The spectral nature of Earth's reflected radiation: measurement and science applications

Abstract: This paper introduces the aerosol, clouds, convection and precipitation (ACCP) program that is currently in the process of defining a number of measurement objectives for NASA that are to be implemented toward the end of the current decade. Since a (solar) visible-shortwave infrared (VSWIR) spectrometer is being considered as part of the ACCP architecture, illustrations of the different ways these measurements will contribute to this program and how these measurements can be expected to advance the science objectives of ACCP are highlighted. These contributions range from 1) constraining cloud radiative process and related estimates of radiative fluxes, 2)scene discrimination, 3) providing aerosol and cloud optical properties, and 4) providing other enhanced information such as the phase of water in clouds, and total column water vapor. The spectral measurements also offer new capabilities that will further enhance the ACCP science such as the discrimination of dust aerosol and the potential for the vertical profiling cloud droplet size in shallow clouds. The areas where the maturity of approaches is lacking is also highlighted as a way of emphasizing research topics to be a focus in the coming years.

摘要：本文介绍了气溶胶、云、对流与降水（Aerosol, Clouds, Convection and Precipitation，下称ACCP）计划，该计划目前正为美国国家航空航天局（NASA）拟定多项观测目标，拟于本十年末付诸实施。鉴于太阳可见光-短波红外（solar visible-shortwave infrared, VSWIR）光谱仪被纳入ACCP体系架构的候选方案，本文重点阐释了此类观测在该计划中的多维度应用场景，以及其对推进ACCP科学目标的潜在价值。此类观测的贡献涵盖以下方面：1）约束云辐射过程及相关辐射通量估算；2）场景识别；3）提供气溶胶与云的光学特性参数；4）补充其他增强型信息，例如云中水相态以及大气总柱水汽含量。光谱观测还将为ACCP科学研究带来全新能力，进一步拓展研究边界，例如实现沙尘气溶胶的区分识别，以及在浅云中反演云滴粒径垂直廓线的潜力。本文同时着重指出了当前相关方法成熟度有待提升的研究领域，以此明确未来数年需重点聚焦的科研方向。