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  • International Foundation HFSJG Activity Report 2010

    28

    Name of research institute or organization:

    Federal Office of Meteorology and Climatology MeteoSwiss, Payerne Title of project: Global Atmosphere Watch Radiation Measurements Project leader and team: Dr. Laurent Vuilleumier, project leader Dr. Martine Collaud Coen, Mr. Olaf Maier Project description: In 2010, radiation measurements at the Jungfraujoch were carried out satisfactorily. Some minor problems still affected direct irradiance measurements. But a complete technical and software update of the control system of the cupola protecting direct irradiance instruments was achieved end of 2009, and perfected during 2010. This update allowed greatly improving the performance of the cupola. In average, the data availability for radiation parameters reached 93% at the Jungfraujoch in 2010 (01.11.200931.10.2010). MeteoSwiss also enhanced its collaboration with other institutions performing monitoring or research within the 2010 CLACE campaign.

    The CLACE campaigns focus on the interactions between aerosols and clouds especially in situations where ice crystals and supersaturated droplets coexist. These situations are observed in situ at the Jungfraujoch during such campaigns. While specific aerosol and cloud parameters are measured by various Swiss and foreign institutions including the PSI, MeteoSwiss performs operational measurements of radiation and makes them available for analyses per-formed within the CLACE collaboration. In 2010, MeteoSwiss devoted specific efforts to guarantee that aerosol optical depth obser-vations (AOD) can be resumed and made available. MeteoSwiss also provided supplementary measure-ments characterizing the behavior of air masses before they arrive at Jungfraujoch. For example, the average vertical wind speed component in the cloud is expected to in-fluence the cloud peak supersaturation. This study aims at predicting the super-saturation from the meteoro-logical parameters using a thermodynamic cloud model.

    Jungfraujoch

    Temperature profiler

    Windprofiler

    Figure 1: view of the Kleine Scheidegg (2060 masl) showing a micro-wave temperature profiler radiometer and a 1,3 GHz wind profiler radar operated by MeteoSwiss during CLACE 2010 campaign.

  • International Foundation HFSJG Activity Report 2010

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    To obtain such information on regional cloud dynamics, additional instruments were installed at the Kleine Scheidegg (see Fig. 1). The behavior of the planetary boundary layer height will also be studied by instruments at the Kleine Scheidegg and compared to the aerosol measurements at the Jungfraujoch, which exhibit large differences between situations with free tropospheric and PBL influenced air masses. The 2010 CLACE campaign included data from:

    a 1,29 GHz wind profiler radar (MeteoSwiss, see Fig. 2 and 3), and a [50-58] GHz temperature profiler radiometer (MeteoSwiss, see Fig 4).

    The temperature profiler recorded the brightness temperatures of the atmosphere in the [50-58] GHz band at several elevation angles, from which a profile of air temperature in function of height is retrieved. The wind profiler recorded horizontal wind speed and wind direction above Kleine Scheidegg from 2350 m to 4000 m asl. In addition it measured the vertical air velocity and direction (upward, downward).

    Figure 2: Evolution of wind vertical profiles (direction and speed [m/s]) above Kleine Scheidegg for August 2-4: winds from southwest on August 2nd and 4th, west on August 3rd

    Figure 3: Evolution of vertical air motion [m/s] (+ down, - up) above Kleine Scheidegg for August 2-4: episodes of descending air masses are in light orange and yellow.

  • International Foundation HFSJG Activity Report 2010

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    MeteoSwiss AOD measurements are made with precision filter radiometers (PFRs, Wehrli, 2000) at four sites of the Swiss Alpine Climate Radiation Monitoring network (SACRaM) including Jungfraujoch since the mid-1990s (see Fig. 5 as well as Schmid et al., 1997; Ingold et al., 2001). PFRs are designed for long-term monitoring, and 4-wavelength models have been installed at most GAW (Global Atmosphere Watch) baseline stations. Such sun photometers have a number of features to reduce long-term instrumental drift, for example: temperature stabili-zation to within 0.1C, and a shutter to reduce filter and sensor degradation. Meteo-Swiss operates four 4-wave-length PFR units at each of the four SACRaM sites, which allows the deter-mination of AOD at 9 wave-lengths and integrated water vapor column at 3 wave-lengths. Such data have been analyzed in different studies (e.g., see Ruckstuhl et al., 2008 and Nyeki et al., 2005); but measurements were interrupted in 2007, and because of technical diffi-culties they were resumed only in 2009.

