Cloud albedo changes in response to anthropogenic sulfate and non-sulfate aerosol forcings in CMIP5 models

Abstract

<p><strong>Abstract.</strong> The effects of different aerosol types on cloud albedo are analyzed using the linear relation between total albedo and cloud fraction found on monthly mean scale in regions of subtropical marine stratocumulus clouds, and the influence of Aerosol Optical Depth (AOD) on this relation. Model experiments from the Coupled Model Intercomparison Project phase 5 (CMIP5) are used to separately study the responses to increases in sulfate, non-sulfate and all anthropogenic aerosols. A cloud brightening on month-to month scale due to variability in the background aerosol is found to dominate even in the cases where anthropogenic aerosols are added. The aerosol composition is found to be of importance for this cloud brightening, that is thereby region dependent. There is indication that absorbing aerosols to some extent counteract the cloud brightening, but scene darkening with increasing aerosol burden is generally not supported, even in regions where absorbing aerosols dominate. Regional, monthly mean cloud albedo is found to increase with the addition of anthropogenic aerosols, and more so with sulfate than non-sulfate. The changes in AOD due to anthropogenic aerosols are typically small compared to the AOD variability within a given aerosol forcing scenario, and the magnitude of the change in cloud albedo due to anthropogenic aerosols is small and not directly related to the strength of the month-to-month cloud brightening due to aerosols. The diversity in changes in cloud albedo in this set of models is rather related to the different changes in cloud water content between the experiments.</p>

Phytoplankton Impact on Marine Cloud Microphysical Properties Over the Northeast Atlantic Ocean

“…The correlation coefficients between CDNC and normalized albedo (normalized COD) are equal to 0.50 (0.43). Our data show that the most important microphysical parameter in controlling cloud albedo is LWC, in agreement with previous studies (Frey et al., 2017; Liu et al., 2020). LWC accounts for up to 53% ( R = 0.73; slope = 0.85; intercept = 0.06) of the albedo variance (Figure S18 in Supporting Information ).…”

“…It is well established that cloud albedo and COD in liquid clouds are primarily a function of liquid water path (Frey et al., 2017), therefore any modifications of cloud optical properties attributable to aerosol‐induced microphysical perturbations must be evaluated along with possible adjustments of cloud macrophysical properties. We have studied the relationship of cloud geometrical parameters (H base , H top and H thick ), LWC, albedo, and COD retrieved at MHD by the SYRSOC algorithm with N a and CHL, along with the main meteorological parameters controlling the occurrence of stratiform clouds in this area of the world ocean (Table 1).…”

Simulation study on the indirect effect of sulfate on the summer climate over the eastern China monsoon region

“…The cloud-liquid water path (LWP) is an important variable for cloud properties that can be affected by the aerosol second indirect effect 24 , 39 . The increase in the LWP is because an increased amount of smaller droplets may lead to a reduction in the precipitation efficiency, which is related to the aerosol cloud lifetime effect 7 .…”