Aerosol effects on clouds are concealed by natural cloud heterogeneity and satellite retrieval errors

Area of Science:

• Atmospheric Science
• Climate Science
• Remote Sensing

Background:

• Cloud-mediated aerosol forcing is a major source of climate uncertainty.
• Satellite observations often show decreasing cloud liquid water path (LWP) with increasing cloud droplet number concentration (CDNC).
• Accurately estimating LWP adjustments to aerosol-cloud interactions is crucial but observationally challenging.

Purpose of the Study:

• To investigate the impact of data propagation effects on LWP adjustment estimates.
• To determine if satellite retrieval biases can explain the observed negative LWP-CDNC relationship.
• To re-evaluate the magnitude of aerosol-cloud climate cooling.

Main Methods:

• Analysis of satellite-retrieved cloud properties (optical depth, effective radius).
• Utilizing simulated satellite measurements to isolate error propagation.
• Comparing LWP estimates derived from direct retrievals versus accounting for propagation effects.

Main Results:

• Natural spatial variability and retrieval errors propagate to CDNC and LWP estimates.
• This propagation effect can cause a positive LWP adjustment to be misinterpreted as negative.
• The observed negative LWP-CDNC relationship is likely biased by these propagation effects.

Conclusions:

• The commonly observed negative LWP-CDNC relationship may be an artifact of data processing.
• This bias leads to an underestimation of aerosol-cloud climate cooling.
• Future studies must account for data propagation effects for accurate climate forcing assessments.