New analytical system for monitoring ocean conditions especially the sea surface temperature, with the aid of the remote sensing products of Himawari.

Abstract

We have used the remote sensing products for sea surface temperature （SST） provided by the artificial satellites to monitor SST and to perceive ocean currents around Japan, as well as to publish the Quick Bulletin of Ocean Conditions. In September 2022, we changed the method from using the SST observed by NOAA and MetOp to using the SST observed by Himawari-8. We had directly received the signals of SST data observed by NOAA and MetOp using an analytical system with parabolic antenna. We replaced that with the new system witch receives SST data observed by Himawari-8 provided by the Japan Aerospace Exploration Agency （JAXA） via an internet site. The replacement could reduce cost and workload for maintenance. In this report, we describe the outline of our new system for monitoring SST and the characteristic of the new SST images. The new system receives the SST products observed by Himawari-8 from JAXA. The observation interval of Himawari-8 is every 10 minutes. The high frequency observation could reduce data blanks in a one-day composite image caused by cloud coverages in comparison with the previous products. The daily average value was selected for composite SST images in order to avoid improbable SST patterns resulting from the comparison with the daily maximum and minimum values. To assure the accuracy of the new SST images, we compared the new product against SST datasets based on the result of direct observation in several cases. The anomaly between new images and the CTD dataset of the Chiba light beacon in the Tokyo bay is approximately ±0.6℃ among the 10－28℃ in SST. In other case, the anomaly compared with the SST datasets of Kuroshio-Bokujo buoys off the coast of Shikoku is approximately －1.1℃ and mostly accorded at 17℃ and 29℃ of buoy-observed temperature, respectively. When comparing the water temperature data of NOAA and Metop with the water temperature data of Himawari-8, it was found that Himawari-8 was approximately 0.7 ℃ lower at water temperature 28℃, and approximately 0.4℃ at water temperature 5℃.