Title: Observational study of the relationship between entrainment rate and relative dispersion in deep convective clouds

Abstract

We investigate the influence of entrainment rate (λ) on relative dispersion (ε) of cloud droplet size distributions (CDSD) in the 99 growing precipitating deep convective clouds during TOGA-COARE. The results show that entrainment suppresses ε, which is opposite to the traditional understanding that entrainment-mixing broadens CDSD. To examine how the relationship between ε and λ is affected by droplets with different sizes, CDSDs are divided into three portions with droplet radius < 3.75 μm (N₁), radius in the range of 3.75–12.75 μm (N₂) and 12.75–23.25 μm (N₃), respectively. Our results indicate that although the droplet concentration at different sizes generally decrease simultaneously as λ increases, the variation of standard deviation (σ) depends mainly on N₃, while the mean radius (r_m) decreases with decreasing N₃, but increases with decreasing N₁. So the influence of entrainment on CDSD causes a more dramatical decrease in σ than that in r_m, and further leads to the decrease of ε as entrainment enhances. In addition, a conceptual model of CDSD evolution during entrainment-mixing processes is developed to illustrate the possible scenarios entailing different relationships between ε and λ. The number concentration of small droplets and the degree of evaporation of small droplets are found tomore » be key factors that shift the sign (i.e., positive or negative) of the ε-λ relationship.« less

Authors:

Guo, Xiaohao ^[1]; Lu, Chunsong ^[2]; Zhao, Tianliang ^[3]; Liu, Yangang ^[4]; Zhang, Guang Jun ^[5]; Luo, Shi ^[3]

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+ Show Author Affiliations

1. Nanjing Univ. (China). Ministry of Education (ELME), Joint International Research Lab. of Climate and Enviroment Change (ILCEC), Collaborative Innovation Center on Forecast and Education of Meteorological Disasters, Key Lab. for Aerosol-Cloud-Precipitation of China Meteorological Administration; Suzhou Meteorological Bureau, Suzhou (China)
2. Nanjing Univ. (China). Ministry of Education (ELME), Joint International Research Lab. of Climate and Enviroment Change (ILCEC), Collaborative Innovation Center on Forecast and Education of Meteorological Disasters, Key Lab. for Aerosol-Cloud-Precipitation of China Meteorological Administration; Tsinghua Univ., Beijing (China). Ministry of Education Key Lab. for Earth System Modeling, Dept. of Earth System Science
3. Nanjing Univ. (China). Ministry of Education (ELME), Joint International Research Lab. of Climate and Enviroment Change (ILCEC), Collaborative Innovation Center on Forecast and Education of Meteorological Disasters, Key Lab. for Aerosol-Cloud-Precipitation of China Meteorological Administration
4. Brookhaven National Lab. (BNL), Upton, NY (United States). Environmental and Climate Science Dept.
5. Univ. of California, San Diego, CA (United States). Scripps Inst. of Oceanography

Publication Date:

2017-09-23

Research Org.:

Brookhaven National Lab. (BNL), Upton, NY (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:

1399679

Alternate Identifier(s):

OSTI ID: 1549220

Report Number(s):

BNL-114389-2017-JA
Journal ID: ISSN 0169-8095; R&D Project: 2019‐BNL-EE630EECA-Budg; KP1701000

Grant/Contract Number:  

SC0012704; SC00112704; 2015-JY-011; BRA2016424

Resource Type:

Accepted Manuscript

Journal Name:

Atmospheric Research

Additional Journal Information:

Journal Volume: 199; Journal Issue: C; Journal ID: ISSN 0169-8095

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES