7. September 2016

HA­LO in the Caribbean – trop­i­cal cloud re­search

Clouds near Barbados
Clouds near Bar­ba­dos
Image 1/6, Credit: DLR (CC-BY 3.0)

Clouds near Barbados

Dur­ing the re­search flights from Bar­ba­dos with HA­LO, the re­searchers will be in­ter­est­ed in the prop­er­ties and for­ma­tion pro­cess­es of cu­mu­lus clouds in the trop­ics.
HA­LO on the tar­mac in Bar­ba­dos
Image 2/6, Credit: DLR (CC-BY 3.0)

HALO on the tarmac in Barbados

Sci­en­tists from var­i­ous Ger­man re­search in­sti­tu­tions are con­duct­ing joint cli­mate re­search with the HA­LO re­search air­craft.
HALO cabin with scientific instruments
HA­LO cab­in with sci­en­tif­ic in­stru­ments
Image 3/6, Credit: DLR (CC-BY 3.0)

HALO cabin with scientific instruments

In most of the cab­in area of the HA­LO re­search air­craft, sci­en­tif­ic in­stru­ments are in­stalled. Of par­tic­u­lar note are the air in­takes in the roof of the cab­in.
HA­LO with bel­ly pod
Image 4/6, Credit: DLR (CC-BY 3.0)

HALO with belly pod

Eas­i­ly vis­i­ble in the im­age is the bel­ly pod, where ad­di­tion­al sci­en­tif­ic in­stru­ments are in­stalled.
High above the clouds
High above the clouds
Image 5/6, Credit: DLR (CC-BY 3.0)

High above the clouds

HA­LO can reach a max­i­mum al­ti­tude of 15.5 kilo­me­tres (51,000 feet).
HALO: High Altitude and Long Range Research Aircraft
HA­LO: High Al­ti­tude and Long Range Re­search Air­craft
Image 6/6, Credit: DLR (CC-BY 3.0)

HALO: High Altitude and Long Range Research Aircraft

The HA­LO re­search air­craft is unique in the world and is open­ing up new di­men­sions in the study of the at­mo­sphere. The com­bi­na­tion of range, cruis­ing al­ti­tude, pay­load and com­pre­hen­sive in­stru­men­ta­tion make the air­craft a glob­al­ly unique re­search plat­form.

What effects do tropical clouds have on our climate? Do they warm up or cool down the atmosphere? What factors do they influence? Even the latest models do not fully understand the effects of these climate-influencing 'clouds'. Scientists from the German Aerospace Center (Deutsches Zentrums für Luft- und Raumfahrt; DLR), together with partners from other research institutions, went to the Caribbean to investigate these questions. On 8 August, the DLR-operated research aircraft HALO (High Altitude and Long Research Aircraft) took to the skies from Oberpfaffenhofen in Bavaria to travel some 7500 kilometres to tropical Barbados. This direct research and transfer flight forms part of the EU­REC4A (Next generation Aircraft Remote-sensing for Validation) campaign. The Max Planck In­sti­tute for Me­te­o­rol­o­gy is responsible for the scientific management of the measurement flights.

Improved forecasts for a better climate

The aim of the campaign is to improve our understanding of the relationship between clouds, air circulation and the climate over the tropical ocean. More detailed information about the nature of clouds and their constituents will then lead to the validation and refinement of climate models. This is a complex field of study because the clouds that form in the tradewind region cover a large area of the Earth, and therefore have a significant influence on just how much the atmosphere is able to mitigate global warming through changes in cloud formation.

Research into cloud formation

Studies carried out south east of Barbados allowed scientists to test their hypotheses related to the convection processes of clouds. In meteorology, convection is defined as the process during which warm air rises, which leads to the formation of cumulus clouds in the sky. These kinds of clouds have a sharp outer boundary and often take the shape of piles or heaps.

Atmospheric researchers are investigating which mechanisms on the ground, as well as in the atmosphere, affect air circulation. At the same time, they are looking into the type of clouds these processes lead to. Their research will also examine the size of ice particles and water droplets within the clouds. The ice phase, as it is known, is of particular interest when studying the life-cycle of cumulus clouds, as it is believed to have a great impact on the climate. This is because high altitude ice clouds have a different effect on the climate than those found at lower altitudes and that cover a wider area.

The focus here will be on the effect that a cooling atmosphere has on air layers, which in the tropics develop into cloud clusters. HALO will be used here to drop numerous dropsondes. "Due to the considerable number of dropsondes used during our flights, accurate communication with the checkpoints on the ground was vital," says Steffen Gemsa, a DLR research pilot. "Being able to fly at relatively low altitudes – in other words below that of regular passenger planes, as well as in areas where there is a low volume of traffic – made our work in the skies much easier."

