Radiative impact of water vapour in the Upper Troposphere and Lower Stratosphere (UTLS) from a new merged satellite data

Water vapour in the upper troposphere and lower stratosphere (UTLS) has a significant impact both on the radiative and chemical properties of the atmosphere. As there are strong vertical gradients in water vapour around the tropopause, reliable water vapour observations are essential to assess the radiative impact from this transition layer. Within the ESA Water Vapour Climate Change Initiative, a new vertically resolved water vapour dataset up to the lower stratosphere is merged from a set of limb and nadir satellite observations from 2010 to 2014. The new dataset shows large improvement on the water vapour in the UTLS region. With this new data, an off-line radiative transfer model is used to estimate the radiative forcing from water vapour in the UTLS assuming different reanalyses as reference states.