Oct 232014

In July this year ATMOS group attended the 14th Conference on Cloud Physics and 14th Conference on Atmospheric Radiation which were held together in Boston. The conference is organised by the American Meteorological Society every 3 years. It is one of the biggest conferences in Cloud Physics and Radiation field.

We were presenting two posters:

  1. How Can We Use Lidar And Radar To Monitor Aerosol-Cloud Interaction? presented by Karolina Sarna
  2. The satellite observation of drizzle in Stratocumulus clouds presented by Igor Stepanov

If you are interested in the recordings from the Conference or Extended Abstracts, have a look here:



Jun 272013











On Wednesday we had an atmosphere observations day. Our colleagues from Met Office Iceland, Richard and Hermann, have demonstrated a mobile X-band unit, used during the expected volcanic eruptions in Iceland. Students have deployed the radar and launched a radiosonde from a mobile launcher. We visited our weather stations to collect the data and 2 out of 8 were knocked out due to strong wind.

Nov 222010

  The title of this post is inspired by the inaugural speech of Prof. Herman Russchenberg which was given last april 1st, 2009 (In de Schaduw van een wolk). Behind this title arise the question of how clouds act on climate by impacting the Earth radiation balance. This question is nowdays still strongly debated among the scientific community.

The picture below well illustrates the possible opacity of a cloud against solar radiations.

Dec 022009

Polar Mesospheric Clouds PMCs (also known as noctilucent clouds) exist at a height of about 76 to 85 kilometers. They are transient, upper atmospheric phenomena observed usually in the summer months at high latitudes (greater than 50 degrees)
 of both the Northern and Southern Hemispheres. PMCs are made of crystals of water ice formed at about −120 °C, although their formation mechanism are still not really understood nowadays. For more information, I let you refer to the wikipedia website : http://en.wikipedia.org/wiki/Noctilucent_cloud.

This image was acquired at an altitude of just over 200 miles in the pre-dawn hours of July 22, 2008 as the International Space Station was passing over western Mongolia in central Asia (credit NASA).
PMCs have been increasing over the past 30 years… sign of climate changes?
Nov 262009

This week, we come back to a mountain region (Mont-blanc in the Alps) to present a typical orographic cloud: the altocumulus lenticularis (two in this image):

These lenticular clouds often appear in the lee of the mountains due to the presence of gravity waves produced by moist air flowing over the mountain crests.
Nov 192009

The below image is a GOES-12 infrared imagery showing the location of the intertropical Convergence zone (ITCZ – red line).

In this area, the air from the subtropical regions of both hemispheres converges, leading to strong upward motion up to 15 km and divergence uloft (part of Hadley circulation). This zone is often associated with well developped cumulonimbus clouds with great vertical extension and thunderstorms. Many of the world’s rainforest are associated with these climatological low pressure system.

Nov 092009

Sometimes clouds are produced in an unusual manner….

Such cloud is most probably composed of water droplets created by the sudden drop of air pressure around the rocket

(1-X Rocket Lifts Off from NASA)

Aug 242009

  So I will start with a first picture from Australia (credit Mick Petroff).



Explanation: What causes these long, strange clouds? No one is sure. A rare type of cloud known as a Morning Glory Cloud can stretch up to 1000 km long and occur up to 2 km high. Although similar roll clouds have been seen at specific places across the world, the ones over Burketown, Australia occur predicably every spring. Long, horizontal, circulating tubes of air might form when flowing, moist, cooling air encounters an inversion layer, an atmospheric layer where air temperature atypically increases with height. These tubes and surrounding air could cause dangerous tubulences for airplanes when clear.