We calibrated the integrated water vapor (IWV) data retrieved from near-infrared (NIR) channels of the Ocean and Land Color Instrument (OLCI) onboard the Sentinel-3A satellite using in-situ GPS-sensed IWV observations. Unlike conventional water vapor retrieval methodologies relying upon radiative transfer code, this method utilized a regression equation to empirically estimate GPS IWV from two NIR absorption channels at 900 nm and 940 nm. The GPS IWV data were used as reference to define the relationship between the measured radiance ratio and IWV. We collected IWV data from June 1, 2016 to May 31, 2019 from 453 GPS stations situated in the inland and coastal areas of Australia. The retrieval approach was analyzed by using different sample sizes and training datasets. The evaluation results between June 1, 2019 and May 31, 2020 in Australia indicated that the algorithm could reduce the root-mean-square error (RMSE) of the operational OLCI IWV products by 12.91% from 3.114 to 2.712 mm at the O19 channel, by 10.69% to 2.781 mm at the O20 channel, and by 11.75% to 2.748 mm for the weighted mean IWV when compared with GPS reference IWV data. When compared to European Centre for Medium-Range Weather Forecasts reference IWV data, the RMSE was reduced by 12.94% from 3.154 to 2.745 mm, by 11.04% to 2.805 mm, and by 11.93% to 2.777 mm, at the O19 channel, O20 channel, and the weighted mean, respectively. The spatiotemporal performance of the OLCI IWV measurements was improved in both station-scale and daily-scale after applying the new empirical regression retrieval method. The seasonal and land-surface-type dependence of the retrieval approach was also discussed in this research.

我们使用原位 GPS 感应的 IWV 观测校准了从 Sentinel-3A 卫星上的海洋和陆地颜色仪器 (OLCI) 的近红外 (NIR) 通道获取的综合水汽 (IWV) 数据。与依赖辐射传输代码的传统水汽反演方法不同，该方法利用回归方程从 900 nm 和 940 nm 的两个 NIR 吸收通道凭经验估计 GPS IWV。GPS IWV 数据被用作参考来定义测量的辐射率和 IWV 之间的关系。我们从位于澳大利亚内陆和沿海地区的 453 个 GPS 站收集了 2016 年 6 月 1 日至 2019 年 5 月 31 日的 IWV 数据。通过使用不同的样本大小和训练数据集来分析检索方法。2019年6月1日至5月31日的评估结果，2020 年在澳大利亚表明，该算法可以将 O19 通道的 OLCI IWV 产品的均方根误差 (RMSE) 降低 12.91%，从 3.114 到 2.712 毫米，在 O20 通道降低 10.69% 到 2.781 毫米，以及与 GPS 参考 IWV 数据相比，加权平均 IWV 降低了 11.75% 至 2.748 毫米。与欧洲中期天气预报中心的参考 IWV 数据相比，在 O19 通道，O20 通道，RMSE 从 3.154 降低 12.94% 至 2.745 毫米，降低 11.04% 至 2.805 毫米，降低 11.93% 至 2.777 毫米, 和加权均值。应用新的经验回归检索方法后，OLCI IWV 测量的时空性能在站点尺度和每日尺度上都得到了改进。