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Understanding the Microphysical Control and Spatial-Temporal Variability of Warm Rain Probability Using CloudSat and
Zhibo Zhang1,2, Lazaros Oreopoulos3, Matthew D Lebsock4
1Physics Department UMBC Baltimore MD USA.
Geophysical Research Letters
|July 22, 2022
Summary
We developed a new method to understand how cloud properties like liquid water path and droplet number concentration influence precipitation probability in tropical marine low clouds. This helps identify causes of precipitation biases in climate models.
Area of Science:
- Atmospheric Science
- Cloud Physics
- Climate Modeling
Background:
- Marine low clouds play a critical role in Earth's energy budget.
- Accurate representation of cloud microphysics is crucial for climate model projections.
- Understanding precipitation formation in these clouds is a persistent challenge.
Purpose of the Study:
- To develop a parameterization scheme quantifying the influence of liquid water path (LWP) and cloud droplet number concentration (CDNC) on precipitation probability (PoP).
- To investigate the spatial-temporal variations of PoP in tropical marine low clouds using combined satellite data.
- To diagnose the root causes of warm rain biases in global climate models.
Main Methods:
- Combined measurements from Moderate Resolution Imaging Spectroradiometer (MODIS) and CloudSat radar.
- Developed a bivariate probability of precipitation (PoP) function based on LWP and CDNC.
- Conducted sensitivity tests using the developed parameterization scheme.
Main Results:
- Spatial-temporal variations in grid-mean in-cloud
are largely explained by the joint probability density function of LWP and CDNC. - Stratocumulus to cumulus transitions in the Southeastern Pacific and Atlantic are primarily driven by CDNC variations.
- The annual cycle of
is mainly influenced by LWP variations.
Conclusions:
- The developed parameterization scheme effectively quantifies microphysical controls on precipitation probability.
- Identified distinct roles of CDNC and LWP in driving precipitation changes in marine low clouds.
- Provides a viable method for diagnosing and improving warm rain parameterizations in climate models.
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