Exploring aerosols near clouds with high-spatial-resolution aircraft remote sensing during SEAC⁴RS

Area of Science:

• Atmospheric Science
• Remote Sensing
• Climate Science

Background:

• Aerosols significantly influence Earth's climate system.
• Satellite-borne Moderate-resolution Imaging Spectroradiometer (MODIS) Dark Target (DT) algorithm retrieves aerosol optical depth (AOD) in cloud-free conditions.
• MODIS resolution is insufficient for studying aerosols near clouds.

Purpose of the Study:

• To investigate aerosol variability within cloud systems using high-resolution data.
• To analyze the causes of enhanced AOD observed near clouds.

Main Methods:

• Porting the Dark Target (DT) algorithm to the enhanced-MODIS Airborne Simulator (eMAS) for high-resolution (~50 m pixels) retrievals.
• Utilizing data from the SEAC4RS campaign (2013) including eMAS, Cloud Physics Lidar (CPL), MODIS, and AERONET observations.
• Defining spatial metrics to differentiate near-cloud and far-from-cloud environments.

Main Results:

• High-resolution eMAS retrievals showed enhanced AOD within 6 km of clouds, even with aggressive cloud screening.
• Cloud masking was robust; thin cirrus had minimal impact on retrieved AOD.
• Observed AOD enhancement is partly explained by aerosol swelling in clear-cloud transition zones.

Conclusions:

• Three-dimensional radiative interactions between clouds and the surrounding clear air are the primary driver of enhanced AOD near clouds.
• High-resolution airborne remote sensing is crucial for understanding near-cloud aerosol properties.
• Findings improve the understanding of aerosol-cloud interactions and their climate implications.