JASMES Ocean Surface Current (OSC) (Daily,0.06deg)

Product Summary

Ocean surface current vectors can be estimated by the maximum cross-correlation (MCC) method using multiple observation images with a time lag of sea-surface temperature (SST)[1],[2],[3] or geostational ocean color images.[4],[5] The MCC method using the optical imagers cannot be used in cloudy areas; however, it can produce the surface current vectors with higher spatial resolution and a two-dimensional snapshot. We applied MCC using image pairs of SGLI boarded on GCOM-C, which takes images by 250-m spatial resolution at around 10:30 am local time, and Ocean and Land Color Imager (OLCI) on Sentinel-3A and Sentinel-3B, which by 300-m resolution at around 10:00 am.
The ocean surface current vectors are derived as following processes (1)-(5) [6].
(1)SGLI and OLCI ocean color data (Linear Combination Index of Rrs) are mapped to the same 250-m resolution, equal latitude-longitude grids.
(2)Outliers are excluded, and image noise is reduced by taking the average over a +/-2 pixel window.
(3)The pixel lag of MCC between sub-areas (square of +/-30 pixels) of OLCI and SGLI images are searched along with zonal and meridional directions over a 25-pixel interval (the grid interval of the output vectors).
(4)The current velocity and direction are estimated by the time difference of the two images and the zonal and meridional pixel lag of MCC excluding the case of MCC<0.4.
(5)Vectors are masked as an error when half or more numbers of the neighboring grid (four samples out of eight in the maximum case) have different values from the value of the target grid by >=50% and >=0.2 m/s (following [3]).
The SGLI LCI is calculated using VN04, VN06, and VN10, and OLCI LCI is calculated using the channels 04 (490 nm), 06 (560 nm), and 17 (865 nm) by Eqs. (2) and (3) following [7]:
LCI_SGLI = rmc(VN04) -1.4239 rmc(VN06) +0.4104 rmc(VN10), (2)
LCI_OLCI = rmc(04) -1.3822 rmc(06) +0.3699 rmc(17), (3)
where
rmc = (rT - rM) / T. (4)
The ocean surface current vectors estimated in the south of Japan islands on relatively fine days in 2020 were validated by comparing with six-hour current vector data from NOAA drifting buoys.[8] The root mean square difference between the surface current data of the buoy and the nearest estimated vectors within +/-12 hours was about 0.2 m/s.

Notice for usage and limitations:
The vector by MCC using 250 m resolution ocean color data needs to consider the transition of ocean color patterns that are not usually coincident with the velocity of the ocean surface layer, and the data is only available in the daytime in cloud-free areas and can be lacking for several weeks in the rainy season.

Reference:
[1] Kelly, K. A., and Strub P. T.: Comparison of velocity estimates from Advanced Very High Resolution Radiometer in the coastal transition zone, J. Geophys. Res., 97 (1992), pp. 9653-9668.
[2] Barton, I. J.: Ocean currents from successive satellite images: The reciprocal filtering technique, J. Atmos. Oceanic Technol., 19 (10) (2002), pp. 1677-1689.
[3] Kim, H-Y., Park, K-A., Kim, H-A., Chung, S-R., and Cheong, S-H: Retrievals of Sea Surface Current Vectors from Geostationary Satellite Data (Himawari-8/AHI), Asia-Pacific J Atmos Sci, 56 (2020), pp. 249-263. https://doi.org/10.1007/s13143-019-00163-4.
[4] Yang, H., Arnone, R., and Jolliff, J.: Estimating advective nearsurface currents from ocean color satellite images, Remote Sensing Environment, 158 (2015), pp. 1-14.
[5] Warren, M. A., Quartly, G. D., Shutler, J. D., Miller, P. I., and Yoshikawa, Y.: Estimation of ocean surface currents from maximum cross correlation applied to GOCI geostationary satellite remote sensing data over the Tsushima (Korea) Straits, J. Geophys. Res. Oceans, 121 (2016), pp. 6993-7009.
[6] Murakami, H.: "Atmosphere and ocean-surface observations by GCOM-C (SHIKISAI) Authors," Journal of Evolving Space Activities (2023) Vol. 1-65.
[7] Frouin, R., Deschamps, P., Gross-Colzy, L., Murakami, H., and Nakajima, T.: Retrieval of Chlorophyll-a Concentration via Linear Combination of ADEOS-II Global Imager data, Journal of Oceanography, 62 (3) (2006), pp. 331-337.
[8] Lumpkin, R., and Centurioni, L. (2019): Global Drifter Program quality-controlled 6-hour interpolated data from ocean surface drifting buoys. NOAA National Centers for Environmental Information. Dataset. https://doi.org/10.25921/7ntx-z961 (Accessed 3 January 2022).

Platform

GCOM-C, Sentinel-3A, B

Sensor

SGLI, OLCI

Coverage

Temporal Coverage

2021-08-01 to Present

Spatial Coverage

Bounding Rectangle
(50.0°, 150.0°, 24.0°, 123.0°)

Resolution

0.0625 deg

Location

• GEOGRAPHIC REGION > GLOBAL OCEAN