New approach for simultaneous estimation of entrainment and detrainment rates in shallow cumuli

 

Submitter

Liu, Yangang — Brookhaven National Laboratory

Area of research

Cloud Processes

Journal Reference

Zhu L, C Lu, S Yan, Y Liu, G Zhang, F Mei, B Zhu, J Fast, A Matthews, and M Pekour. 2021. "A new approach for simultaneous estimation of entrainment and detrainment rates in non‐precipitating shallow cumulus." Geophysical Research Letters, 48(15), e2021GL093817, 10.1029/2021GL093817.

Science

Cloud entrainment is the mixing of environmental air into the cloud, and cloud detrainment is the mixing of cloudy air into the environment. The rates of these two processes are critical to the evolution of cumulus clouds and must be accurately represented in atmospheric and climate models. However, few observational studies are available of these process rates, particularly for detrainment rate. Presented here is the first approach to simultaneously estimate the entrainment and detrainment rates in shallow cumulus clouds from aircraft measurements.

Impact

The new approach enables first-time estimates of entrainment and detrainment rates from aircraft measurements. The new data will shed light on the physical understanding of shallow cumulus clouds needed to improve their representations in climate models.

Summary

A new approach is developed for estimating entrainment and detrainment rates in cumulus clouds based on aircraft observations. The approach is applied to data from the Holistic Interactions of Shallow Clouds, Aerosols, and Land-Ecosystems (HI-SCALE) field campaign, supported by the U.S. Department of Energy's Atmospheric Radiation Measurement user facility. The results show that both entrainment and detrainment rates decrease with increasing height in the cloud. A partial correlation analysis indicates that entrainment rate is positively correlated with environmental relative humidity (RH), while the detrainment rate has a weak negative correlation with environmental RH and a positive correlation with entrainment rate. This analysis can be expanded to other data sets to obtain a comprehensive picture of entrainment and detrainment rates in cumulus clouds. The results shed new light on the relationships of entrainment and detrainment rates needed to improve their representations in climate models.