Senior scientist, Physikalisch-Meteorologisches Observatorium Davos, World Radiation Center, Davos Dorf, Switzerland.
Claus Fröhlich and his team at PMOD/WRC have been pioneers in research of solar radiation, its variations and impact upon the atmosphere and climate.
PMOD/WRC provides the world standard for global radiation, against which regional centers calibrate their instruments. As World Radiation Center PMOD is obliged to maintain and continuously improve absolute radiometers. Instruments developed at PMOD/WRC are among the most precise and stable ones. Besides developing and maintaining highly precise absolute radiometers, PMOD/WRC is, since 1996,the World Optical Depth Research and Calibration Center, too. For this purpose a 4-channel filter radiometer was developed, which serves for monitoring atmospheric turbidity, in a network of presently 12 stations.
In addition, Claus Fröhlich and his team have been pioneers in UV radiation research and monitoring, as well as research on infrared radiation. PMOD/WRC presently operates a network of 11 highly precise infrared radiometers working over a high profile between 370 m and 3580 m altitude, enabling to quantify the height dependance of the radiation budget, with the goal of quantitatively proving the variation of the Earth’s greenhouse effect.
Claus Fröhlich’s by far most important achievements are related to his space experiments. In 1988 already, he could prove for the first time, from his IPHIR experiment aboard PHOBOS, solar oscillations.
His experiment SOVA is, from the Swiss point of view, something special, as it operated aboard the satellite EURECA, which was released from the Space Shuttle Atlantis in 1992,by a Swiss astronaut, and safely returned one year later to the Kennedy Space Flight Center.
Claus Fröhlich’s most successful space experiment is VIRGO aboard SOHO, which has been measured, with very high precision, the Sun’s radiation since 1996.The instruments comprising VIRGO investigate the varying radiation flux towards Earth as well as solar oscillations enabling Helio-Seismology for understanding the Sun’s interior.
Atmospheric Physics : Interaction of solar radiation with the atmosphere; diagnostic of the atmosphere with radiation measurements; Earth=s radiation budget and solar influence on climate.
Solar Physics : Solar "constant" and its variability; influence of solar activity on spectral and total irradiance; helioseismology by irradiance measurements; relation between characteristics of solar oscillations and irradiance.
His space radiation experiments have enabled him to determine the solar radiation flux outside the Earth’s atmosphere, over more than 2 solar cycles, with very high accuracy. This pioneering work (see for instance C. Froehlich and J. Lean: The Sun’s total irradiance: Cycles, trends and related climate change uncertainties since 1976,Geophys.Res.Lett.25,4377,1998) is the basis for calibrating solar-terrestrial relations over these 2 solar cycles, which has enabled reconstruction of the solar radiation flux over the past 1000 years from proxy data. This is one of the most important and exciting links for understanding global climate fluctuations over the last millennium, and certainly an outstanding achievement in solar-terrestrial research.
EGU Julius Bartels Medallist 2005 "for his outstanding work on solar radiation and its influence on the terrestrial atmosphere and climate"
Member of Academia Europaea; International Academy of Astronautics; International Astronomical Union, European Astronomical Society (founding member), European Geophysical Society, American Geophysical Union, European and Swiss Physical Society.
D. Schmucki, S. Voigt, R. Philipona, C. Fröhlich, J. Lenoble, A. Ohmura and Ch. Wehrli: Effective Albedo derived from UV Measurements in the Swiss Alps, Journal of Geophysical Research, Vol. 106, No. D6, p. 5369 – 5383, 2001
C. Fröhlich and M. Anklin: Uncertainty of Total Solar Irradiance: An Assessment of the Last 20 Years of Space Radiometry, Metrologia, 37, 387-391, 2000
C. Fröhlich: Total solar irradiance variations since 1978, Adv. Space Res., Vol. 29, No. 10, pp. 1409 – 1416, 2002
