What are the STA products?

The STA products are the albedo at the Top of the Atmosphere, i.e the ratio between the reflected solar radiation and the incoming solar radiation.

Why do we need to compute the STA products?

The STA products are internal products needed to compute the surface radiation products.

How to compute the STA products?

The STA products are computed either from the GERB data or from the GERB-like ones.
The GERB-like data are simulated GERB data obtained from a emperical regression applied to the data coming from the METEOSAT imager.
For each pixel of the GERB or GERB-like image, we estimate the incoming radiation considering a fix value of the TSI (here 1366 W/m^2), the position of the Sun (i.e. the solar zenithal angle) and its distance to the Earth. The formula is given in the TIS page. Once we have computed the incoming solar (IS) radiation, we are able to estimate the albedo by simply dividing the solar flux given in the GERB or GERB-like files by the IS.

What kind of STA data do we get from the CM SAF?

We process two STA images every 15 minutes (see examples below). These images are projected on the METEOSAT grid.
But as mentioned above, the STA products are internal products, they are not available for a public usage.

STA images

computed with GERB at 14:15 on the 9th August 2007		computed with GERB-like at 14:15 on the 9th August 2007