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Title: Observational Relationship between Entrainment Rate and Environmental Relative Humidity and Implications for Convection Parameterization

Abstract

Entrainment rate is a critical but highly uncertain quantity in convective parameterizations; especially, the effects of environmental relative humidity on entrainment rate are controversial, or even opposite, in different studies. Analysis of aircraft observations of cumuli from the RACORO and RICO field campaigns shows that entrainment rate is positively correlated with relative humidity. Physical analysis shows that higher relative humidity promotes entrainment by reducing buoyancy in the cloud cores and by weakening downdrafts near the cloud cores. The reduced buoyancy in the cloud cores and weakened downdrafts surrounding the cores further reduce updrafts in the cloud cores; the cloud cores with smaller updrafts are more significantly affected by their environment, resulting in larger entrainment rate. The relationship between entrainment rate and relative humidity is consistent with the buoyancy sorting concept widely used in convection parameterizations. The results provide reliable in situ observations to improve parameterizations of entrainment rate.

Authors:
ORCiD logo [1];  [1]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [4]; ORCiD logo [5];  [1];  [1];  [1]; ORCiD logo [1]
  1. Nanjing Univ. of Information Science and Technology (China)
  2. Brookhaven National Lab. (BNL), Upton, NY (United States)
  3. Univ. of California, San Diego, CA (United States). Scripps Inst. of Oceanography
  4. Tsinghua Univ., Beijing (China)
  5. Chinese Academy of Meteorological Sciences, Beijing (China)
Publication Date:
Research Org.:
Brookhaven National Lab. (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1483556
Report Number(s):
BNL-209495-2018-JAAM
Journal ID: ISSN 0094-8276
Grant/Contract Number:  
SC0012704
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Geophysical Research Letters
Additional Journal Information:
Journal Name: Geophysical Research Letters; Journal ID: ISSN 0094-8276
Publisher:
American Geophysical Union
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES

Citation Formats

Lu, Chunsong, Sun, Cheng, Liu, Yangang, Zhang, Guang J., Lin, Yanluan, Gao, Wenhua, Niu, Shengjie, Yin, Yan, Qiu, Yujun, and Jin, Lianji. Observational Relationship between Entrainment Rate and Environmental Relative Humidity and Implications for Convection Parameterization. United States: N. p., 2018. Web. doi:10.1029/2018GL080264.
Lu, Chunsong, Sun, Cheng, Liu, Yangang, Zhang, Guang J., Lin, Yanluan, Gao, Wenhua, Niu, Shengjie, Yin, Yan, Qiu, Yujun, & Jin, Lianji. Observational Relationship between Entrainment Rate and Environmental Relative Humidity and Implications for Convection Parameterization. United States. doi:10.1029/2018GL080264.
Lu, Chunsong, Sun, Cheng, Liu, Yangang, Zhang, Guang J., Lin, Yanluan, Gao, Wenhua, Niu, Shengjie, Yin, Yan, Qiu, Yujun, and Jin, Lianji. Mon . "Observational Relationship between Entrainment Rate and Environmental Relative Humidity and Implications for Convection Parameterization". United States. doi:10.1029/2018GL080264.
@article{osti_1483556,
title = {Observational Relationship between Entrainment Rate and Environmental Relative Humidity and Implications for Convection Parameterization},
author = {Lu, Chunsong and Sun, Cheng and Liu, Yangang and Zhang, Guang J. and Lin, Yanluan and Gao, Wenhua and Niu, Shengjie and Yin, Yan and Qiu, Yujun and Jin, Lianji},
abstractNote = {Entrainment rate is a critical but highly uncertain quantity in convective parameterizations; especially, the effects of environmental relative humidity on entrainment rate are controversial, or even opposite, in different studies. Analysis of aircraft observations of cumuli from the RACORO and RICO field campaigns shows that entrainment rate is positively correlated with relative humidity. Physical analysis shows that higher relative humidity promotes entrainment by reducing buoyancy in the cloud cores and by weakening downdrafts near the cloud cores. The reduced buoyancy in the cloud cores and weakened downdrafts surrounding the cores further reduce updrafts in the cloud cores; the cloud cores with smaller updrafts are more significantly affected by their environment, resulting in larger entrainment rate. The relationship between entrainment rate and relative humidity is consistent with the buoyancy sorting concept widely used in convection parameterizations. The results provide reliable in situ observations to improve parameterizations of entrainment rate.},
doi = {10.1029/2018GL080264},
journal = {Geophysical Research Letters},
number = ,
volume = ,
place = {United States},
year = {Mon Nov 26 00:00:00 EST 2018},
month = {Mon Nov 26 00:00:00 EST 2018}
}

Journal Article:
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