Radiation – Aerosol – Cloud Experiment in the Arctic Circle (RACEPAC)

Regions: Inuvialuit Settlement Region

Tags: physical sciences, atmospheric sciences, meteorology, aerosols, cloud

Principal Investigator: Ehrlich, André (1)
Licence Number: 15406
Organization: University of Leipzig
Licensed Year(s): 2014
Issued: Jan 31, 2014
Project Team: André Ehrlich (Principle Investigator, University of Leipzig, Germany), Johannes Schneider (Researcher, Max Planck Institute for Chemistry Mainz, Germany), Ralf Weigelt (Researcher, Institute for Atmospheric Physics, Mainz, Germany), Martina Krämer (Researcher, Forschungszentrum Jülich, Germany), Martin Schnaiter (Researcher, Karlsruhe Institute for Technology, Germany), Olivier Jourdan (Researcher, Laboratoire de Météorologie Physique (LaMP), France), Andreas Herber (Researcher, Alfred Wegener Institute for Polar and Marine Research, Germany), Roland Neuber (Researcher, Alfred Wegener Institute for Polar and Marine Research, Germany)

Objective(s): To improve the understanding of the cloud-related processes in the Arctic atmosphere and knowledge on aerosol properties which act as cloud nuclei is essential as the aerosol particles may change the characteristics of the clouds.

Project Description: These research activities combine investigations of clouds and atmospheric aerosol in the Beaufort Sea. The main aim of the cloud studies is to improve the understanding of the cloud-related processes in the Arctic atmosphere and to use these measurements to improve the performance of regional and global climate models of the Arctic. To understand cloud processes knowledge on aerosol properties which act as cloud nuclei is essential as the aerosol particles may change the characteristics of the clouds. These cloud-aerosol interactions will be studies and aerosol properties characterized.

The research team will perform airborne measurements with two aircrafts, the Polar 5 and Polar 6 owned by Alfred-Wegener Institute for Polar and Marine Research, Germany, and operated by Kenn Borek Air, Canada. The research team has defined two different missions, one with respect to cloud studies (cloud mission) and one with the focus to aerosol measurements in clear sky conditions (clear sky mission).

Cloud Mission: The target of the cloud studies will be low-level stratiform clouds (1000–6000 ft / 300–2000 m). The scientific objective is to observe (from above) and probe (from inside) those clouds. To this purpose, two kinds of flight strategies are required, one for “remote sensing” using solar radiation (observing) and one for “in-situ probing” of the cloud particles (concentration, size, phase, shape), respectively. Having two aircrafts each aircraft is dedicated for one of the two flight strategies, Polar 5 doing “remote sensing” and Polar 6 “in-situ probing”. Synchronizing and collocating the flight tracks of both aircrafts allows the research team to simultaneously sample inside the clouds and do the remote sensing, which is a key improvement in the research. Both kinds of strategies are briefly described below:

a) Remote-sensing flights (Polar 5) will be typically performed at a constant altitude above the cloud top (typically near the maximum aircraft altitude; 10,000 ft / 3,000 m). These legs are straight lines up to 100 km long. Short cross track legs will be inserted to launch drop sondes and to keep the synchronization with Polar 6.

The drop sondes will be launched only at 10,000 ft (3,000 m) and only over uninhabited areas to determine the vertical structure of the atmosphere. The remote sensing instrumentation for the observations (SMART-Albedometer, AISA Eagle, Sun Photometer, AMALi) is almost entirely located inside the under-floor compartments of the aircraft, which are closed by roller doors when not operated. Only the sun photometer and parts of the SMART-Albedometer are mounted on the roof of the aircraft: While the sun photometer is installed within the large glass dome, the SMART-Albedometer optical inlets are mounted at the view port close to the door. AMALi, the lidar system, can also be configured to measure in zenith direction, for which a second viewport on top of the fuselage is used. The lidar system will be operated in nadir direction only above altitudes of 9,000 ft. In zenith configuration it will be operated at all altitudes.

b) In-situ flights (Polar 6) typically consist of ramps (ascending and descending, at a rate of 500 to 1000 ft per minute) through the cloud layer as well as horizontal sections just above the cloud top (to remove aircraft icing) and just below the cloud bottom (background aerosol characterization). The instrumentation used during these legs will be installed in standard pedestal-mounted stinger (PMS) canisters under the wings. The aerosol characterization is partly realized by systems (ALABAMA, IAGOS) that suck air through an aerosol inlet fixed on the top of the aircraft.

