Aerosol breezes drive cloud and precipitation increases.

Area of Science:

• Atmospheric Science
• Climate Science
• Meteorology

Background:

• Aerosol-cloud interactions are a key uncertainty in climate models.
• Mesoscale aerosol variability, particularly around sources like wildfires and cities, is understudied.
• Spatial aerosol distributions significantly modulate climate feedbacks.

Purpose of the Study:

• To observe and model the impact of mesoscale aerosol gradients on cloud formation and precipitation.
• To investigate the phenomenon of an "aerosol breeze" driven by horizontal aerosol variations.
• To assess potential biases in climate models due to unrepresented mesoscale aerosol heterogeneity.

Main Methods:

• Observation of covarying mesoscale aerosol and cloud distributions.
• Utilizing a high-resolution process model to simulate aerosol-driven circulations.
• Comparing results from heterogeneous aerosol distributions with homogenous ones.

Main Results:

• Horizontal aerosol gradients of approximately 100 km drive a thermally-direct "aerosol breeze" circulation.
• Aerosol breezes initiate clouds and precipitation in low-aerosol areas and suppress them in high-aerosol areas.
• Mesoscale aerosol heterogeneity enhances overall cloudiness and precipitation compared to uniform distributions.

Conclusions:

• Mesoscale aerosol gradients significantly impact local and domain-wide cloud and precipitation patterns.
• The "aerosol breeze" effect demonstrates a novel mechanism linking aerosol heterogeneity to atmospheric dynamics.
• Current climate models may exhibit biases if they do not adequately represent mesoscale aerosol heterogeneity.