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Introduction:

 DOAS observations from aircraft have been performed for many years. Airborne observations offer a number of advantages

• access to remote areas

• ability to probe large latitudinal / longitudinal transsects in a short time

• measurements without cloud interference.

For stratospheric measurements, mainly zenith-sky observations are of interest. Using limb (horizon) observations, very long light paths at flight altitude can be obtained, providing excellent detection limits which is particularly important in the tropopause region. In addition, vertical profiles can be obtained by either changing flight altitude or by using observations under different elevation angles and applying appropriate inversion algorithms.

For tropospheric measurements, nadir observations are suited best and by selecting the flight pattern appropriately, emission plumes can be probed at different distances from a source providing information on emission strength and atmospheric lifetime of a substance. By using measurements at different wavelengths, some vertical resolution can be obtained even if the flight altitude is not varied.

If an imaging spectrometer is used in nadir view, several measurements across track can be taken in parallel, and as the aircraft moves forward, a stripe of spatially resolved trace gas observations is created. This observation mode is similar to that from a satellite, only that the lower flight altitude and slower forward movement allows for much better spatial resolution.

In addition to emission monitoring and determination of spatial patterns of trace gas distributions, airborne DOAS observations are also well suited for validation of satellite observations.

The IUP Bremen has developed and operated two types of airborne DOAS instruments for which more information is available:

• Airborne Multi Axis DOAS (AMAX-DOAS)

• Imaging DOAS (iDOAS)

References:

• Schönhardt, A., Altube, P., Richter, A., Krautwurst, S., Gerilowski, K., Burrows, J.P., Aircraft measurements of anthropogenic NO2 with an imaging DOAS instrument, DPG Spring meeting, Berlin, Germany, March 2012
• Schönhardt, A., Richter, A., Krautwurst, S., Gerilowski, K., Wittrock, F., Burrows, J. P., A new airborne imaging DOAS instrument - development and first measurements, 5th International DOAS Workshop, Mainz, Germany, July 2011
• P. Altube Vázquez, Aircraft measurements of tropospheric NO2 with an imaging DOAS instrument, Master Thesis, University of Bremen, August 2012
• Bruns, M., Buehler, S. A., Burrows, J. P., Richter, A., Rozanov, A., Wang, P., Heue, K.-P., Platt, U., Pundt, I., Wagner, T., NO2 Profile Retrieval using airborne multi axis UV-visible skylight absorption measurements over central Europe, Atmos. Chem. Phys., 6, 3049-3058, 2006
• P. Wang, A. Richter, M. Bruns, J. P. Burrows, W. Junkermann, K.-P. Heue, T. Wagner, U. Platt, I. Pundt, Airborne multi-axis DOAS measurements of tropospheric SO₂ plumes in the Po-valley, Italy, Atmos. Chem. Phys., 6, 329-338, 2006
• Project "SCIAMACHY validation with airborne DOAS observations" final report (in German)
• Fix, A., Ehret, G., Flentje, H., Poberaj, G., Gottwald, M., Finkenzeller, H., Bremer, H., Bruns, M., Burrows, J. P., Kleinböhl, A., Küllmann, H., Kuttippurath, J., Richter, A., Wang, P., Heue, K.-P., Platt, U.,  Pundt, I.,  Wagner, T., SCIAMACHY validation by aircraft remote sensing: design, execution, and first measurement results of the SCIA-VALUE mission, Atmos. Chem. Phys., 5, 1273-1289, 2005
• K.-P. Heue, A. Richter, T. Wagner, M. Bruns, J. P. Burrows, C. v. Friedeburg, W. D. Lee, U. Platt, I. Pundt, P. Wang,
Validation of SCIAMACHY tropospheric NO₂-columns with AMAXDOAS measurements, Atmos. Chem. Phys., 5, 1039-1051, 2005
• Wang, P., A. Richter, M. Bruns, V. V. Rozanov, J. P. Burrows, K.-P. Heue, T. Wagner, I. Pundt, U. Platt, Measurements of tropospheric NO₂ with an airborne multi-axis DOAS instrument, Atmos. Chem. Phys., 5, 337-343, 2005
• M. Bruns: NO2 Profile Retrieval using Airborne Multiaxis Differential Optical Absorption Spectrometer (AMAXDOAS) data, PhD Thesis, University of Bremen, 2004
• Bruns, M., S. Bühler, J. P. Burrows, K.-P. Heue, U. Platt, I. Pundt, A. Richter, A. Rozanov, T. Wagner, P. Wang, Retrieval of Profile Information from Airborne Multi Axis UV/visible Skylight Absorption Measurements, Applied Optics, 43 (22), 4415-4426, 2004

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