NARVAL North: Cloud expedition successfully completed

7 February 2014, by Caroline Kieke

Photo: UHH/CEN/F. Ament

View from aircraft window: Cloud field.

The cloud expedition “NARVAL North” has provided important information about weather phenomena in North Atlantic low-pressure areas. The review of the collected data ...

The cloud expedition “NARVAL North” has provided important information about weather phenomena in North Atlantic low-pressure areas. The review of the collected data is fully under way. The new research aircraft HALO had been based in Iceland for measurement flights for almost three weeks. The Heads of Mission, Dr. Christian Klepp and Prof. Dr. Felix Ament of the Center for Earth System Research and Sustainability (CEN) were also on board.

“The results of the research flights have exceeded our expectations,” summarizes Christian Klepp. “Due to the unusual winter weather situation we had the chance to observe very different atmospheric phenomena.” During five flights, the flying cloud laboratory HALO examined low-pressure areas from the Labrador Sea – between Greenland and the Canadian peninsula Labrador – to the coast of Ireland. One of the flights in January led them into the storm front which had just covered the Northeast Region of the United States and Eastern Canada with frosty temperatures of up to minus 50 degrees Celsius and masses of snow.

The focus of the mission was on the back side of the cold fronts, still an unclear point in meteorology. If you read satellite data in the usual way, it suggests that there is hardly any precipitation in this area of cyclones. However, Klepp and other Hamburg meteorologists had developed an algorithm with the project HOAPS which reads the data in a different way. Accordingly, there are heavy rains, thunderstorms and snowfalls to the west of the cold fronts. Klepp was involved in setting up HOAPS and now finds his own views confirmed: “What we could observe from the aircraft was exactly what we had expected.”

“HALO has been constructed like a low-flying weather satellite,” Klepp explains the importance of the aircraft. Satellite sensors such as SSMIS cover the North Atlantic clouds from a height of 800 kilometers and thus can only provide data with a resolution of 50 kilometers per pixel. “Admittedly, these satellite data tell us that there is intensive weather at a specific place, but that is all. HALO, however, flies at a height of eight kilometers, having a considerably higher resolution of one kilometer on the ground,” underlines Klepp. Data of the weather satellite Cloudsat which are also being incorporated into the research project have a similar high resolution, rendering them a significant source. The satellites follow their tracks undeviatingly, in contrast to HALO. “With the research aircraft we could exactly head for the places which were of interest for us,” said Klepp.

The new data set is completed by a total of 47 dropsondes which the research team dropped into phenomena such as thunderheads or cloud-free areas. The sondes are small, mobile measuring stations which sink slowly to the earth on parachutes, determining a vertical profile of the atmosphere.

Now, together with their partners at the Max Planck Institute for Meteorology, at the universities of Cologne, Heidelberg, Leipzig and the German Aerospace Center (DLR), the researchers at the CEN have started analyzing the raw data. They are presenting their first results, among other places, at the annual conference of the professional association “European Geosciences Union” in Vienna in April.

The new aircraft, equipped with a large amount of advanced technology, is a joint initiative of German environmental and climate research institutions, operated by the German Aerospace Center (DLR). The so-called belly pod is the scientific core of the aircraft. The pod is attached under the aircraft fuselage, containing measuring instruments for the recording of clouds, precipitation, humidity and fine particles (aerosols).

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