For the typical cloud study, the Polar 5 and 6 aircrafts will take off from Inuvik airport and fly at high altitude (approx. 10,000 ft / 3,000 m) into the target area and perform the described science flight legs there. Polar 6 will additionally fly vertical profiles up to 10,000 ft to monitor the vertical distribution of aerosol particles. These continuous accents and step wise descends will be performed at the beginning and end of each flight. After each research mission, the aircrafts will fly back to Inuvik at high altitudes (up to 10,000 ft / 3,000 m) measuring solar radiation and aerosols.

Clear Sky Mission: In cloud free conditions the focus is on characterizing atmospheric aerosol. Again, the research team will combine the remote sensing by Polar 5 and in-situ sampling by Polar 6. Polar 5 will take off earlier from Inuvik and try to detect aerosol layers by remote sensing of the sun photometer and the AMALi lidar system (upward looking configuration). The flight altitude is low (500 ft) to have most of the atmosphere above and in the measuring range of AMALi. Additionally, these legs will be used to measure albedo of sea ice and monitor sea ice concentration. To launch radio sondes during these flights short profiles up to 10,000 ft will be inserted. Polar 6 will follow Polar 5 half an hour later and directly fly into the interesting areas and altitudes identified by Polar 5. The sampling will mostly be realized by vertical profiles. To cover aerosol particles transported from long distances in higher altitudes the research team will increase the maximum flight height to 15,000 ft for short sequences (<30min). After each research mission, the aircrafts will fly back to Inuvik at high altitudes (up to 10,000 ft / 3,000 m) measuring solar radiation and aerosols.

For one flight it is planned to compare the airborne aerosol measurements with ground based instruments located in Tuktoyaktuk. Parallel to the research project proposed here, the Max Planck Institute for Chemistry, Mainz, Germany is organizing ground based aerosol measurements in Tuktoyaktuk for the same period of time. For the comparison Polar 6 will fly vertical profiles close to the ground station. Additionally, the research team has planned a short stop at the airport of Tuktoyaktuk to have a direct comparison of the instruments.

In general, the aircraft will not fly at low altitudes until it is safely away from the coast of the mainland and Banks Island. No landing of the aircraft will take place during each mission, except of one. The aircraft will avoid the floe edge and bird/wildlife sanctuaries. The crew on board the aircraft will look for marine mammals on the sea ice, and if encountered during low altitude flight, the aircraft will change course to avoid them. If the proposed flight plan is not suitable, the crew will take a different route based on the recommendation of the local Hunters and Trappers Committees.

The Polar 5 research aircraft is a Canadian Basler BT–67 (call sign C–GAWI) and will be equipped with the following instruments: SMART-Albedometer (measurement of the solar radiation spectrum), AISA Eagle (hyperspectral camera), broadband sensors for solar and infrared radiation, AMALi lidar system, AIMMS-20 (winds and turbulence), sun photometer (optical thickness of aerosol column), digital video cameras, and meteorological sensors.

The Polar 6 research aircraft is a Canadian Basler BT–67 (call sign C–GHGF) and will be equipped with the following instruments: cloud-particle probes NIXE/CCP/ (cloud particle size distribution), Small Ice Detector SID-3 (characterization of ice particles in clouds), precipitation imaging probe PIP (drizzle droplets, snow sampling), holographic cloud particle detection, Polar Nephelometer, AMS (aerosol particles mass spectrometer), IAGOS (aerosol size distribution), CO, CO2 and soot sampler, AIMMS-20 (winds and turbulence), broadband sensors for solar and infrared radiation, digital video cameras, and meteorological sensors.

Climate change and sea ice change affects all that live in the north. The aim of this project is to improve understanding of the physical processes in Arctic clouds and their contribution to the current changes in the polar environment, and thereby reducing uncertainties in regional and global model simulations important for future weather and climate prediction
A summary report will be submitted to the Aurora Research Institute, Inuvik.






The fieldwork for this study will be conducted from April 18, 2014 to May 23, 2014.