Influence of clouds on the spectral actinic flux density in the lower troposphere (INSPECTRO): overview of the field campaigns S. Thiel1, L. Ammannato2, A. Bais3, B. Bandy4, M. Blumthaler5, B. Bohn6, O. Engelsen7, G. P. Gobbi2, J. Gröbner8,*, E. Jäkel9,******, W. Junkermann1, S. Kazadzis3, R. Kift10, B. Kjeldstad11, N. Kouremeti3, A. Kylling12,**, B. Mayer13, P. S. Monks14, C. E. Reeves4, B. Schallhart5, R. Scheirer13,***, S. Schmidt9,****, R. Schmitt15, J. Schreder16, R. Silbernagl5,*****, C. Topaloglou3, T. M. Thorseth11,*******, A. R. Webb10, M. Wendisch9,******, and P. Werle1 1Institut für Meteorologie und Klimaforschung (IMK-IFU), Forschungszentrum Karlsruhe, Garmisch-Partenkirchen, Germany 2Istituto di Scienze dell'Atmosfera e del Clima (ISAC-CNR), Consiglio Nazionale delle Ricerche, Rome, Italy 3Aristotle University of Thessaloniki, Laboratory of Atmospheric Physics, Thessaloniki, Greece 4School of Environmental Sciences, University of East Anglia, Norwich, UK 5Division of Biomedical Physics, Innsbruck Medical University, Innsbruck, Austria 6Forschungszentrum Jülich, ICG Institut 2: Troposphäre, Jülich, Germany 7Norwegian Institute for Air Research (NILU), Polar Environmental Centre, Tromso, Norway 8Institute for Health and Consumer Protection (IHCP), Physical and Chemical Exposure Unit, European Comission – Joint Research Center (JRC), Ispra, Italy 9Institute for Tropospheric Research (IFT), Leipzig, Germany 10University of Manchester, School of Earth, Atmospheric and Environmental Science, Manchester, UK 11Dept. of Physics, Norwegian University of Science and Technology, Trondheim, Norway 12Norwegian Institute for Air Research (NILU), Oslo, Norway 13Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Oberpfaffenhofen, Germany 14Department of Chemistry, University of Leicester, Leicester, UK 15Meteoconsult GmbH, Glashütten, Germany 16CMS Ing. Dr. Schreder GmbH, Kirchbichl, Austria *now at: Physikalisch-Meteorologisches Observatorium Davos, World Radiation Center (PMOD/WRC), Dorfstrasse 33, 7260 Davos Dorf, Switzerland **now at: St. Olavs Hospital, Trondheim Univ. Hospital, and Alesund Hospital, Alesund, Norway ***now at: Swedish Meteorological and Hydrological Institute (SMHI), Folkborgsvägen 1, 60176 Norrköping, Sverige ****now at: University of Colorado, Laboratory for Atmospheric and Space Physics, Duane Physics Building, Room D-337, University of Colorado, Boulder, CO 80309-0311, USA *****now at: Institut f. Medizinischen Strahlenschutz und Dosimetrie, Landeskrankenhaus Innsbruck, Innrain 66, 6020 Innsbruck ******now at: Institute for Atmospheric Physics, Johannes Gutenberg-University Mainz, Becherweg 21, 55099 Mainz, Germany *******now at: Sor Trondelag University College, Faculty of Technology, 7004 Trondheim, Norway
Abstract. Ultraviolet radiation is the key factor driving tropospheric photochemistry.
It is strongly modulated by clouds and aerosols. A quantitative
understanding of the radiation field and its effect on photochemistry is
thus only possible with a detailed knowledge of the interaction between
clouds and radiation. The overall objective of the project INSPECTRO was the
characterization of the three-dimensional actinic radiation field under
cloudy conditions. This was achieved during two measurement campaigns in
Norfolk (East Anglia, UK) and Lower Bavaria (Germany) combining space-based,
aircraft and ground-based measurements as well as simulations with the
one-dimensional radiation transfer model UVSPEC and the three-dimensional
radiation transfer model MYSTIC.
During both campaigns the spectral actinic flux density was measured at
several locations at ground level and in the air by up to four different
aircraft. This allows the comparison of measured and simulated actinic
radiation profiles. In addition satellite data were used to complete the
information of the three dimensional input data set for the simulation. A
three-dimensional simulation of actinic flux density data under cloudy sky
conditions requires a realistic simulation of the cloud field to be used as
an input for the 3-D radiation transfer model calculations. Two different
approaches were applied, to derive high- and low-resolution data sets, with
a grid resolution of about 100 m and 1 km, respectively.
The results of the measured and simulated radiation profiles as well as the
results of the ground based measurements are presented in terms of
photolysis rate profiles for ozone and nitrogen dioxide. During both
campaigns all spectroradiometer systems agreed within ±10% if
mandatory corrections e.g. stray light correction were applied. Stability
changes of the systems were below 5% over the 4 week campaign periods
and negligible over a few days. The J(O1D) data of the single
monochromator systems can be evaluated for zenith angles less than 70°,
which was satisfied by nearly all airborne measurements during both
campaigns. The comparison of the airborne measurements with corresponding
simulations is presented for the total, downward and upward flux during
selected clear sky periods of both campaigns. The compliance between the
measured (from three aircraft) and simulated downward and total flux
profiles lies in the range of ±15%.
Citation: Thiel, S., Ammannato, L., Bais, A., Bandy, B., Blumthaler, M., Bohn, B., Engelsen, O., Gobbi, G. P., Gröbner, J., Jäkel, E., Junkermann, W., Kazadzis, S., Kift, R., Kjeldstad, B., Kouremeti, N., Kylling, A., Mayer, B., Monks, P. S., Reeves, C. E., Schallhart, B., Scheirer, R., Schmidt, S., Schmitt, R., Schreder, J., Silbernagl, R., Topaloglou, C., Thorseth, T. M., Webb, A. R., Wendisch, M., and Werle, P.: Influence of clouds on the spectral actinic flux density in the lower troposphere (INSPECTRO): overview of the field campaigns, Atmos. Chem. Phys., 8, 1789-1812, doi:10.5194/acp-8-1789-2008, 2008.