W. Finsterle and C. Fröhlich: Low-Order p Modes from VIRGO Irradiance Data, Solar Physics 200: p. 393-406, 2001
C. Fröhlich, T. Appourchaux and D. Gough: Dependence on Azimuthal Order of the Amplitudes of Low-Degree p Modes, in A. Willson (ed.), Helio and Asteroseismology at the Dawn of the Millenium, ESA SP-464, ESA Publications Division, Noordwijk, The Netherlands, 2001
C. Fröhlich and W. Finsterle: Total Solar Irradiance from VIRGO on SoHO, in A.Willson (ed.), The Solar Cycle and Terrestrial Climate, Santa Cruz de Tenerife, Spain, 25.-29 September 2000, ESA SP-463, ESA Publications Division, Noordwijk, The Netherlands, 2000
C. Fröhlich and W. Finsterle: VIRGO Radiometry and Total Solar Irradiance 1996-2000 Revised, in P.Brekke, B.Fleck and J.B. Gurman (eds.), Recent Insights into the Physica of the Sun and Heliosphere – Highlights from SoHO and other Space Missions ASP Conference Series, Vol. 200, 2001
J. R. Kuhn, L. Floyd, C. Fröhlich, J. M. Pap: Using Precise Solar Limb Shape: Measurements to study the Solar Cycle, in Space Science Reviews 94, 169-176, 2000
E. Vocks, R. Busch, C. Fröhlich, S. Borelli, H. Mayer and J. Ring: Influence of weather and climate on subjective symptom intensity in atopic eczema, in International Journal of Biometeorology, 45, 27 – 30, 2001
T. Appourchaux, B. Andersen, G. Berthomieu, W. Chaplin, Y. Elsworth, W. Finsterle, C. Fröhlich, D. Gough, J.T. Hoeksema, G. Isaak, A. Kosovichev, J. Provost, P. Scherrer, T. Sekii, T. Toutain: G-mode detection: Where do we stand? In: P. Pall´e and A. Wilson (eds), Helio- and Asteroseimology at the dawn of the Millenium, ESA SP-464, ESA Publications Division, Noordwijk, The Netherlands, p. 467, 2001
C. Fröhlich, W. Finsterle: VIRGO Radiometry and Total Solar Irradiance 1996-2000 Revised. In: P. Brekke, B. Fleck, and J.B. Gurman (eds.), Recent Insights into the Physics of the Sun and Heliosphere: Highlights from SOHO and other Space Missions, ASP Conf. Ser., IAU Symp. 203, p. 105–108, 2001
M. Fligge, S. K. Solanki, J. M. Pap, C. Fröhlich, Ch. Wehrli: Variations of solar spectral irradiance from near UV to the infrared - measurements and results, Journal of Atmospheric and Solar-Terrestrial Physics 63, 1479-1487, 2001
Ch. Marty, R. Philipona, C. Fröhlich, A. Ohmura: Altitude dependence of surface radiation fluxes and cloud forcing in the Alps: Results from the Alpine Surface Radiation Budget Network, Theoretical and Applied Climatology, Vol. 72, 137 – 155, 2002
J. Pap, C. Fröhlich, J. Kuhn, S. Sofia, R. Ulrich: A discussion of recent evidence for solar irradiance variability and climate, Adv. Space Research, Vol. 29, No. 10, pp. 1417 – 1426, 2002
J. Pap, M. Turmon, L. Floyd, C. Fröhlich, and Ch. Wehrli: Total solar and spectral irradiance variations from Solar Cycles 21 to s23, Adv. Space Research, Vol. 29, No. 12, pp. 1923 - 1932, 2002
J. Pap and C. Fröhlich: International Solar Cycle Studies (ISCS), “Solar Energy Flux Study: From the Interior to the Outer Layer” – Working Group 1 Report, in Adv. Space Research, Vol. 29, No. 10, pp. 1571 – 1582, 2002
C. Fröhlich and C. Wehrli: Variability of Spectral Solar Irradiance from VIRGO/SPM Observations, PMOD/WRC internal report, 2002
C. Fröhlich and J. Lean: Solar Irradiance Variability and Climate, in Astron. Nachrichten, Vol. 23, No. 3 / 4, pp. 203 – 212, 2002
C. Fröhlich: Long-Term Behaviour of Space Radiometers, in Metrologia, Vol. 40, p. 60 – 65, 2003
C. Fröhlich: Solar Irradiance Variability, Solar Energy Flux Variations, in AGU, Geophysical Monograph Series, Vol. 141, p. 97 – 110, 2004
C. Fröhlich: Solar Irradiance Variations, in: A. Wilson (eds.) Proceedings of the ISCS Symposium Solar Variability as an Input to the Earth’s Environment, ESA SP-535, ESA Publications Division, Noordwijk, The Netherlands, p. 183 – 194, 2003
N. Fox, J. Aiken, J.J. Barnett, X. Briottet, R. Carvell, C. Fröhlich, S.B. Groom, O. Hagolle, J.D. Haigh, H.H. Kieffer, J. Lean, D.B. Pollock, T. Quinn, M.C.W. Sandford, M. Schaepman, K.P. Shine, W. Schmutz, P.M. Teillet, K.J. Thome, M.M. Verstraete, E. Zalewski: Traceable radiometry underpinning terrestrial- and helio-studies (TRUTHS), Advances an Space Research, 32, 2253-2261, 2003