Entrainment and mixing processes and their effects on cloud microphysics in the continental stratocumulus clouds observed in Oklahoma during the RACORO campaign are analyzed in the frame of homogeneous and inhomogeneous mixing concepts by combining the approaches of microphysical correlation, mixing diagram, and transition scale (number). A total of 110 horizontally penetrated cloud segments is analyzed. Mixing diagram and cloud microphysical relationship analyses show homogeneous mixing trait of positive relationship between liquid water content (L) and mean volume of droplets (V) (i.e., smaller droplets in more diluted parcel) in most cloud segments. Relatively small temperature and humidity differences between the entraining air from above the cloud top and cloudy air and relatively large turbulent dissipation rate are found to be responsible for this finding. The related scale parameters (i.e., transition length and transition scale number) are relatively large, which also indicates high likelihood of homogeneous mixing. Clear positive relationship between L and vertical velocity (W) for some cloud segments is suggested to be evidence of vertical circulation mixing, which may further enhance the positive relationship between L and V created by homogeneous mixing.
Bibliographical noteFunding Information:
This work is funded by the Korea Meteorological Administration Research and Development Program [Grant KMIPA 2015-2061]. Data used in this article are from the U.S. Department of Energy ARM Aerial Facility's RACORO campaign (http://www.arm.gov/). Lu is supported by the National Natural Science Foundation of China (No. 91537108). Liu is supported by the U.S. Department of Energy's BER Atmospheric System Research (ASR) Program via DE-SC00112704.
All Science Journal Classification (ASJC) codes
- Atmospheric Science