Mountain waves over the Alps

Filter by


EUMETSAT Users Twitter

RSS Feed

RSS Icon Image Library

High-level orographic cloud pattern occurred in the lee side of the Alps, gradually seen as a pronounced feature in the Convection RGB loop, along with the rising Sun.

Date & Time
10 November 2015 06:00–07:50 UTC
Convection RGB, Day Microphysics RGB, Natural Colour RGB, Airmass RGB

By Ivan Smiljanic (DHMZ)

During sunrise high level mountain waves became easier to distinguish from the rest of the clouds in the Meteosat Convection RGB imagery, animation from 10 November 06:00–07:50 UTC (MP4, 5 MB) and Figure 1.

Figure 1: Meteosat-10, 10 November 09:00 UTC
Convection RGB
Figure 2: Meteosat-10, 10 November 09:00 UTC
Day Microphysics RGB

The reason for that is the green component of the same RGB composite that includes a Sun reflection contribution in the 3.9 µm microphysical channel of SEVIRI instrument.

This also applies to the Day Microphysics RGB composite (Figure 2) which, even more so, has only the reflected component of the 3.9 µm channel (thermal Earth’s contribution extracted).

In the morning hours reflection from the very small ice particles, typical for high mountain waves, becomes gradually stronger. Reflection from the rest of the ice clouds naturally becomes gradually higher as well, but small ice particles always reflect much more.

Figure 3: Meteosat-10, 10 November 09:00 UTC
Airmass RGB
Figure 4: Meteosat-10, 10 November 09:00 UTC
Natural Colour RGB

From the Airmass RGB image (Figure 3) over the whole of Europe one could deduce the presence of the high-level north-westerly flow over the eastern Alps. This flow is responsible for the formation of observed wave cloud on the lee side of the mountains. This cloud looks very bright white in this RGB composite.

When we compare the different RGB combinations (Figure 1–4) it is obvious that the best contrast for wave clouds is given with the Convection RGB.

Previous case study

High-level mountain wave cloud over Pyrenees (2 July 2015)

We use essential cookies to ensure that we give you the best experience on our website. To analyse website traffic we also use third-party performance cookies. If you are ok with the use of essential as well as non-essential cookies, please select Accept & Continue. Instructions on how to prevent the use of non-essential cookies are available under our Terms Of Use, or simply select Decline Cookies.