![[image from MST radar]](mst.gif)
Colours are used to indicate the received power from back scatter, with purple as low power, through green, to red as high power.
By now, I hope that you will have some interest in estimating the height and condition of the tropopause. You can do this in several ways, but the most obvious and visual is to look at vertical radio reflection (back scatter) from an MST radar station. Here is an excerpt to illustrate this.
A small section of an MST radar image
Colours are used to indicate the received power from back scatter, with purple as low power, through green, to red as high power.
There are usually two bands of strong back scatter: the lowest 5 to 7 km, and one at 8 to 14 km which is close to the tropopause.
This second band is shown here as the distinct green band at around 13 km.
Follow the behaviour of this upper band, and I think you'll see that you get best NDT through that area when the band is high and well-defined (i.e. it appears solid, and contrasts well with weaker back scatter below it).
When the band is broken, ill-defined, and low, then you will find NDT harder to work over longer distances.
Remember, though, that the back scatter responsible for MST radar measurements is determined by a different physical mechanism from the forward scatter responsible for NDT propagation. So although this gives an indication of the structure of the troposphere, it is not such a reliable indicator of the prospects for forward scatter.
Last updated 2 Oct 1998
Howard Oakley
Mail howard@quercus.demon.co.uk