Climatologies of stratospheric short-lived species from Odin/SMR: Methodology for ClO

Other conference contribution, 2013

The Sub-Millimetre Radiometer (SMR) on board the Odin satellite has been measuring short-lived strato- spheric species such as chlorine monoxide (ClO) since Odin’s launch in 2001. Odin/SMR at its sun-synchronous orbit measures at certain local times observations around sunrise and sunset at the equator. Due to the drift of Odin’s orbit in local solar time and the fact that mea- surements are done at different local times, a correction is required before a monthly zonal mean climatology can be calculated and trends of ClO can be evaluated. To deal with this, scaling factors are calculated using a photo-chemical box model for correction of the mixing ratios respective to a reference time. The uncertainties and limitations of this method are estimated by checking the internal consistency of the results, so that comparing the scaled a.m. ClO time-series to p.m. scaled time- series should give the same results. We found out that scaling SMR ClO to the ascending time of Microwave Limb Sounder (MLS) as reference at about 1.30 a.m. at the equator gives better result compared to the scaling ClO to MLS descending node at about 1.30. p.m. The time series calculated for the morning SMR ClO scaled (to 1.30 a.m.) agrees with the evening ClO scaled.