Cloud fraction response to aerosol driven by nighttime processes.

Area of Science:

• Atmospheric Science
• Climate Science
• Cloud Physics

Background:

• Aerosol-cloud interactions are a major source of uncertainty in climate forcing.
• Stratocumulus clouds, crucial for climate, are influenced by diurnal cycles, yet studies often neglect nighttime behavior.
• Understanding aerosol impacts on cloud fraction and liquid water path is vital for climate modeling.

Purpose of the Study:

• To investigate the diurnal variation in cloud sensitivity to aerosols in stratocumulus clouds.
• To differentiate the roles of nighttime and daytime processes in aerosol-cloud interactions.
• To improve climate models by incorporating a more accurate representation of aerosol effects on clouds.

Main Methods:

• Utilized a Lagrangian framework to analyze day-night variations in cloud properties.
• Characterized the sensitivity of cloud fraction and liquid water path to aerosols.
• Compared model-observation data, focusing on diurnal cycle representation.

Main Results:

• Cloud fraction response to aerosols is primarily driven by nighttime processes.
• Aerosols reduce daytime cloud fraction, an effect partially offset by nighttime processes.
• Aerosol-induced precipitation suppression is most effective at night, coinciding with strongest stratocumulus precipitation.

Conclusions:

• Nighttime processes are critical for determining the diurnal evolution of stratocumulus clouds and their radiative impact.
• Accurate representation of the diurnal cycle and nighttime observations are essential for climate forcing assessments.
• Findings inform the viability of marine cloud brightening strategies by highlighting the importance of nighttime cloud dynamics.