Cloud Halos and their Roles in the Atmospheric Radiation Balance and Climate

最近的观测表明，越来越大的积云周围的空气有时几乎被水蒸气饱和。计算表明，云层周围的这些蒸汽层或“光晕”可以显著增加对太阳辐射的吸收。该项目的目的是高精度和高分辨率地测量积云周围的水汽场，并将这些信息用于辐射传输的计算和评估云-环境相互作用对云微物理的影响。具体目标如下：-以足够的细节测量对流云及其周围的水汽场，以表征相对于云边的三维水汽结构；-同时测量云晕内气溶胶的尺寸分布、组成和光学性质；-分析所产生的测量结果，以便提供几个完整的记录案例用于辐射传输计算；-进行辐射传输分析，包括对观察到的水蒸气、气溶胶和云的分布进行吸收和加热率计算；-为了确定辐射分析对气候模拟的影响，将使用CIRPAS双水獭飞机进行测量，该飞机配备了由Aerodyne Research开发的名为Fast Water Vapor Monitor的新仪器，以及测量气溶胶、CCN、云滴和液态水含量的仪器。辐射传输计算将使用不同复杂程度的计算机代码。这一结果与异常云吸收问题有关，异常云吸收是指观测到的云对太阳的吸收与应用米氏散射理论计算的云滴群体吸收之间的差异。这是加州理工大学和Aerodyne Research，Inc.的合作研究项目。合作的Aerodyne部分由自动取款机-9910744，约翰·T·杰恩博士支持。

Recent observations indicate that the air surrounding growing cumulus clouds is sometimes nearly saturated with water vapor. Calculations show that these vapor shrouds or "halos" around clouds can account for a significant increase in the absorption of solar radiation. The purpose of this project is to measure the vapor field around cumulus clouds with high accuracy and resolution and to use the information in calculations of radiative transfer and in assessing the consequences of cloud-environment interactions on cloud microphysics. The specific objectives are as follows:- To measure the vapor field in and around convective clouds with sufficient detail to characterize the 3-dimensional vapor structure relative to cloud edges;- To measure concurrently the size distribution, composition, and optical properties of aerosols within the cloud halo;- To analyze the resulting measurements in order to provide several completely documented cases for use in radiative transfer calculations;- To carry out radiative transfer analyses including absorption and heating rate calculations for the observed distributions of water vapor, aerosols, and cloud;- To determine the implications of the radiation analysis for climate modeling.The measurements will be conducted with the CIRPAS Twin Otter aircraft, equipped with a new instrument called the Fast Water Vapor Monitor developed by Aerodyne Research along with instruments for measuring aerosols, CCN, cloud droplets, and liquid water content. Computer codes with different degrees of complexity will be used for the radiative transfer calculations. The results bear on the question of anomalous cloud absorption, which refers to the discrepancies that have been observed between the observed solar absorption by clouds and the absorption calculated using Mie scattering theory applied to populations of cloud drops. This is a collaborative research project between Cal Tech and Aerodyne Research, Inc. The Aerodyne component of the collaboration is supported by ATM-9910744, Dr. John T. Jayne, PI.