Final conference, Rome October 11, 2016 Surface radiation budget and role of clouds during the 2016 Study of the water VApour in the polar AtmosPhere (SVAAP) campaign at Thule, Greenland Daniela Meloni1, Tatiana Di Iorio1, Alcide di Sarra1, Antonio Iaccarino1, Giandomenico Pace1, Gabriele Mevi2, Giovanni Muscari2, Marco Cacciani3, Julian Gröbner4 1Laboratory for Observations and Analyses of Earth and Climate, ENEA, Italy, e-mail: daniela.meloni@enea.it; 2Istituto Nazionale di Geofisica e Vulcanologia, Italy; 3Physics Department, University of Rome “La Sapienza”, Italy; 4PMOD/WRC, Switzerland. Abstract The radiative balance of the Earth-atmosphere system is the driving motor of climate change, and polar regions are the most sensitive, at global level, to such changes [Serreze and Francis, 2006]. Among different factors, water vapour and clouds have the most important influence on surface radiative budget (SRB) in the polar regions, acting with complex feedback mechanisms [Curry et al., 1995; 1996]. For such reason there is an urgent need to investigate the cloud impact on the atmospheric radiative budget. The determination of cloud properties from satellite is problematic [Kato et al., 2006], thus requiring either long term measurements or intensive field campaigns. The climate observatory at Thule (76.5° N, 68.8° W), Greenland, is devoted to climate change studies since 90’s, with an international effort of different institutions: DMI, NCAR, ENEA, INGV, University of Rome (http://www.thuleatmos-it.it). The Study of the water Vapour in the polar AtmosPhere (SVAAP) project, funded by the Italian Programme for Antarctic Research, is aimed at investigating the surface radiation budget, the variability of atmospheric water vapour, and the long-term variations in stratospheric composition and structure at Thule, in the framework of the international Network for Detection of Atmospheric Composition Change (NDACC). The SRB investigation is a common focus of both SVAAP and ARCA projects, the radiation balance being a key quantity in air-surface interaction. In addition to continuing the long term measurements of stratospheric parameters, the project includes the realization of an intensive field campaign, which offered the possibility to study the cloud physical and optical properties and their impact on the surface radiative budget. The field campaign was held from 5 to 28 July 2016. The instruments already operating at Thule observatory were: a lidar system for the stratospheric temperature profile (during nighttime) and of the tropospheric backscattering profile [di Sarra et al., 1998; di Sarra et al., 2002; Di Biagio et al., 2010], an Eppley PSP pyranometer and a Kipp&Zonen CGR4 pyrgeometer for the downward shortwave (SW) and longwave (LW) irradiance [Di Biagio et al., 2012], respectively, and the millimeter-wave spectrometer GBMS [Muscari et al., 2007; 2012] capable of measuring the stratospheric and mesospheric chemical composition. New instruments for the SRB and for the characterization of the atmospheric state were installed for the campaign: an Eppley PSP pyranometer and a PIR pyrgeometer for the upward SW and LW irradiance, respectively; two Licor 190R sensors for the upwelling and downwelling photosynthetically active radiation (PAR); a Metcon actinometer for the downward actinc flux in the 280-700 nm spectral range; a modified CG3 pyrgeometer measuring downward irradiance in the 8-14 µm infrared window; a Hatpro microwave radiometer for the temperature and relative humidity tropospheric profiles, the integrated water vapour (IWV), and the liquid water path (LWP); VESPA-22 microwave spectrometer [Bertagnolio et al., 2012] for stratospheric water vapour profiles and IWV; a Heitronics infrared (9.6-11.5 µm) pyrometer for the sky brightness temperature (BT); a visible and an infrared sky cameras for the cloud cover; a meteorological