1. November 2017
Climate research

Mea­sur­ing the mix­ture of green­house gas­es over the At­lantic

The HALO research aircraft
The HA­LO re­search air­craft
Image 1/4, Credit: DLR/Andreas Minikin (CC-BY 3.0)

The HALO research aircraft

The HA­LO (High Al­ti­tude and Long Range Air­craft) re­search air­craft is char­ac­terised by its un­usu­al range and fly­ing al­ti­tude.
The HA­LO re­search air­craft at Shan­non Air­port in Ire­land
Image 2/4, Credit: DLR/Andreas Fix (CC-BY 3.0).

The HALO research aircraft at Shannon Airport in Ireland

In Oc­to­ber 2017, the HA­LO re­search air­craft flew from Shan­non Air­port in Ire­land over the At­lantic a to­tal of 17 times.
A view of ice clouds during the flight
A view of ice clouds dur­ing the flight
Image 3/4, Credit: DLR/Andreas Marsing (CC-BY 3.0)

A view of ice clouds during the flight

Ice clouds may pos­si­bly af­fect the ex­change pro­cess­es be­tween the tro­po­sphere and the strato­sphere.
Li­dar mea­sure­ment de­vice on board HA­LO
Image 4/4, Credit: DLR/Christiane Voigt (CC-BY 3.0).

Lidar measurement device on board HALO

The laser-based Li­dar in­stru­ment on HA­LO mea­sures the dis­tri­bu­tion of the wa­ter vapour and ozone green­house gas­es in the at­mo­sphere in great de­tail.
  • The HALO research aircraft measures the exchange of air masses between the troposphere and stratosphere
  • Trace gases from Asia and America are transported to Europe via the intercontinental jet stream
  • Changes in trace gases at the boundary between the troposphere and the stratosphere significantly affect our climate
  • Focus: Climate research, aeronautics

In October 2017, the HALO research aircraft measured the transport and mixing of greenhouse gases in the upper troposphere and lower stratosphere during measurement flights over the Atlantic starting from Shannon in Ireland. The measurement campaign is providing new knowledge regarding the origin, distribution and lifetime of trace gases at the climate-sensitive interface between these atmospheric layers. The WISE (Wave-driven ISentropic Exchange) national joint project managed by the Jülich Re­search Cen­tre and the University of Mainz, in which the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) is involved, will allow today's climate models to be defined more accurately.

"Tropical storms and hurricanes over the West Atlantic, weather fronts and the Asian monsoon provide very effective transportation of climate-relevant trace gases from the ground to higher atmospheric layers," explains Peter Hoor from the University of Mainz, one of the campaign's coordinators. "Air masses enriched with water vapour and other trace substances are then transported to Europe via the so-called jet stream and mixed so that we can also measure the effects of these weather phenomena in Europe," adds Christiane Voigt from the DLR In­sti­tute of At­mo­spher­ic Physics. "Through these measurements, we now have a much clearer picture of how these trace gases are distributed across the northern Atlantic and how clouds affect the stability of the atmospheric layers and thus the distribution of trace gases," Voigt continues.

For these measurements, the DLR-operated HALO (High Altitude and Long Range Aircraft) research aircraft flew a total of 17 times over the Atlantic. "The flights generally lasted between nine and 10 hours and went far out over the ocean," says Andreas Minikin, explaining the DLR Flight Op­er­a­tions (FB). "At an altitude of 13 to 14 kilometres, and in close agreement with air-traffic control, HALO generally flew above transatlantic air traffic." The HALO research aircraft is characterised by its unusual range and altitude.

Trace gases heat cold zones

The current measurement campaign confirmed the findings of the Jülich coordinator of the research campaign, Martin Riese, namely that changes in the concentration of the greenhouse gases water vapour and ozone in the relatively cold area of the atmosphere between about five and 20 kilometres above sea level have a particularly strong effect on the temperature on the ground. At the very cold interface between the troposphere and the higher stratosphere in particular, changes in trace gases have a significant effect on our climate.

