University of Cologne ceilometer profiles
Time-height sections of the data from our Vaisala ct25k ceilometer from April 16, 2010.
Bottom: color coded backscatter coefficient as a function of time and height. The higher
the backscatter coefficient the hazier is the air. White colors indicate clouds.
Top: detected cloud base heights (diamonds, tirangles and squares) and, if no cloud
but haze was detected, vertical visibility (+ signs).
On Friday evening the cloud cover opened at around 18UTC and an aerosol cloud between ~1500m
and 2500m became visible. This is probable part of the volcanic ash cloud from the
Eyjafjallajükull eruption on Iceland.
The instrument is mainly designed for the detection of cloud base heights
The detection of aerosol above ~4km is not possible. Nevertheless the occurance
of the cloud in our data fits to the model output for April 16 of the
Flexpart model at Nilu. It also fits to measurements with a much more
sensitive instrument at the KNMI in the Netherlands.
Further groups running much more sensitive instruments are the
Meteorological Institute Munich or the "Institut für Troposphärenforschung", Leipzig
This data comes from the
Institut für Geophysik und Meteorologie der Universität zu Köln
The same for April 17, 2010. No extra ordinary ash cloud visible.
The same for April 18, 2010. The aerosol layer is with 2km towards 24UTC unusual high
for this time of the year. But from this data we cannot conclude whether we see an ash cloud or not.
April 19, 2010. The unusual high extending aerosol layer is still visible until around 5:30UTC
when fog and a stratus cloud formed. This stratus remained until 12UTC with its base lifting up to 500m
and made the observation of aerosol above impossible. Blocked by the stratus in the morning but visible
in the afternoon the aerosol layer decreased during the day and reached with 1km normal heights at 24UTC.
The blue signals around 18UTC at 6km are cirrus clouds.
Actual ceilometer data