Atmospheric Motion Vectors (AMV's) have been derived from time-lapse fields of visible/infrared geostationary weather satellite imagery for nearly 30 years, and have become a fundamental component of operational meteorology. Corresponding Oceanic Motion Vectors (OMV's), similarly derived from time-lapse fields of ocean surface color and/or temperature, have seen only restricted use in a limited number of research applications. This is due to the limitations on available satellites and sensors, as well as obvious limitations due to cloud cover.

Recent new satellite launches, as well as other satellites that are scheduled for launch in the 2001/2002 time frame, have opened up new opportunities for deriving OMV's with improved accuracy and resolution, with particular application in coastal regions. Specifically, the Indian Space Research Organization's IRS-P4 satellite launched in May 1999, and NASA's EOS/Terra satellite launched in December 1999, both carry sensors that resolve coastal ocean color fields at spatial resolutions of 300 and 500 m, respectively. These two satellites will be joined by NASA's EOS/Aqua in late 2001, and the Japan Space Agency's ADEOS-2 in 2002; Aqua and ADEOS-2 will complement the spacecraft and sensors already operating, to derive OMV's.

The IRS-P4 carries the Ocean Color Mapper (OCM) instrument in a local noon orbit. OCM is virtually identical to the now familiar 8-channel Orbview-2/SeaWiFS instrument, with one important distinction: SeaWiFS spatial resolution is 1100 m (degrading to 1600 m at the edges of its 1400 km wide swath), while OCM spatial resolution is 300 m across its entire 1400 km swath.

The EOS/Terra and Aqua carry the MODIS sensor. Included in the sensors 36 spectral channels is a full suite of SeaWiFS-type ocean color channels at 1000 m resolution. But there are also three finer resolution channels that are suitable for detecting the strong color variations that often occur in coastal regions. These three channels are in the red (250 m), green (500 m) and blue (500 m).

Terra's sun-synchronous orbit time is 10:30AM, 1.5 hours prior to IRS-P4's noon orbit; Aqua will be launched into a 1:30PM orbit. The earth location accuracy for MODIS and OCM is equal to or better than the sensor resolution. Consequently, the lower bound on ocean feature movement is approximately 500 m over the 5000 s that separate these orbit times, corresponding to a surface flow speed of 10 cm/s. This is sufficient accuracy to be useful for mapping a broad variety of coastal current regimes.

Examples of OMV's from the California Current region, and from the relatively cloud-free Gulf of California, illustrate that this new combination of sensors has much promise as a valuable data source for coastal regions.