Using the Differential Absorption Lidar (DIAL), developed by DLR, it has been possible for the first time to simultaneously measure water vapour and ozone, both important greenhouse gases, with a very high degree of accuracy and wide coverage. Furthermore, these measurements also provide information on the properties of high ice clouds and their influence on the exchange process in the upper troposphere and lower stratosphere.

The observation of nitrogen oxides in this boundary region is also of great interest in understanding the dynamics of the exchange processes between the atmospheric layers. "We have been able to measure the concentration of reactive nitrogen compounds in the atmosphere with very high accuracy for over 20 years," explains the atmospheric researcher Helmut Ziereis from the DLR Institute of Atmospheric Physics. "We upgraded this instrument again for HALO." The atmospheric concentration of nitrogen oxides is determined by a number of different sources. In addition to lightning and aircraft emissions, the stratosphere itself is the largest local source of long-lasting nitrogen oxide compounds in the upper troposphere and lower stratosphere. Added to this is, of course, the nitrogen oxide transported upwards from the ground. This is why the measurement of nitrogen oxides is particularly suitable as a marker for characterising the exchange of air masses between the troposphere and stratosphere.

The distribution of trace gases over Europe changes significantly through the intercontinental transport of air masses from Asia and America. To detect air from Asian or American regions, researchers used the AIMS mass spectrometer. This measuring instrument can be used to identify very low concentrations of sulphur compounds and other acidic trace substances, in order to infer the origin of the air. "We would like to find out which meteorological situations have a strong influence on the composition of air masses over Europe, and which processes are reinforced by the intermixing of air masses," adds Christiane Voigt. Only by mixing can the composition of the air in the climate-sensitive upper troposphere and lower stratosphere be changed permanently. "In addition, we want to investigate the influence of ice clouds on this atmospheric layer," continues Voigt. Earlier measurement campaigns using HALO have shown that ice clouds directly alter the radiation balance of the upper troposphere and lower stratosphere, and thus the climate. The WISE scientists are now additionally investigating the extent to which the ice clouds can also change transport and mixing in this climate-sensitive atmospheric layer.

The partners

In addition to the Jülich Research Centre and the University of Mainz, the partners in the WISE (Wave-driven ISentropic Exchange) joint project include the German Aerospace Center (DLR), the Karlsruhe Institute of Technology, the Universities of Heidelberg, Frankfurt and Wuppertal, as well as the National Metrology Institute of Germany (PTB; Physikalisch-Technische Bundesanstalt). The scientific flights are supported by a team of around 90 people.

The HALO research aircraft is a joint initiative of German environmental and climate research institutions. HALO was procured with funds from the German Federal Ministry of Education and Research (BMBF), the Helmholtz Association and the Max Planck Society. HALO is operated by the German Research Foundation, the Max Planck Society (MPG), Jülich Research Center (FZJ), Karlsruhe Institute of Technology (KIT), the German Research Centre for Geosciences (Deutsches GeoForschungsZentrum; GFZ) in Potsdam and the Leibniz Institute of Tropospheric Research in Leipzig (TROPOS). DLR both owns and operates the aircraft.

  • Falk Dambowsky
    Ger­man Aerospace Cen­ter (DLR)

    DLR Cor­po­rate Com­mu­ni­ca­tions
    Telephone: +49 2203 601-3959
    Linder Höhe
    51147 Cologne
  • Prof. Dr. Christiane Voigt
    Head of De­part­ment
    Ger­man Aerospace Cen­ter (DLR)
    In­sti­tute of At­mo­spher­ic Physics
    Cloud Physics
    Münchener Straße 20
    82234 Oberpfaffenhofen
  • Andreas Minikin
    Ger­man Aerospace Cen­ter (DLR)
    Flight Ex­per­i­ments
    Lilienthalplatz 7
    38108 Braunschweig
  • Helmut Ziereis
    Ger­man Aerospace Cen­ter (DLR)
    In­sti­tute of At­mo­spher­ic Physics
    Telephone: +49 8153 28-2542
    Münchener Straße 20
    82234 Oberpfaffenhofen

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