Validation of nitric acid retrieved by the IMK-IAA processor from MIPAS/ENVISAT measurements

[摘要] The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboardthe ENVISAT satellite provides profiles of temperature and varioustrace-gases from limb-viewing mid-infrared emission measurements. Thestratospheric nitric acid (HNO₃) from September 2002 to March 2004was retrieved from the MIPAS observations using the science-oriented dataprocessor developed at the Institut für Meteorologie und Klimaforschung(IMK), which is complemented by the component of non-local thermodynamicequilibrium (non-LTE) treatment from the Instituto de Astrofísica deAndalucía (IAA). The IMK-IAA research product, different from the ESAoperational product, is validated in this paper by comparison with a numberof reference data sets. Individual HNO₃ profiles of the IMK-IAA MIPASshow good agreement with those of the balloon-borne version of MIPAS(MIPAS-B) and the infrared spectrometer MkIV, with small differences of lessthan 0.5 ppbv throughout the entire altitude range up to about 38 km, and below 0.2 ppbv above 30 km. However, the degreeof consistency is largely affected by their temporal and spatial coincidence,and differences of 1 to 2 ppbv may be observed between 22 and 26 km at high latitudes near the vortex boundary, due to large horizontalinhomogeneity of HNO₃. Statistical comparisons of MIPAS IMK-IAAHNO₃ VMRs with respect to those of satellite measurements ofOdin/SMR, ILAS-II, ACE-FTS, as well as the MIPAS ESA product show goodconsistency. The mean differences are generally ±0.5 ppbv andstandard deviations of the differences are of 0.5 to 1.5 ppbv. Themaximum differences are 2.0 ppbv around 20 to 25 km. This givesconfidence in the general reliability of MIPAS HNO₃ VMR data and theother three satellite data sets.

[学科分类] 大气科学