Version 8 IMK-IAA MIPAS temperatures from 12-15 µm spectra: Middle and Upper Atmosphere modes

Motivated by an improved European Space Agency (ESA) version of calibrated Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) spectra (version 8.03), we have released version 8 of MIPAS temperatures and pointing information retrieved from 2005-2012 MIPAS measurements at 12-15 µm in the Middle Atmosphere (MA), Upper Atmosphere (UA) and Noctilucent Cloud (NLC) measurement modes. The Institute of Meteorology and Climate Research-Instituto de Astrofisica de Andalucia (IMK-IAA) retrieval processor in use considers non-local thermodynamic equilibrium (non-LTE) emission explicitly for each limb scan. This non-LTE treatment is essential to obtain accurate temperatures above the mid-mesosphere because at the altitudes covered, up to 115 km, the simplified climatology-based non-LTE treatment employed for the Nominal (NOM) measurements is insufficient. Other updates in MA/UA/NLC version 8 non-LTE temperature retrievals from previous data releases include more realistic atomic oxygen and carbon dioxide abundances, an updated set of spectroscopic data, an improved spectral shift retrieval, a continuum retrieval extended to altitudes up to 58 km, consideration of an altitude-dependent radiance offset retrieval, the use of wider microwindows above 85 km to capture the offset, an improved accuracy in forward model calculations, new a priori temperature information, improved temperature horizontal gradient retrievals and the use of MIPAS version 5 interfering species where available. The resulting MIPAS MA/UA/NLC IMK-IAA temperature dataset is reliable for scientific analysis in the full measurement vertical range for the MA (18-102 km) and the NLC (39-102 km) observations and from 42 to 115 km for the UA observations. The random temperature errors, dominated by the instrumental noise, are typically less than 1 K below 60 km, 1-3 K at 60-70 km, 3-5 K at 70-90 km, 6-8 K at 90-100 km, 8-12 K at 100-105 km and 12-20 K at 105-115 km. Random pointing correction errors, also mainly arising from instrumental noise, are on average 50 m for tangent altitudes up to 60 km and decrease linearly to values smaller than 20 m for altitudes above 95 km. The vertical resolution is 3 km at altitudes below 50 km, 3-5 km at 50-70 km, 4-6 km at 70-90 km, 6-10 km at 90-100 km and 8-11 km at 100-115 km. The systematic errors in retrieved temperatures below 75 km are driven by uncertainties in the CO<SUB>2</SUB> spectroscopic data and, above 80 km, by uncertainties in the non-LTE model parameters (including collisional rates and atomic oxygen abundance) and the CO<SUB>2</SUB> abundance. These lead to systematic temperature errors of less than 0.7 K below 55 km, 1 K at 60-80 km, 1-2 K at 80-90 km, 3 K at 95 km, 6-8 K at 100 km, 10-20 K at 105 km and 20-30 K at 115 km. Systematic errors in the tangent altitude correction, mainly arising from CO<SUB>2</SUB> spectroscopic uncertainties, are 250 m at 20 km, 200 m at 40-60 km, 100 m at 80 km and smaller than 50 m above 90 km. The consistency between the MA/UA/NLC and the NOM IMK-IAA datasets is excellent below 70 km (typical 0.5-1 K differences). The comparison of this temperature dataset with co-located Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperature measurements shows excellent agreement, with differences typically within 1.5 K below 90 km, 1-3 K at 90-95 km, 1-5 K at 95-100 km, 1-8 K at 100-105 km and 1-10 K above. The agreement with SABER improves with respect to previous MIPAS IMK-IAA data versions.