MIPAS methane succesfully validated

Bias estimation of MIPAS methane retrievals with respect to satellite reference instruments. The quantity shown is the mean estimate over all latitudes of (MIPAS-REFERENCE)/REFERENCE x 100 %. This validation study includes bias determination, assessment of stability, precision validation, analysis of histograms and comparison of climatologies. The reference instruments include the satellite instruments ACE-FTS, HALOE, SOFIE and SCIAMACHY; as well as MkIV balloon-borne solar occultation measurements and cryogenic whole-air sampling measurements.

Above 50 km altitude, MIPAS methane mixing ratios agree within 3% with ACE-FTS and SOFIE. Between 30 and 40 km an agreement within 3% with SCIAMACHY has been found. In the middle stratosphere, there is no clear indication of a MIPAS bias since comparisons with various instruments contradict each other. In the lower stratosphere (below 25 km) MIPAS CH₄ is biased high with respect to satellite instruments, and the most likely estimate of this bias is 14 %. However, in the comparison with CH₄ data obtained from cryogenic whole-air sampler (cryosampler) measurements, there is no evidence of a high bias in MIPAS between 20 and 25 km altitude. Precision validation is performed on collocated MIPAS–MIPAS pairs and suggests a slight underestimation of its uncertainties by a factor of 1.2. No significant evidence of an instrumental drift has been found.

For more details see: http://www.atmos-meas-tech.net/8/5251/2015/amt-8-5251-2015.pdf