in aerosol optical depth (AOD) occur over China, the United States, South America, and Europe
The ADRE is determined with a new approach that uses a SW decomposition technique that enables attribution of ADRE changes in terms of atmospheric and surface albedo changes
Summary
Climate is fueled by how much of the sun's energy is absorbed by Earth. Emission of aerosols into the atmosphere, whether natural or anthropogenic, has a direct impact on how much solar energy is reflected, absorbed, and transmitted by the atmosphere. Under cloud-free conditions, which occurs roughly one-third of the time globally, the dominant radiative effects of aerosols are the reflection of incident solar radiation back to space and direct absorption of sunlight in the atmosphere. These reduce how much solar energy is available at the surface, affecting atmospheric circulation and turbulent heat exchanges between the surface and atmosphere (Evan et al, 2011; Ramanathan et al, 2001). We use observations from CERES and MODIS to examine changes in clear-sky aerosol direct radiative effect (ADRE) and aerosol optical depth (AOD) between July 2002 and March 2020 at global and regional scales.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
