Name: Christoph Hoffmann
PhD-project title: Investigation of the subsidence of air masses in the mesosphere in the north polar region using CO as a tracer
The global atmospheric circulation leads to a subsidence of air masses in the mesosphere at the winter pole. Since the mesosphere is influenced by high-energy radiation and particles from space, mesospheric air contains radicals like NOX which are able to enter the stratosphere at the winter pole due to this subsidence. There they affect the polar stratospheric chemistry, especially the ozone-chemistry. Thus, the subsidence of mesospheric air causes a coupling of the stratosphere to space-influences.
To quantify and model the resulting effects, it is necessary to determine exact subsidence rates. This can be done by measuring the abundances of species which are not affected by chemical processes in the respective timescales and thus show only dynamic influences. CO can act as such a tracer.
In the past, there have been measurements of mesospheric CO using groundbased and spaceborne techniques and subsidence rates have been derived in a few cases. But these measurements are limited to short time-periods or do not cover the winter pole.
In this project, a new microwave radiometer for the measurement of CO up to 80 km altitude will be constructed and installed at the AWIPEV Research Base in Ny Ålesund, Spitsbergen to perform continuous measurements of mesospheric CO in the north polar region. These measurements will be used to derive continuous subsidence rates, which will be compared to a model (see project of Nadine Wieters). A further aim is the enhancement of the model according to the results.
As mesospheric CO abundances are expected to show further features, such as seasonal variations and responses to wave-activity, the measured and modelled data will also be analysed with respect to these processes.
Start of doctoral thesis: 16.07.2008 | Defence: 20.04.012
Supervisor: Prof. Dr. Justus Notholt (Uni-HB/IUP)
Co-supervisor: Dr. Mathias Palm (Uni-HB/IUP)
Further members: Dr. Markus Rex (AWI/Potsdam)
Dr. C. von Savigny (Uni-HB/IUP)
Christoph G. Hoffmann, D. E. Kinnison, R. R. Garcia, M. Palm, J. Notholt, U. Raffalski, and G. Hochschild. CO at 40-80 km above Kiruna observed by the ground-based microwave radiometer KIMRA and simulated by the Whole Atmosphere Community Climate Model. Atmos. Chem. Phys., 12:3261-3271, 2012. doi:10.5194/acp-12-3261-2012
Christoph G. Hoffmann, U. Raffalski, M. Palm, B. Funke, S. H. W. Golchert, G. Hochschild, and J. Notholt. Observation of strato-mesospheric CO above Kiruna with ground-based microwave radiometry — retrieval and satellite comparison. Atmos. Meas. Tech., 4:2389-2408, 2011. doi:10.5194/amt-4-2389-2011
Mathias Palm, Christoph G. Hoffmann, Sven H.W. Golchert und Justus Notholt: The ground-based MW radiometer OZORAM on Spitsbergen - description and validation of stratospheric and mesospheric O3-measurements, Atmos. Meas. Tech., 3, 1533-1545, doi:10.5194/amt-3-1533-2010, 2010.
Christoph G. Hoffmann, Mathias Palm, Bernd Funke, Douglas Kinnison, Rolando R. Garcia, Uwe Raffalski, Sven H. W. Golchert, Gerd Hochschild, Justus Notholt: Comparison of Middle Atmosphere CO datasets above Kiruna (68°N), VIIth MIPAS IMK/IAA Data User Meeting, Granada, Spain, 11.-12. May 2011 (oral)
Christoph G. Hoffmann, Uwe Raffalski, Mathias Palm, Douglas E. Kinnison, Rolando R. Garcia, Sven H. W. Golchert, Gerd Hochschild, Justus Notholt: Ground-based Observations of the Tracer CO above the Arctic and the Comparison to SD-WACCM model data, 3rd HEPPA Workshop, Granada, Spain, 9.-11. May 2011 (Poster)
Christoph G. Hoffmann, U. Raffalski, M. Palm, S. H. W. Golchert, G. Hochschild, J. Notholt: Observation of the Descent of Mesospheric Air above the Arctic during the Northern Winter 2009/2010 using the Tracer CO, AGU Fall Meeting, San Francisco, 13.-17. Dezember 2010 (Poster)
Christoph G. Hoffmann, U. Raffalski, M. Palm, S. H. W. Golchert, G. Hochschild, J. Notholt: Observation of the Descent of Mesospheric Air above the Arctic, COSPAR 38th scientific assembly, Berlin, 18. - 25. July 2010 (oral)
Christoph G. Hoffmann, U. Raffalski, M. Palm, S. H. W. Golchert, G. Hochschild, J. Notholt: Observation of Descending Mesospheric Air above the Arctic during the Winters of 2007 to 2010 by Ground-based Microwave Radiometry, SCOSTEP's Symposium STP 12, Berlin, 12.-16. July 2010 (oral)
Christoph G. Hoffmann, U. Raffalski, M. Palm, S. H. W. Golchert, G. Hochschild, J. Notholt: Bestimmung von Absinkraten mesosphärischer Luft über der Arktis durch Messung des Tracers CO, DPG-Frühjahrstagung 2010, Hannover, 8.-12. März 2010.
Christoph G. Hoffmann, M. Palm, G. Kopp, U. Raffalski, S. H. W. Golchert, G. Hochschild, J. Notholt, "Measurement of Subsidence Rates in the Middle Atmosphere during the Winter Season over Northern Polar Regions, EGU General Assembly, 19 - 24 April 2009. (Pdf)
Christoph G. Hoffmann, M. Palm, G. Kopp, U. Raalski, S. H. W. Golchert, G. Hochschild, J. Notholt: Investigation of the Subsidence of Mesospheric Air over the Arctic and its Impact on the Ozone Layer, ESSReS Retreat 1, Bremerhaven, 21. August 2009.
M. Palm, Christoph G. Hoffmann, S. H. W. Golchert, J. Notholt und G. Hochschild: Measurements of mesospheric O3 and H2O using ground-based millimeterwave radiometry in the high Arctic, EGU General Assembly, Wien, 2009.
Mathias Palm, Nadine Wieters, Christoph G. Hoffmann, Miriam Sinnhuber, Sven Golchert, Justus Notholt:
Variation of the Mesospheric Ozone above the Arctic caused by solar in influence observed by ground-based millimeterwave radiometry, SCOSTEP's Symposium STP12, Berlin, 12.-16. Juli 2010.
Laura Holt, Cora Randall, Lynn Harvey, Christoph Hoffmann: An evaluation of tracer-derived descent rates using model and observational results, 3rd HEPPA Workshop, Granada, Spain, 9.-11. May 2011 (Poster)
Svalbard, Ny Alesund, 21 September - 8 October 2008: Preparations for the installation of a CO microwave radiometer
DAAD stipend from 17 September until 18 December 2010 for a research stay at the National Center for Atmospheric Research (NCAR), Boulder, Colorado, USA
Christoph G. Hoffmann, Observation of Descending Mesospheric Air above the Arctic, ESSReS-Retreat 18 June 2010, “Talk award”