MIPAS reference atmospheres and comparisons to V4.61/V4.62 MIPAS level 2 geophysical data sets

Abstract. Small volcanic ash particles have long residence times in the troposphere and the stratosphere so that they have significant impact on the Earth's radiative budget and consequently affect climate. For global long-term observations of volcanic aerosol, infrared limb measurements provide excellent coverage, sensitivity to thin aerosol layers, and altitude information. The optical properties of volcanic ash and ice particles, derived from micro-physical properties, have opposing spectral gradients between 700 and 960 cm −1 for small particle sizes. Radiative transfer simulations that account for single scattering showed that the opposing spectral gradients directly transfer to infrared limb spectra. Indeed, we found the characteristic spectral signature, expected for volcanic ash, in measurements of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) after the eruption of the Chilean volcano Puyehue-Cordón Caulle in June 2011. From these measurements we derived an ash detection threshold function. The empirical ash detection threshold was confirmed in an extensive simulations study covering a wide range of atmospheric conditions, particle sizes and particle concentrations for ice, volcanic ash and sulfate aerosol. From the simulations we derived the upper detectable effective radius of 3.5 µm and the detectable extinction coefficient range of 5 × 10 −3 to 1 × 10 −1 km −1 . We also showed that this method is only sensitive to volcanic ash particles, but not to volcanic sulfate aerosol. This volcanic ash detection method for infrared limb measurements is a fast and reliable method and provides complementary information to existing satellite aerosol products.

Section: Simulation Setupmentioning

confidence: 99%

“…The spectra were simulated for a tangent altitude of 10 km, neglecting the MIPAS field of view. These pencil beam simulations were made for the full-resolution mode of MIPAS assuming the mid-latitude atmosphere from Remedios et al (2007). The homogeneous cloud layer was placed at 10 to 10.5 km altitude.…”

Section: Figure 2 (A)mentioning

confidence: 99%

Volcanic ash detection with infrared limb sounding: MIPAS observations and radiative transfer simulations

Grießbach¹,

Hoffmann²,

Spang³

et al. 2014

“…This study uses atmospheric profiles from a climatology (Remedios et al, 2007) in the mid-latitudes to simulate infrared spectra as they would be measured by GLORIA at 15 km flight altitude. The GLORIA Measurement Simulator uses vertical profiles of relevant trace species and of pressure and temperature from the climatology and combines them in a forward model with the GLORIA measurement geometry.…”

Section: Study Conceptmentioning

confidence: 99%

Characterization of blackbody inhomogeneity and its effect on the retrieval results of the GLORIA instrument

Kleinert

Krisch²,

Ungermann³

et al. 2018

Abstract. Limb sounding instruments play an important role in the monitoring of climate trends, as they provide a good vertical resolution. Traceability to the International System of Units (SI) via onboard reference or transfer standards is needed to compare trend estimates from multiple instruments. This study investigates the required uncertainty of these radiation standards to properly resolve decadal trends of climate-relevant trace species like ozone, water vapor, and temperature distribution for the Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA). Temperature nonuniformities of the onboard reference blackbodies, used for radiometric calibration, have an impact on the calibration uncertainty. The propagation of these nonuniformities through the retrieval is analyzed. A threshold for the maximum tolerable uncertainty of the blackbody temperature is derived, so that climate trends can be significantly identified with GLORIA.

“…The IG2 climatological database is a collection of atmospheric profiles used as initial guess (IG) or assumed profiles in MIPAS routine level 2 retrievals (Remedios et al, 2007). The IG2 database includes vertical profiles of pressure, temperature and volume mixing ratio (VMR) of constituents relevant for MIPAS data processing.…”

Section: Atmospheric Modelsmentioning

confidence: 99%

“…-the US Standard Atmosphere, 1976 (US Gov., 1976), -the IG2 atmosphere (Remedios et al, 2007), -the atmosphere retrieved in a previous processing version of MIPAS data (Raspollini et al, 2013),…”

Section: Atmospheric Modelsmentioning

confidence: 99%

Characterization of model errors in the calculation of tangent heights for atmospheric infrared limb measurements

Ridolfi

Sgheri

2014

Abstract. We review the main factors driving the calculation of the tangent height of spaceborne limb measurements: the ray-tracing method, the refractive index model and the assumed atmosphere. We find that commonly used ray tracing and refraction models are very accurate, at least in the midinfrared. The factor with largest effect in the tangent height calculation is the assumed atmosphere. Using a climatological model in place of the real atmosphere may cause tangent height errors up to ± 200 m. Depending on the adopted retrieval scheme, these errors may have a significant impact on the derived profiles.