Check these simulations. http://hycom.org

Hi Arun,

There are several approaches possible depending on the penetration depth.

Penetration depth is a measure of how deep light or any electromagnetic radiation can penetrate into a material. It is defined as the depth at which the intensity of the radiation inside the material falls to 1/e (about 37%) of its original value at (or more properly, just beneath) the surface.

When electromagnetic radiation is incident on the surface of a material, it may be (partly) reflected from that surface and there will be a field containing energy transmitted into the matrix. This electromagnetic field interacts with material particles, solutes and water molecules in the coastal waters matrix. Depending on the nature of the material, the electromagnetic field might travel very far into the matrix, or may die out very quickly. For a given material, penetration depth will generally be a function of wavelength.

The depth to which sunlight penetrates into the water determines the transparency of a water body. Light penetration is dictated by the composition of the water. Water itself strongly absorbs light in the red region of the light spectrum, which is why clean, clear waters are blue. Other components in the water that impact its optical properties, include colored dissolved organic matter (CDOM), decaying organic matter, inorganic particulate matter, such as silt and clay, and phytoplankton.

Hence, a RED or NIR image will clearly show suspended particles in coastal waters, indicating when taken in a multi-temporal sequence, coastal water circulation.

To monitor the upwelling zones of oceans along the continental coasts of Africa and Europe, the thermal bands of SEVIRI with their 15 minute image grabs, are quite good to map the surface dynamics of ocean upwelling zones along continental coastlines.

This summarizes somewhat the applications especially with MSG-2 SEVIRI and its 15 minute observation interval, possible for coastal water circulation with optical and thermal remote sensing.

Cheers,

Frank

there are a number of satellites launched specifically to monitor the oceans. the OCM sensor used in Indian remote sensing satellites can be use for the purpose. Also the SMOS data can be used for the same.

Thank You all for the reply

You can use altimetry data to calculate surface geostrophic currents, there are different products and resolutions, depending on the application you need.

Frank, I think, that MSG SEVIRI has too coarse spatial resolution. So it is better to use multispectral low orbit satellites, in spite of worse temporal resolution.

About sounding - wavelengths of approximately 380-800 nm are able to penetrate to some depth and go back. Shorter waves are absorbed by dissolved organics, longer waves - by water itself.

Of course, information can be obtained from surface characteruistics pattern: temperature, floating material (ice, algae at the end of bloom). Some data may be obtained from SAR, but it is sensitive not only to oil spills, but also shows upwelling zones and even algae blooms, so it is necessary to support it by other satellite or airborne data.

Hi Aleksei,

You are partly right (as always). I agree that MSG SEVIRI, does not have an optimal spatial resolution. Moreover its spatial resolution is variable according to latitude North (and South). As you know its resolution at the equator is pretty good (a few km), when compared with the previous generation of METEOSAT's, but when viewing the high North or the low South (typically above 60°N or below 60° S) , spatial resolution degrades quite fast to non usefull dimensions, for surface waters. Hence for some of the Seas in the High North of Europe, Russia, Alaska, or Canada, it does not make much sense to use MSG-SEVERI, especially in winter.

Nonetheless, I think that between 60°North and South the big advantage of MSG SEVIRI is its high temporal resolution. Moreover a follow up METEOSAT third generation is in the making for launch within a few years with a 1 km resolution at the equator, as good as many polar orbiting sensors right now, but with the 15 min imaging interval.

To study the seaonal dynamics of the main oceanic and sea currents I think that this temporal resolution gives plenty of information, that might be as important as a one shot a day temporal resolution typical for the polar orbiting platform-sensor combinations. I agree that a multi-sensor approach is the best option to get to grips as well as possible with coastal water circulation as well as oceanic current dynamics and the activity and dynamics of upwelling and subduction zones, respectively along continental coasts, and close to the Earth's polar areas.

Lets' not forget either, that the mapping in 3D of oceanic dynamics at the global scale, still shows a lot of white area's, especially for the deep ocean currents, driven by the subduction of cold polar waters. On top of that we have the tropical waters which - with solar energy input - are the engines of many a sea current, which on their turn are the prime drivers for the dynamics of many a climate zone up North and down South.

Cheers,

Frank

Hi there,

If you really want the current, there are several approaches which are now being combined into the GlobCurrent project funded by ESA.

These include altimetry for the quasi-geostrophic part of the current, but the effective along-track resolution is around 100 km, not so good for coastal regions, despite many recent efforts.

Another possibility is to use the Doppler centroid from SAR data (see Chapron et al. JGR 2005 for details of the method): this is great for strong currents, otherwise you may need to average MANY SAR scenes to get a nice high resolution mean current. Good news is that the new products that are coming out of Sentinel 1 will be much more accurate than those of Envisat.

Obviously, there are also people deriving flow from the structure of images (MCC, optical flow) that can use any SST or color measurements..