Comparison of surface shortwave and longwave fluxes at the Thule High Arctic Atmospheric Observatory, Greenland, with CERES products.

Determination of shortwave (SW) and longwave (LW) radiation from space is fundamental in regions where few surface observations are available. This is particularly important in the Arctic due to the complex feedback mechanisms affecting climate in this region. Few sites located in the Arctic region provide surface radiation flux (SRF) measurements long enough to conduct systematic comparisons with satellite products. Long-term measurements of downward and upward SW (DSI and USI) and LW irradiances (DLI and ULI) are carried out at the Thule High Arctic Atmospheric Observatory (THAAO, $76.5^{\circ}$ N, $68.8^{\circ}$ W), in North-Western Greenland. DSI and DLI measurements were started in 2009, and USI and ULI in 2016. In this analysis the four SRF components have been compared with Level 3 Clouds and the Earth's Radiant Energy System (CERES) surface products, to assess the agreement between ground-based and satellite-derived radiation data. On a monthly basis the comparison shows good agreement, with mean negative bias of -4.4 Wm{}^{-2}$ for DSI (CERES data underestimates in situ ones), and a mean positive bias of 2.3 Wm${}^{-2}$ for DLI, possibly associated to cloud effects.