Comparison of the H2O, HDO and δD stratospheric climatologies between the MIPAS-ESA v8, MIPAS-IMK v5 and ACE-FTS v4.1/4.2 satellite data sets.

Variations in the isotopological composition of water vapour are fundamental for understanding the relative importance of different mechanisms of water vapor transport from the tropical upper troposphere to the lower stratosphere. Previous comparisons obtained from observations of H₂O and HDO by satellite instruments showed discrepancies. In this work, newer versions of H₂O and HDO retrievals from Envisat/MIPAS are compared with data derived from SCISAT/ACE-FTS. Specifically, MIPAS-IMK V5, MIPAS-ESA V8, and ACE-FTS V4.1/4.2 for the common period from February 2004 to April 2012 are compared for the first time through a profile-to-profile approach and comparison based on climatological structures. Stratospheric H₂O and HDO global average coincident profiles reveal good agreement. The smallest biases are found between 20 and 30 km, and the largest biases are exhibited around 40 km both in absolute and relative terms. For HDO, biases between -8.6–10.6 % are observed among the three databases in the altitudes of 16 to 30 km. However, around 40 km, ACE-FTS agrees better to MIPAS-IMK than MIPAS-ESA, with biases of -4.8 % and -37.5 %, respectively. The HDO bias between MIPAS-IMK and MIPAS ESA is 28.1 % at this altitude. The meridional cross-sections of H₂O and HDO exhibit the expected distribution that has been established in previous studies. The tape recorder signal is present in H₂O and HDO for the three databases with slight quantitative differences. The meridional cross-sections of δD are in good agreement with the previous version of MIPAS-IMK and ACE-FTS data. In the temporal δD variations, the results suggest that in the current data versions, the calculated isotopic composition (δD) from MIPAS-IMK aligns more closely with expected stratospheric behavior for the entire stratosphere. Nevertheless, there are differences in the climatological δD composites between databases that could lead to different interpretations regarding the water vapor transport processes toward the stratosphere, so it is important to intercompare these δD observations. [ABSTRACT FROM AUTHOR]