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Entrainment of aerosols and their activation in shallow cumulus clouds - Large-Eddy Simulations with an Embedded Lagrangian Particle Model

浅积云中气溶胶的夹带及其活化 - 使用嵌入式拉格朗日粒子模型进行大涡模拟

基本信息

批准号：
252353065
负责人：
Professor Dr. Siegfried Raasch
金额：
--
依托单位：
Leibniz-Institut für Troposphärenforschung e.V. (TROPOS)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2014
资助国家：
德国
起止时间：
2013-12-31 至 2016-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/252353065?language=en
关键词：
Entrainment aerosols their activation shallow

项目摘要

Shallow cumulus clouds are affecting the climate in many ways. One main impact is the reflection of extraterrestrial shortwave radiation (albedo), which is regulated by the amount and spectral distribution of cloud droplets and, therefore, the amount of aerosols. However, only activated aerosols can serve as condensation nuclei for cloud droplets. Primary activation of aerosols takes place at the cloud base by the adiabatic cooling of rising air parcels. For the activation above cloud base (secondary activation) two explanations exist: (i) the activation of aerosols, which are too small to be activated at cloud base, and (ii) the lateral entrainment of aerosols into the cloud and their subsequent activation in the supersaturated environment of the cloud. The general objective of the current project is to obtain an improved understanding of the processes which lead to the activation of aerosols in shallow cumulus by applying large-eddy simulations (LES) with an embedded Lagrangian particle model (LPM) to parameterize cloud physics, in which Lagrangian particles (so-called super-droplets) represent a certain number of real droplets/aerosols with same features (e. g., droplet size, aerosol mass). This Lagrangian perspective of cloud physics allows tracking of individual droplets/aerosols and the direct calculation of entrainment rates. This is required and will be used to quantify how the different processes of activation contribute to the number of cloud droplets during thelife-cycle of an individual cloud, in a cloud ensemble (i. e., dependencies on cloud features like cloud height) or under different background aerosol conditions (maritime and continental).

浅层积云在许多方面影响着气候。一种主要影响是地外短波辐射(反照率)的反射，这受云滴的数量和光谱分布以及气溶胶的数量和分布的调节。然而，只有活化的气溶胶才能作为云滴的凝结核。气溶胶的初级激活发生在云底，上升的气团的绝热冷却。对于云底以上的激活(二次激活)，有两种解释：(1)气溶胶的激活，它太小而不能在云底激活；(2)气溶胶的侧向夹带进入云中，然后在云的过饱和环境中激活。当前项目的总体目标是通过应用嵌入拉格朗日粒子模型(LPM)的大涡模拟(LES)来参数化云物理，其中拉格朗日粒子(所谓的超级液滴)代表具有相同特征(例如，液滴大小、气溶胶质量)的一定数量的真实液滴/气溶胶，从而更好地了解导致浅层积云中气溶胶激活的过程。这种拉格朗日的云物理观点允许跟踪单个水滴/气溶胶，并直接计算夹带率。这是必需的，并将被用来量化不同的激活过程如何在单个云的生命周期中、在整个云系中(即对云高度等云特征的依赖性)或在不同的背景气溶胶条件(海洋和大陆)下对云滴的数量作出贡献。