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Across-track Extension of Retrieved Cloud and Aerosol Properties for the EarthCARE Mission: The ACM-3D Product
Atmospheric Measurement Techniques ( IF 3.8 ) Pub Date : 2022-11-21 , DOI: 10.5194/amt-2022-301
Zhipeng Qu, Howard W. Barker, Jason N. S. Cole, Mark W. Shephard

Abstract. The narrow cross-section of cloud and aerosol properties retrieved by L2-algorithms that operate on data from EarthCARE’s nadir-pointing sensors gets “broadened” across-track by an algorithm that is described and demonstrated here. This Scene Construction Algorithm (SCA) consists of four sub-algorithms. At its core is a radiance-matching procedure that works with measurements made by EarthCARE’s Multi-Spectral Imager (MSI). In essence, an off-nadir pixel gets filled with retrieved profiles that are associated with a (nearby) nadir pixel whose MSI radiances best match those of the off-nadir pixel. The SCA constructs a 3D array of cloud and aerosol (and surface) properties for entire frames that measure ~6,000 km along-track by 150 km across-track (i.e., the MSI’s full swath). Constructed domains out to ~15 km on both sides of nadir are used explicitly downstream as input for 3D radiative transfer models that predict top-of-atmosphere (TOA) broadband solar and thermal fluxes and radiances. These quantities are compared to com-mensurate measurements made by EarthCARE’s BroadBand Radiometer (BBR), thus facilitating a continuous closure assessment of the retrievals. Three 6,000 km x 200 km frames of synthetic EarthCARE observations were used to demonstrate the SCA. The main conclusion is that errors in modelled TOA fluxes that stem from use of 3D domains produced by the SCA are expected to be less than ±5 W m-2 and rarely larger than ±10 W m-2. As such, the SCA, as purveyor of in-formation needed to run 3D radiative transfer models, should help more than hinder the radiative closure assessment of EarthCARE’s L2 retrievals.

中文翻译:

为 EarthCARE 任务检索的云和气溶胶特性的跨轨道扩展:ACM-3D 产品

摘要。云和气溶胶特性的狭窄横截面由 L2 算法检索,该算法对来自 EarthCARE 的天底指向传感器的数据进行操作,并通过此处描述和演示的算法在跨轨道上“加宽”。该场景构建算法(SCA) 由四个子算法组成。其核心是辐射匹配程序,可与 EarthCARE 的多光谱成像仪 (MSI) 进行的测量配合使用。本质上,一个最低点以外的像素会被检索到的配置文件填充,这些配置文件与(附近的)最低点像素相关联,其 MSI 辐射与最低点以外的像素最匹配。SCA 为整个帧构建云和气溶胶(和表面)属性的 3D 阵列沿轨道测量约 6,000 公里,跨轨道测量 150 公里(即 MSI 的全幅)。天底点两侧约 15 公里的构造域在下游明确用作 3D 辐射传输模型的输入,该模型预测大气顶层 (TOA) 宽带太阳和热通量和辐射率。将这些数量与 EarthCARE 的宽带辐射计 (BBR) 进行的相应测量进行比较,从而促进对检索的连续关闭评估。三个 6,000 公里 x 200 公里的合成 EarthCARE 观测框架用于演示 SCA。主要结论是,由于使用 SCA 产生的 3D 域而导致的建模 TOA 通量误差预计小于 ±5 W m -2并且很少大于 ±10 W m -2. 因此,作为运行 3D 辐射传输模型所需信息的提供者,SCA 应该有助于而不是阻碍 EarthCARE 的 L2 反演的辐射闭合评估。
更新日期:2022-11-23
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