Validation of MIPAS-ENVISAT Version 4.61 Operation Data with Balloon and Aircraft Measurement:H2O

Embedded in the ENVISAT validation programme of the chemistry instruments GOMOS, MIPAS, and SCIAMACHY, a number of remote sensing and in situ techniques from balloon and aircraft platforms were employed since the launch of Envisat on March 1, 2002. In this paper we will be focusing on the validation of MIPAS-Envisat (MIPAS-E) off-line products, by presenting the results of the intercomparison between MIPAS-E H2O vertical profiles as well as aircraft and balloon correlative measurements as obtained within the ESABC programme (1). First priority is given to the validation of processor v4.61 data. However, to get a more complete picture, individual results of 2002 and 2003 balloon observations are also compared with earlier versions of the MIPAS-E operational processor or with data processed with scientific processors run at expert support laboratories. Some general remarks are finally expressed, along with specific recommendations to fully exploit the available ESABC validation dataset. Unfortunately, by the date of the ACVE-2 conference, re-analyzed operational MIPAS-E data was almost only available for the year 2002 limiting the number of validation cases with the new operational version 4.61 (v4.61). Based on these few cases, the MIPAS-E H2O profiles as processed with v4.61 are in good agreement with airborne observations between about 15 and 30 km altitude in all cases with a good coincidence in time and space between the MIPAS-E observations and the correlative measurements. However, due to the very limited number of good validation cases available so far, this statement cannot yet been regarded as conclusive and representative. Low biases in MIPAS- E H2O compared to the correlative measurements appear frequently in the lowermost stratosphere pointing at a retrieval problem in this crucial altitude region. Retrievals of MIPAS-E H2O profiles as obtained by different processors appear to be generally rather robust as proven by a statistics of inter- comparisons of H2O profiles between the operational v4.61 data and data processed with the IMK scientific processor, provided that a considerable number of spurious and unphysical data has been removed from the v4.61 data prior to the statistical assessment. This points at the need for an automatic quality control of the operationally retrieved H2O data. Further validation coincidences in different geophysical situations will have to be considered using v4.61 data before a final quantitative assessment on the quality of the MIPAS-E operational H2O data can be given.