Parachute research

Dropsondes are measuring devices that are dropped from an aircraft and fall to the ground by parachute. During their descent, they acquire data on pressure, temperature and humidity in the air. This enables data to be gathered over a large area. In particular, data on the vertical movement of convection, as well as the heat and humidity budget, can be recorded in an area stretching hundreds of kilometres for several hours.

The measurement flights with HALO are being conducted in conjunction with stationary measurements being carried out at the Cloud Observatory of the The Cloud Ob­ser­va­to­ry on Bar­ba­dos, in addition to data gathered from satellites. The remote sensing device on HALO also validates data obtained by the Cloudsat, Calipso, Meghatropique and GPM satellites during its research flights.

Additional expertise

The flight path is determined on a daily basis. Scientists from the DLR Institute of Atmospheric Physics and the pilots and experts from the DLR Flight Op­er­a­tions (FB) analyse the satellite images and current weather data, continuously on the lookout for areas where cloud clusters are developing. A total of 80 flight hours will enable them to study their own research questions, as well as support their scientific partners with their research. "Our scientific focus is on the issues surrounding how cloud properties differ during dry and wet periods, and how the presence of aerosols affects cloud formation and their properties," explains Silke Groß from the DLR Institute of Atmospheric Physics in Oberpfaffenhofen. "We will also measure the vertical distribution of the water vapour content, as well as the properties of the aerosol and clouds along the flight path."

Two manoeuvres above the clouds

HALO, the most modern of DLR's 13 research aircraft, is performing two different manoeuvres. First, to investigate emerging cloud clusters, the pilots will circle around the cloud tower in order to gather as much data as possible during its formation. These flights will be carried out at an altitude of around 10 kilometres, in the troposphere, which is the lowest layer of the Earth's atmosphere. "One of our aims is to measure the vertical velocity of cloud towers for the first time," Principal Investigator of the mission Bjorn Stevens of MPI for Meteorology in Hamburg, explains. "Based on the initial analysis of the data, we are confident that the measurements were taken successfully, and that we now have additional important pieces of the puzzle, which will enable us to understand the formation and development of clouds."

The second manoeuvre will enable scientists to measure the development of high altitude convection air masses over a large area. For this, HALO will fly through significantly higher layers of the atmosphere, on uniform, adjacent paths. Scientists are particularly interested in the altitude at which water droplets in clouds start to freeze. Radar and other methods will target the ice particles. Initial analyses indicate that the formation of ice starts at a much lower level in the troposphere than previously thought. Overall, these findings contribute to the development of more precise climate models and a better understanding of tropical cloud circulation.

About the project

The NARVAL II project is a joint project by the Max Planck Institute for Meteorology, the DLR Institute of Atmospheric Physics, and the Universities of Munich, Cologne, Hamburg and Leipzig. Research conducted as part of NARVAL II also serves as preparation for the experimental strategy for several international aircraft as part of greater field experiment within the French-German EU­REC4A initiative, which is planned for 2019.

About HALO

The HALO research aircraft is a joint initiative involving German environmental and climate research institutions. HALO is supported by grants from the Federal Ministry for Education and Research (BMBF), the German Research Association (DFG), the Helmholtz Association, the Max Planck Society (MPG), the Leibniz Association, the Free State of Bavaria, the Karlsruhe Institute of Technology (KIT), the German Research Centre for Geosciences in Potsdam (GFZ), the Jülich Research Centre and the German Aerospace Center (DLR).

Contact
  • Falk Dambowsky
    Ed­i­tor
    Ger­man Aerospace Cen­ter (DLR)
    Me­dia Re­la­tions
    Telephone: +49 2203 601-3959
    Fax: +49 2203 601-3249
    Linder Höhe
    51147 Cologne
    Contact
  • Steffen Gemsa
    Ger­man Aerospace Cen­ter (DLR)

    DLR Flight Ex­per­i­ments
    Telephone: +49 8153 28-3044
    Linder Höhe
    51147 Köln
    Contact
  • Dr Silke Groß
    Ger­man Aerospace Cen­ter (DLR)

    DLR In­sti­tute of At­mo­spher­ic Physics
    Telephone: +49 8153 28-2545
    Linder Höhe
    51147 Köln
    Contact
  • Prof. Dr. Björn Stevens
    Max Planck In­sti­tute for Me­te­o­rol­o­gy
    Telephone: +49 40 41173-422

    Contact
Images on this topic

Cookies help us to provide our services. By using our website you agree that we can use cookies. Read more about our Privacy Policy and visit the following link: Privacy Policy

Main menu