globalchange  > 气候减缓与适应
DOI: 10.1002/2017JD027985
Scopus记录号: 2-s2.0-85045293785
论文题名:
On Which Microphysical Time Scales to Use in Studies of Entrainment-Mixing Mechanisms in Clouds
作者: Lu C.; Liu Y.; Zhu B.; Yum S.S.; Krueger S.K.; Qiu Y.; Niu S.; Luo S.
刊名: Journal of Geophysical Research: Atmospheres
ISSN: 2169897X
出版年: 2018
卷: 123, 期:7
起始页码: 3740
结束页码: 3756
语种: 英语
英文关键词: clouds ; entrainment-mixing ; observation ; simulation ; time scales
Scopus关键词: cloud droplet ; cloud microphysics ; concentration (composition) ; mixing ; numerical method ; parameterization ; saturation ; thermodynamics ; time series analysis
英文摘要: The commonly used time scales in entrainment-mixing studies are examined to seek the most appropriate one, based on aircraft observations of cumulus clouds from the RACORO campaign and numerical simulations with the Explicit Mixing Parcel Model. The time scales include the following: τevap, the time for droplet complete evaporation; τphase, the time for saturation ratio deficit (S) to reach 1/e of its initial value; τsatu, the time for S to reach −0.5%; and τreact, the time for complete droplet evaporation or S to reach −0.5%. It is found that the proper time scale to use depends on the specific objectives of entrainment-mixing studies. First, if the focus is on the variations of liquid water content (LWC) and S, then τreact for saturation, τsatu and τphase are almost equivalently appropriate, because they all represent the rate of dry air reaching saturation or of LWC decrease. Second, if one focuses on the variations of droplet size and number concentration, τreact for complete evaporation and τevap are proper because they characterize how fast droplets evaporate and whether number concentration decreases. Moreover, τreact for complete evaporation and τevap are always positively correlated with homogeneous mixing degree (ψ); thus, the two time scales, especially τevap, are recommended for developing parameterizations. However, ψ and the other time scales can be negatively, positively, or not correlated, depending on the dominant factors of the entrained air (i.e., relative humidity or aerosols). Third, all time scales are proportional to each other under certain microphysical and thermodynamic conditions. ©2018. American Geophysical Union. All Rights Reserved.
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资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/114103
Appears in Collections:气候减缓与适应

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作者单位: Key Laboratory of Meteorological Disaster, Ministry of Education (KLME)/Joint International Research Laboratory of Climate and Environment Change (ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters (CIC-FEMD)/Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration, Nanjing University of Information Science and Technology, Nanjing, China; Ministry of Education Key Laboratory for Earth System Modeling and Department for Earth System Science, Tsinghua University, Beijing, China; Environmental and Climate Sciences Department, Brookhaven National Laboratory, Upton, NY, United States; Department of Atmospheric Sciences, Yonsei University, Seoul, South Korea; Department of Atmospheric Sciences, University of Utah, Salt Lake City, UT, United States

Recommended Citation:
Lu C.,Liu Y.,Zhu B.,et al. On Which Microphysical Time Scales to Use in Studies of Entrainment-Mixing Mechanisms in Clouds[J]. Journal of Geophysical Research: Atmospheres,2018-01-01,123(7)
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