    Figure 4: Evolution of vertical temperature profiles at Kleine Scheidegg (preliminary) for August 2 to 4: air warming seems correlated with vertical downward air motion.

    Figure 5: Picture of the PFR sun-photometers in the Jungfraujoch SACRaM cupola.

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    PFR measurements after resuming normal operations were used for deriving AOD using a preliminary set of Langley calibration performed in situ and made available to the CLACE collaboration. Comparison with measurements taken before 2007 showed that 2010 data did not differ significantly with previous data (see Fig. 6)

    References: Ingold, T., C. Mtzler, A. Heimo and N. Kmpfer (2001) Aerosol optical depth measurements by means of a Sun photometer network in Switzerland. J. Geophys. Res., 106, 27537-27554.

    Nyeki, S., L. Vuilleumier, J. Morland, A. Bokoye, P. Viatte, C. Mtzler, and N. Kmpfer (2005), A 10-year integrated atmospheric water vapor record using precision filter radiometers at two high-alpine sites. Geophys. Res. Lett., 32, L23803, http://dx.doi.org/10.1029/2005GL024079

    Ruckstuhl, C., R. Philipona, K. Behrens, M. Collaud Coen, B. Drr, A. Heimo, C Mtzler, S. Nyeki, A. Ohmura, L. Vuilleumier, M. Weller, C. Wehrli and A. Zelenka, (2008) Aerosol and cloud effects on solar brightening and the recent rapid warming. Geophys. Res. Lett., 35, L12708, http://dx.doi.org/10.1029/2008GL034228.

    Schmid, B., C. Mtzler, A. Heimo and N. Kmpfer (1997) Retrieval of optical depth and particle size distribution of tropospheric and stratospheric aerosols by means of sun photometry. IEEE Transactions on Geosciences and Remote Sensing, 35, 172-182.

    Wehrli, C. (2000), Calibrations of filter radiometers for determination of atmospheric optical depths, Metrologia, 37, 419-422

    Figure 6: Jungfraujoch AOD at 500nm (blue: multi-year half-day averages compiling all data prior to 2007, red: 2010 hourly averages, magenta: 2010 half-day averages).

  • International Foundation HFSJG Activity Report 2010

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    Key words: Solar irradiance, ultraviolet, visible, infrared, spectral irradiance, precision filter radiometer (PFR), pyranometer, pyrheliometer, UV biometer, total aerosol optical depth (AOD), integrated water vapor (IWV). Internet data bases: http://wrdc-mgo.nrel.gov/ (World Radiation Data Centre WRDC) http://www.iapmw.unibe.ch/research/projects/STARTWAVE/database/ (IWV STARWAVE data) Collaborating partners/networks:

    Radiation data submitted to the World Radiation Data Centre (WRDC, St. Petersburg, Russian Federation) within the framework of the Global Atmosphere Watch.

    Participation to CLACE 2010 campaign Study of solar photometry (aerosol optical depth) and longwave infrared

    radiative forcing in collaboration with the Physikalisch-Meteorologisches Observatorium Davos (PMOD) World Radiation Center (WRC).

    Scientific publications and public outreach 2010: Conference papers Vuilleumier, L. and D. Walker, Estimation of cloud effect on UV erythemal irradiance using SW irradiance data, Eleventh BSRN Scientific Review and Workshop, Queenstown, New Zealand, 13-16 April 2010, Summary Report from the Eleventh BSRN Scientific Review and Workshop, 14 (2010) http://www.gewex.org/BSRN/BSRN-11_Report-final.pdf

    Vuilleumier, L. and D. Walker, Evolution of surface reflectivity in Switzerland between 1980 and 2008, Eleventh BSRN Scientific Review and Workshop, Queenstown, New Zealand, 13-16 April 2010, Summary Report from the Eleventh BSRN Scientific Review and Workshop, 16-17 (2010) http://www.gewex.org/BSRN/BSRN-11_Report-final.pdf

    Data books and reports Ozone, rayonnement et arosols (GAW) in Annalen 2009 MeteoSchweiz, Zrich SZ ISSN 0080-7338 pp. 115131. Address: Office fdral de mtorologie et de climatologie MtoSuisse Station Arologique ch. de lArologie CH-1530 Payerne Contacts: Laurent Vuilleumier Tel.: +41 26 662 6306 Fax: +41 26 662 6212 e-mail: laurent.vuilleumier@meteoswiss.ch URL: http://www.meteoswiss.ch/web/en/climate/climate_international/gaw-ch/radiation.html

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