Assessment of Accuracy of Moderate-Resolution Imaging Spectroradiometer Sea Surface Temperature at High Latitudes Using Saildrone Data

• Published in: Remote Sensing
• Main Authors: Chong Jia, Peter J. Minnett, Malgorzata Szczodrak
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2024
• Subjects: MODIS; sea surface skin temperature; Saildrone; validation; Arctic; Science; Q; Pacific
• Online Access: https://doi.org/10.3390/rs16112008; https://doaj.org/article/1343d2b4f5914b20832e5ae2c87512b4

The infrared (IR) satellite remote sensing of sea surface skin temperature (SST skin ) is challenging in the northern high-latitude region, especially in the Arctic because of its extreme environmental conditions, and thus the accuracy of SST skin retrievals is questionable. Several Saildrone uncrewed surface vehicles were deployed at the Pacific side of the Arctic in 2019, and two of them, SD-1036 and SD-1037, were equipped with a pair of IR pyrometers on the deck, whose measurements have been shown to be useful in the derivation of SST skin with sufficient accuracy for scientific applications, providing an opportunity to validate satellite SST skin retrievals. This study aims to assess the accuracy of MODIS-retrieved SST skin from both Aqua and Terra satellites by comparisons with collocated Saildrone-derived SST skin data. The mean difference in SST skin from the SD-1036 and SD-1037 measurements is ~0.4 K, largely resulting from differences in the atmospheric conditions experienced by the two Saildrones. The performance of MODIS on Aqua and Terra in retrieving SST skin is comparable. Negative brightness temperature (BT) differences between 11 μm and 12 μm channels are identified as being physically based, but are removed from the analyses as they present anomalous conditions for which the atmospheric correction algorithm is not suited. Overall, the MODIS SST skin retrievals show negative mean biases, −0.234 K for Aqua and −0.295 K for Terra. The variations in the retrieval inaccuracies show an association with diurnal warming events in the upper ocean from long periods of sunlight in the Arctic. Also contributing to inaccuracies in the retrieval is the surface emissivity effect in BT differences characterized by the Emissivity-introduced BT difference (EΔBT) index. This study demonstrates the characteristics of MODIS-retrieved SST skin in the Arctic, at least at the Pacific side, and underscores that more in situ SST skin data at high latitudes are needed for further error identification and algorithm ...