Critical parameters for the retrieval of mesospheric water vapour and temperature from Odin/SMR limb measurements at 557Â GHz

Limb measurements at 557 GHz by the Sub-millimetre and Millimetre Radiometer (SMR) onboard the Odin satellite provide water vapour and temperature information throughout the mesosphere. A sensitivity study for these retrievals has been performed, in order to identify the most critical parameters affecting the retrievals, with focus on the polar summer mesosphere conditions. Uncertainties in the instrument characterisation and the a priori value chosen for the pointing offset were found to have significant effects on the retrieved profiles. It is also shown that spectroscopic parameters play a role. An obvious improvement of the water and temperature retrieval can be obtained when we account for some of these critical parameters. However, some further improvement of the instrument behaviour characterisation is still needed.