This very
complex RGB composite is
available during day and night. It combines the following three MSG features:
the WV6.2 - WV7.3 Brightness Temperature Difference (BTD) on red, the IR9.7 -
IR10.8 BTD on green and the inverted WV6.2 channel on blue. All three features
are strongly related to airmass characteristics in cloud-free areas and to the
height of clouds in cloudy areas. The WV6.2 channel shows the horizontal
distribution of Upper Tropospheric Humidity. Typical features seen on the WV6.2
images include dry intrusions, deformation zones and jet streaks. The WV6.2 -
WV7.3 BTD, which depends on the temperature and humidity profile, shows the
distribution of moisture in the troposphere. Finally, the IR9.7 - IR10.8 BTD is
related to the total ozone concentration and thus to the height of the
tropopause.
Note: You can always click on the to bring up the RGB-key.
18 September 2007, 03 UTC
In the sequence a stripe of reddish colour is seen behind the cold front.
According to the MSG
Interpretation guide reddish colours stand for dry descending stratospheric
air related to an advection jet. In this case it is the jet stream flowing next to the rear side of the frontal cloud band.
These regions also correspond very well with the maxima in the Potential Vorticity field or the PV anomalies.
Very high convective cells, in bright white colour, are
seen over Slovenia, north Italy and
also over south Germany.
18 September 2007, 06 UTC
Cold airmass with low tropopause and large PV values, shown by bluish colours, propagates to
the south behind the frontal cloud band. Notice also the red area
wrapped around the low developing south-west of Portugal.
18 September 2007, 09 UTC
The jet with high PV flows across
western Europe. Cold airmass, characterized by bluish colour, is seen over the Scandinavia and a bit
further south. The red area west of Portugal gets more intense, meaning
that the cyclogenesis is taking place. Convective cells ahead the
frontal cloud band are clearly seen.
18 September 2007, 12 UTC
Red stripe over western Europe gets
even more intense and the convection starts also within the frontal
cloud band to the right of the red area.
