OMO is the first demo mission on the new HALO research Aircraft. It is scheduled to take place in summer 2013, to study the extra-tropical free troposphere (FT), between about 8-15 km altitude. This is a sensitive region of the atmosphere in terms of the climate response to chemical composition changes. Its upper section couples the stratosphere and troposphere. In the northern hemisphere the FT is substantially impacted by the long-distance transport of air pollution, supplied by episodic pollution uplift in convection and more gradual upward transfer in the warm conveyor belts of cyclonic disturbances. The removal rates of natural and anthropogenic gases as well as the formation of ozone are to a large degree controlled by oxidation reactions in which HOx radicals (OH+HO2) play a key role. Since only very few FT measurements of radicals and precursor gases have been performed, present assessments of atmospheric composition and climate change are strongly dependent on simulations with inadequately tested chemistry and general circulation models.
The HOhenpeißenberg Photochemistry Experiment (HOPE2012) campaign took place June - August 2012 at the Global Atmosphere Watch (GAW) station of the German Weather Service located 60 km south-west of Munich and approximately 20 km from the Alps at Hohenpeißenberg (988m, 47°48’ N, 11°0’ E). This campaign provided the first ambient air measurements of our newly built ROx – LIF instrument, thus investigating the ability of this instrument to measure ambient peroxy radicals. We measured OH and HO2 with a second LIF instrument. With this instrument, we were also able to measure atmospheric Stabilized Criegee Intermediates (SCIs) as a fraction of the total OH measured by a chemical subtraction method. This campaign allowed for extensive testing and characterization of SCI chemistry and further development of our chemical subtraction method. In addition, simultaneous side-by-side measurements were conducted with our two LIF instruments and a Chemical Ionization Mass Spectrometry (CIMS) instrument. Our data, together with supporting measurements, will be used with the constrained box model CAABA/MECCA to investigate the photochemistry budget in a rural mid-latitude environment.
DOMINO reloaded (2010)
Results of the DOMINO (Diel Oxidation Mechanism In relation to NitrogenOxides) campaign encouraged us to conduct additional measurements to extend our data base at the same site in Spain one year later.
We initiated this campaign (Diel Oxidation Mechanism In relation to NitrogenOxides) to study the sources and sinks of OH and HO2 in a complex environment in the planetary boundary layer. The chosen site in southern Spain is close to the sea on one side and has a national park dominated by pine and eucalyptus trees. In short distance to the site are two cities of which one is home of oil refineries. Depending on the wind direction we expected air masses with different finger prints of anthropogenic and biogenic trace gases to be transported to the measurement site.
HOOVER 2 (2007)
During the summer campaign a complementary data set was collected to compare with the fall observations of HOOVER 1 (HOx Over Europe) conducted in 2006. An additional focus was placed on convective transport and processing in thunderstorm clouds as well as the oxidation capacity in the Arctic during the long polar day. Very high OH mixing ratios were detected in the outflow of a convective system over central Germany, together with equally enhanced nitric oxides, indicative of enhanced photochemistry in the upper troposphere convective transport of HOx precursors.
HOOVER 1 (2006)
The aim of the HOOVER (HOx OVer Europe) campaigns was to study the seasonal and latitudinal trace gas distribution and its impact on the photochemistry in the free troposphere over Europe. A first campaign was conducted in fall 2006, a second one in summer 2007. The observations obtained in fall were used to compare with summer observation to identify seasonal changes of the oxidation capacity in the free troposphere.
In March 2007 we participated in the OOMPH campaign, which took place on the French science vessel Marion-Dufresne in the South Atlantic. Measurements of OH and HO2 (together called HOx), combined with photolysis frequencies and relevant trace gas concentration data also available for this campaign, allow to assess our present understanding of the photochemistry in remote marine areas, the oxidation of marine volatile organic compounds (VOCs), and its impact on aerosol formation and the global ozone budget.
Within the ACCENT frame of the "Quality Assurance/Quality Control (QA/QC)" a campaign was conducted at Forschungszentrum Jülich in July 2005 for intercomparison of OH/HO2 instruments at the atmosphere simulation chamber SAPHIR. The objectives were:
- Bring together the world-wide OH/HO2 radical measurement community.
- Perform a double-blind intercomparison in outdoor as well as under controlled conditions in the SAPHIR chamber
The GABRIEL (Guyanas Atmosphere-Biosphere exchange and Radicals Intensive Experiment with the Learjet) campaign in October 2005 was conducted as follow-up project of the 1998 LBA-CLAIRE experiment with an extended state-of-the-art scientific payload. The main purpose of GABRIEL was to observe and quantify detailed OH/HO2 formation and destruction chemistry in the atmosphere over the Amazonian rainforest during the long dry season as a function of the atmosphere-biosphere exchange. A secondary objective was to study the role of convective transport in the vertical distribution of primary and secondary gaseous species over the continental Amazon with respect to tropospheric chemistry and tracer budgets.