Ten years of MIPAS measurements with ESA Level 2 processor V6

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is a limb-viewing infrared Fourier transform spectrometer that has been measuring, since July 2002, the three dimension distribution of atmospheric composition on board the ESA ENVISAT satellite. MIPAS acquired atmospheric spectra sampled at 0.025 cm-1 from July 2002 to March 2004 (full resolution measurements), and since January 2005 has been operating at 0.0625 cm-1 sampling (optimized resolution measurements). For the operations with reduced maximum path difference, a new scenario was adopted that exploits the reduction in measurement time of each interferometer sweep and uses a finer vertical sampling. We analyze the performance of the MIPAS operational products (target species) in term of random and systematic errors, vertical and horizontal resolution, as well as the consistency of the products in the two phases of MIPAS mission (full resolution and optimized resolution measurements). The performed analysis proves that for the target species the profiles from optimized resolution measurements are characterized by an improved horizontal resolution (about 510 km for full resolution measurements, about 410 km for optimized resolution measurements) and improved vertical resolution (varying, in the altitude range 10-40 km, between 3 and 5 km for full resolution measurements and between 1.5 and 4 km for optimized resolution measurements). The random and systematic error performances, thanks to the redundant information on the target species present in MIPAS spectra and the consequent use of dedicated microwindows in the two phases (larger spectral intervals being used for optimized resolution measurements), are generally comparable in the two phases. The study on the consistency of the products in the two phases of the mission (made comparing profiles retrieved from the same measurements, but using the spectral intervals that have been selected for the analysis respectively of full resolution and optimized resolution measurements) indicates that, apart from a few exceptions, generally occurring at the borders of the retrieval range, average differences between optimized resolution and full resolution measurements are within the estimated systematic errors of the profiles relative to each phase of the measurements, confirming that the estimation of systematic errors is appropriate. The long term time series of the target species covering the mission lifetime will also be addressed, discussing some annual and inter-annual variability of the retrieved profiles and the correlations between the profiles of different species.