Assessment of Quality of MIPAS ESA V8 Products

Abstract

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is a limb-viewing infrared Fourier transform spectrometer that operated from 2002 to 2012 onboard the ENVISAT satellite. The analysis of MIPAS measurements allows to study the temporal evolution of numerous species of interest for the study of the ozone in the stratosphere, pollutants and many green-house gases. The objective of the MIPAS Quality Working Group is to improve the quality of the MIPAS products through a fruitful collaboration among spectroscopists, Level 1, Level 2, and validation teams. A large effort has recently led to implement significant improvements in both ESA Level 1 and Level 2 processors, as well as in spectroscopic database and in some absorption cross-sections in order to improve the quality of the products. In addition to the products already present in the V7 dataset (temperature and the VMR of H2O, O3, HNO3, CH4, N2O, NO2, CFC-11, CFC-12, N2O5, ClONO2, HCFC-22, COF2, CF4, HCN and CCl4), the VMR of six additional species (OCS, CH3Cl, HDO, C2H2, C2H6, COCl2) will be provided in V8 dataset. In order to evaluate the impact of the changes in the products before full mission reprocessing, the analysis of the performances of the products of the modified L1 and L2 processors, as well as the auxiliary data, has been performed on a Diagnostic DataSet (DDS). The orbits of the DDS have been chosen in coincidence with correlative measurements for performing also a preliminary assessment of the accuracy of the products and to evaluate possible changes in the drift. With respect to V7 products, main improvements consist in a reduction of the temperature bias in the first part of the mission, a reduction of the discontinuities in CH4 and N2O time series due to daily gain upgrade, a better filtering of clouds and a better handling of horizontal inhomogeneities. The results of the assessment of the quality of MIPAS measurements will be shown, as well as the study of the temporal evolution and variability of all species. We will also investigate the spatial, seasonal, and interannual variations in the distribution of these species.