The Impact of Cirrus Clouds on Retrieval of Ozone in the Upper Troposphere / Lower Stratosphere from SMILES Data

Within the last decade, a number of satellite sub-mm limb sounding missions has been developed with Odin/SMR[10] and EOSMLS[17]among them now operating successfully for several years. While focused on measuring atmospheric trace gase profiles, frequent observations of upper tropospheric ice clouds by these instruments are expected according to previous studies[3] [5]and have recently been demonstrated in the measurements[6] [18]. This sensitivity to ice clouds, that is supported by the very long path lenghts through atmospheric layers characteristic for limb measurements, facilitates the detection of cirrus and the retrieval of cloud properties. On the other hand, the “contamination” of molecular emission and absorption spectra by clouds complicates trace gas retrievals. Although a number of radiative transfer forward models are capable of considering ice clouds, especially of their scattering features, atmospheric profiles are usually retrieved assuming clearsky conditions (first attempts of retrievals from cloudy measurements have just recently been presented by Ekström et al. [4]). That means, not taken into account in the inversion procedure, cloud effects on measured signal introduce uncertainties and errors in the estimation of the atmospheric profiles. In comparison to the aforementioned operating missions, the SMILES instrument, planned to be operated on the Japanese Experimental Module (JEM) of the International Space Station (ISS) from the year 2009, fea-