Flying 100,000 kilometers through the monsoon

Atmospheric researchers investigate the impact of the monsoon on air quality and climate change

Mainz, 17 July 2015

By aircraft from Cyprus to the Maldives and back. What sounds like a holiday in the sun will actually be hard work for scientists of the Max Planck Institute for Chemistry. End of July the scientists from Mainz, in a team of 65 colleagues, will start a 30-day research mission to investigate the Earth’s atmosphere with the new High-altitude Long-range HALO aircraft of the German Aerospace Center (DLR).

The HALO research aircraft is equipped with numerous inlets through which air samples get to the instruments inside. Picture: DLR
The HALO research aircraft is equipped with numerous inlets through which air samples get to the instruments inside. Picture: DLR

They will study how the self-cleaning capacity of the atmosphere is affected by the Asian monsoon. This self-cleaning property is central in cleaning the air from many pollutants. Short-lived, highly reactive oxidants chemically convert hydrocarbons, such as the greenhouse gas methane and emissions from industry and road traffic, making them more water soluble and thus allowing them to be removed by rain. Since air pollution in Asia is increasing drastically on a large scale, scientists suspect that this has a global impact on the atmospheric self-cleaning capacity and consequently on air quality and climate change.

“The monsoon rainfalls can wash out many soluble gases and aerosol particles from the atmosphere, however, we do not know how efficient these processes are,” says Jos Lelieveld, Director at the Max Planck Institute for Chemistry and principal investigator of the research mission. “Once we understand the chemical and transport processes of the polluted air masses in the Asian monsoon, we can improve predictions of air quality and climate change,” he adds.

The OMO team preparing the mission in Oberpfaffenhofen, Picture: Rolf Hofmann, MPIC
The OMO team preparing the mission in Oberpfaffenhofen, Picture: Rolf Hofmann, MPIC

In collaboration with colleagues from the Research Center Jülich, the German Aerospace Center, the Karlsruhe Institute for Technology and the universities of Bremen, Heidelberg, Leipzig and Wuppertal, the atmospheric chemists from Mainz have developed a comprehensive instrument payload for HALO, needed in this unique aircraft mission.

Following the name of a detergent, the researchers called their project “OMO”; in science, however, this is an abbreviation of “Oxidation Mechanism Observations”. In more than 120 flight hours with the HALO aircraft, they will cover about 100,000 kilometers in the atmosphere and examine the air downwind of the monsoon above Asia and the Middle East. HALO is a high-flying jet that was specially adjusted for atmospheric research, and is operated by the DLR.

From Cyprus to the Maldives and back

During a test flight Korbinian Hens (MPIC), Anke Roiger (DLR) and Markus Horstjann (University of Bremen) collect data from their instruments. Picture: Garlich Fischbeck (KIT)
During a test flight Korbinian Hens (MPIC), Anke Roiger (DLR) and Markus Horstjann (University of Bremen) collect data from their instruments. Picture: Garlich Fischbeck (KIT)

On July 21, 2015, the mission will start in Paphos, Cyprus, from where HALO will fly towards the Arabian Peninsula and the Arabian Sea. Then, the aircraft, crew and team will change course to the Maldives to analyze the atmosphere over the Indian Ocean and the Bay of Bengal. Subsequently, they will fly to Cyprus again to track the monsoon outflow for two weeks before the team and the aircraft return to Germany by the end of August.

HALO has a range of about 8,000 kilometers and can fly at an altitude of more than 15 kilometers, hence the researchers can cover flight tracks up to ten hours and also perform vertical profiles to characterize the air masses. In addition to ozone, nitrogen oxides, sulfur dioxides and volatile organic components, the researchers’ instruments also detect short-lived compounds such as hydroxyl radicals, which are important for the oxidation mechanism of the atmosphere. The hydroxyl radicals are also called the “detergent” of the atmosphere. Satellite data and model calculations will complement the aircraft measurements in the analyses after the flights.

Jos Lelieveld, who has also been a part-time professor at the Cyprus Institute in Nicosia since 2008, is very excited about the measurement campaign. “I am glad that we can finally start; our teams have put an enormous amount of time, energy and work into the preparations for the OMO mission. I am very grateful to them and our colleagues in Cyprus, who have provided excellent research conditions.”

Monsoon
The monsoon is a giant air flow which regularly forms over Asia in summer when air masses warm up more rapidly over land than over the ocean. The monsoon is the world largest weather system, which is particularly strong over South Asia. Its outflow reaches over the Middle East and the Mediterranean Sea and can even reach the stratosphere.

HALO
The HALO (High-Altitude and Long-Range) research aircraft is a German aircraft  dedicated to scientific research of the Earth’s atmosphere and was initiated jointly by the DLR and the Max Planck Society. It allows a previously unattained quality of measurements, particularly in the high-altitude layers between the troposphere and the stratosphere, which are difficult to get to with other measurement aircraft. The studies make an important contribution towards understanding ozone chemistry and the atmospheric transport of air pollutants.

OMO
The OMO aircraft measurement campaign addresses the “self‐cleaning capacity” of the atmosphere.  It focuses on the oxidation processes and air pollution chemistry downwind of South Asia during the summer monsoon.  The self‐cleaning mechanism converts natural and human‐made pollutants into soluble products that can be removed by rain. This is critical for air quality and climate change, both regionally and worldwide considering rapidly growing pollution emissions, especially in Asia.