Water vapor plays a key role in weather, climate and environmental research on local and global scales. Knowledge about atmospheric water vapor and its spatiotemporal variability is essential for climate and weather research. Because of the advantage of a unique temporal and spatial resolution, satellite observations provide global or regional water vapor distributions. The advanced Medium Resolution Spectral Imager (MERSI) instrument—that is, MERSI-II—onboard the Fengyun-3D (FY-3D) meteorological satellite, has been one of the major satellite sensors routinely providing precipitable water vapor (PWV) products to the community using near-infrared (NIR) measurements since June 2018. In this paper, the major updates related to the production of the NIR PWV products of MERSI-II are discussed for the first time. In addition, the water vapor retrieval algorithm based on the MERSI-II NIR channels is introduced and derivations are made over clear land areas, clouds, and sun-glint areas over the ocean. Finally, the status and samples of the MERSI-II PWV products are presented. The accuracy of MERSI-II PWV products is validated using ground-based GPS measurements. The results show that the accuracies of the water vapor products based on the updated MERSI-II instrument are significantly improved compared with those of MERSI, because MERSI-II provides a better channel setting and new calibration method. The root-mean-square error and relative bias of MERSI-II PWV products are typically 1.8–5.5 mm and −3.0% to −14.3%, respectively, and thus comparable with those of other global remote sensing products of the same type.

中文翻译：

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风云3D卫星搭载先进中分辨率光谱成像仪近红外通道水汽回收

水蒸气在地方和全球尺度的天气、气候和环境研究中发挥着关键作用。有关大气水汽及其时空变异性的知识对于气候和天气研究至关重要。由于独特的时间和空间分辨率的优势，卫星观测提供了全球或区域水汽分布。风云三号（FY-3D）气象卫星搭载的先进的中分辨率光谱成像仪（MERSI）仪器，即MERSI-II，一直是主要的卫星传感器之一，定期向地球提供可降水量水汽（PWV）产品。自 2018 年 6 月以来，社区使用近红外 (NIR) 测量。本文首次讨论了与 MERSI-II 的 NIR PWV 产品生产相关的主要更新。此外，介绍了基于 MERSI-II NIR 通道的水汽反演算法，并在清晰的陆地区域、云层和海洋上的阳光区域进行了推导。最后，介绍了 MERSI-II PWV 产品的现状和样本。MERSI-II PWV 产品的准确性已使用基于地面的 GPS 测量进行验证。结果表明，与MERSI相比，基于更新后的MERSI-II仪器的水蒸气产物的准确度有显着提高，因为MERSI-II提供了更好的通道设置和新的校准方法。MERSI-II PWV产品的均方根误差和相对偏差通常分别为1.8-5.5 mm和-3.0%至-14.3%，与全球其他同类型遥感产品具有可比性。