Climatologies of Stratospheric Short-Lived Species from Odin/SMR
Khosravi, Maryam; Murtagh, Donal; Urban, Jo
Chalmers University of Technology, SWEDEN
The Sub-Millimetre Radiometer (SMR) on board the Odin satellite has been measuring stratospheric species including short-lived ones since Odin's launch in 2001. The long-term Odin dataset is therefore available for climatology studies. Odin as a sun-synchronous satellite measures at certain local times with its a.m. /p.m. observations around sunrise and sunset. Due to the drift of Odin's orbit in local solar time at the equator and measurements at different local times, a correction is required before trends can be evaluated. Since Odin measures around sunrise and sunset, even a small change in solar zenith angle could lead to a large affect on the concentration of short-lived species which are strongly dependent on photo-chemistry.
A 1D model is used for diurnal scaling of the Odin data. In this comparison, a scaling factor is calculated to scale the observations to a specific local time (or solar zenith angle). The model has been verified using observations by limb-viewing satellite instruments of short-lived species in the tropics and in the altitude range from the middle stratosphere to the lower mesosphere. In the next step, the model will be verified with other models.
For this paper, chlorine monoxide (ClO) and Nitrogen oxide (NO) have been chosen as examples. Scaling factors are used to obtain solar zenith angle corrected climatologies for Odin short-lived species. The uncertainties and limitations will be estimated by checking the internal consistency of the results, as scaled a.m. values versus p.m. values should give the same trend. In a further step, these climatologies will be evaluated against other satellite data sets. The paper will focus on a detailed presentation of the climatologies and the limitations.