Ph.D. Physics, University of Heidelberg, Germany
Chemistry and Biochemistry
Rainer’s general interest is the study of atmospheric chemistry in air quality and climate science, using a combination of in-situ and remote sensing measurement techniques, which he and his group are developing and deploying in polluted urban and pristine atmospheric environments from ships, research aircrafts, and autonomous ground-based networks, and in simulation chamber experiments to develop and test the mechanistic understanding represented in atmospheric models used to manage air resources and climate.
Current Research: Airborne Observations of Reactive Trace Gases in the Free Troposphere
Oceans cover 70 percent of the Earth surface, yet the open ocean marine atmosphere is one of the most poorly probed atmospheric environments of our planet. In the tropics, deep convective clouds form and provide a mechanism to inject boundary-layer air into the uppermost free troposphere (15 km). The vertical distribution and potential climate relevance of gases such as glyoxal (CHOCHO) or iodine oxide remains poorly characterized, partly because of the lack of measurement techniques capable of measuring these gases from aircraft. Glyoxal is a short-lived gas that forms climate-cooling secondary organic aerosol (SOA). Iodine oxide forms by destroying tropospheric ozone, and can nucleate new particles.
My research group has designed and assembled a prototype Airborne Multi-Axis Differential Absorption Spectroscopy instrument (CU AMAX-DOAS) that measures glyoxal, iodine oxide, bromine oxide, nitrogen dioxide, formaldehyde, and other gases sensitively and selectively with a single, portable instrument directly in the open atmosphere, by aircraft. Five telescopes mounted in a pylon below the wing observe scattered solar photons in the zenith, nadir, slant forward and backward, and forward viewing directions (Figure 1), and are coupled via optical fiber to a set of two spectrometer/charged couple devices detector systems located inside the aircraft fuselage. The instrument was first deployed in January 2010 aboard the NSF High-performance Instrumented Airborne Platform for Environmental Research aircraft (Gulfstream V). During a first science flight from Hawaii to the tropical Pacific Ocean south of Hawaii (Figure 2), the CU AMAX-DOAS measured, for the first time, elevated concentrations of glyoxal (Figure 2 inset), formaldehyde, and iodine oxide inside the boundary layer. The vertical distribution was measured into the free troposphere. The presence of these gases more than 5,000 km from any land is surprising because of their very short atmospheric lifetimes (on the order of seconds to hours), and indicates previously unrecognized open ocean sources for hydrocarbons and reactive halogen species. Ours are the first observations of glyoxal in the remote free troposphere.
Honors and Awards
- NSF CAREER Award recipient, 2009
- Feodor-Lynen Fellow (2005-2007)
- Henry & Camille Dreyfus Fellow (2002-2004)
- Marie Curie Fellow (1998-2000)
- Erasmus Fellow (1992-1993)