Evidence of scattering of tropospheric radiation by PSCs in mid‐IR limb emission spectra: MIPAS‐B observations and KOPRA simulations

Höpfner, Michael; Oelhaf, H.; Wetzel, G.; Friedl-Vallon, Felix; Kleinert, Anne; Lengel, A.; Maucher, G.; Nordmeyer, H.; Glatthor, N.; Stiller, G. P.; Clarmann, T. von; Fischer, H.; Kröger, C.; Deshler, Terry

doi:10.1029/2001gl014443

Cited by 75 publications

(97 citation statements)

References 23 publications

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“…The forward modeling accounted for Mie scattering through a calculation of extinction coefficient for the PSC particles but did not explicitly include terrestrial or solar scattering into the line of sight of the instrument. However at 820 cm À1 , these effects, as reported by Höpfner et al [2002], do not show any ability to produce distinct infra-red bands such as the one observed in this study.…”

Section: à3mentioning

confidence: 43%

“…In particular, observations of Arctic PSCs obtained with a balloon-borne instrument (MIPAS-B2) coupled with simulations of the observed spectra have shown that large PSC particles (>1 mm mean radius) could scatter significant fractions of upwelling tropospheric radiation into limb views [Höpfner et al, 2002]. Höpfner et al also reported a sharp step observed between 815 and 825 cm À1 and attributed the change in gradient to the n 2 band of the NO 3 À ion in nitric acid containing PSC particles.…”

Section: Introductionmentioning

confidence: 99%

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Observations of a distinctive infra‐red spectral feature in the atmospheric spectra of polar stratospheric clouds measured by the CRISTA instrument

Spang

Remedios

2003

Geophysical Research Letters

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Polar stratospheric cloud particles (PSCs) are known to strongly influence the infra‐red emission spectrum of the lower stratosphere in cold polar winters. The characteristics of these infra‐red features have been examined using limb sounding spectra recorded by the CRISTA experiment in August 1997 when many Antarctic PSCs were observed. A distinctive spectral feature centered at 820 cm−1 has been identified in many of these spectra, the first time that a particular band has been observed in the spectra of PSCs in the atmosphere. The feature can be attributed to the ν2 band of the NO3− ion and strongly suggests a condensed nitric acid component to the particles in the form of solid nitric acid trihydrate (NAT) or liquid ternary solution (STS). The spectral signatures belong to a definite sub‐set of the PSC observations recorded by CRISTA. The particles are observed at temperatures well above 192 K, allowing for temperature errors, and it is suggested that NAT particles are the most likely source of the spectral signature. In addition, it is shown that PSC events in which no spectral signature is present are only observed below 192 K and display a very similar HNO3‐temperature relationship to STS particles.

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Section: à3mentioning

confidence: 43%

Section: Introductionmentioning

confidence: 99%

Observations of a distinctive infra‐red spectral feature in the atmospheric spectra of polar stratospheric clouds measured by the CRISTA instrument

Spang

Remedios

2003

Geophysical Research Letters

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“…There is also a small but strong feature at this wave number range (Fig. 2), caused by the ν 2 band emissions of NO − 3 (Höpfner et al, 2002). In previous laboratory measurements of NAT refractive indices, the feature was not pronounced enough to reproduce the atmospheric infrared limb observations of the signature; but in a reanalysis of the Biermann et al (2000) NAT film measurements in conjunction with radiative transfer model calculation, Höpfner et al (2006a) showed the unambiguous assignment that NAT particles with r < 3 µm produce the spectral signature in the measured spectra.…”

Section: Two-colour Ratio Methodsmentioning

confidence: 90%

A multi-wavelength classification method for polar stratospheric cloud types using infrared limb spectra

et al. 2016

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Abstract. The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument on board the ESA Envisat satellite operated from July 2002 until April 2012. The infrared limb emission measurements represent a unique dataset of daytime and night-time observations of polar stratospheric clouds (PSCs) up to both poles. Cloud detection sensitivity is comparable to space-borne lidars, and it is possible to classify different cloud types from the spectral measurements in different atmospheric windows regions.Here we present a new infrared PSC classification scheme based on the combination of a well-established two-colour ratio method and multiple 2-D brightness temperature difference probability density functions. The method is a simple probabilistic classifier based on Bayes' theorem with a strong independence assumption. The method has been tested in conjunction with a database of radiative transfer model calculations of realistic PSC particle size distributions, geometries, and composition. The Bayesian classifier distinguishes between solid particles of ice and nitric acid trihydrate (NAT), as well as liquid droplets of super-cooled ternary solution (STS).The classification results are compared to coincident measurements from the space-borne lidar Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument over the temporal overlap of both satellite missions (June 2006-March 2012. Both datasets show a good agreement for the specific PSC classes, although the viewing geometries and the vertical and horizontal resolution are quite different. Discrepancies are observed between the CALIOP and the MI-PAS ice class. The Bayesian classifier for MIPAS identifies substantially more ice clouds in the Southern Hemisphere polar vortex than CALIOP. This disagreement is attributed in part to the difference in the sensitivity on mixed-type clouds. Ice seems to dominate the spectral behaviour in the limb infrared spectra and may cause an overestimation in ice occurrence compared to the real fraction of ice within the PSC area in the polar vortex.The entire MIPAS measurement period was processed with the new classification approach. Examples like the detection of the Antarctic NAT belt during early winter, and its possible link to mountain wave events over the Antarctic Peninsula, which are observed by the Atmospheric Infrared Sounder (AIRS) instrument, highlight the importance of a climatology of 9 Southern Hemisphere and 10 Northern Hemisphere winters in total. The new dataset is valuable both for detailed process studies, and for comparisons with and improvements of the PSC parameterizations used in chemistry transport and climate models.

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“…The retrieval model used is the KOPRA-KOPRAFIT (Karlsruhe Optimized and Precise Radiative transfer Algorithm) suite, allowing us to directly retrieve aerosol parameters from observed radiances by coupling a Mie model with the line-by-line radiative transfer scheme Höpfner et al, 2002Höpfner et al, , 2006. For aerosol composition we assume a 75 % by weight (75 wt %) H 2 SO 4 -H 2 O solution, as the stratospheric sulfuric aerosol composition typically varies between around 70 and 80 %, as obtained by equilibrium calculations (Carslaw et al, 1995) and observations (e.g.…”

Section: Chemical Transport Modelmentioning

confidence: 99%

MIPAS observations of volcanic sulfate aerosol and sulfur dioxide in the stratosphere

et al. 2018

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Abstract. Volcanic eruptions can increase the stratospheric sulfur loading by orders of magnitude above the background level and are the most important source of variability in stratospheric sulfur. We present a set of vertical profiles of sulfate aerosol volume densities and derived liquidphase H 2 SO 4 (sulfuric acid) mole fractions for 2005-2012, retrieved from infrared limb emission measurements performed with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board of the Environmental Satellite (Envisat). Relative to balloon-borne in situ measurements of aerosol at Laramie, Wyoming, the MIPAS aerosol data have a positive bias that has been corrected, based on the observed differences to the in situ data. We investigate the production of stratospheric sulfate aerosol from volcanically emitted SO 2 for two case studies: the eruptions of Kasatochi in 2008 and Sarychev in 2009, which both occurred in the Northern Hemisphere midlatitudes during boreal summer. With the help of chemical transport model (CTM) simulations for the two volcanic eruptions we show that the MIPAS sulfate aerosol and SO 2 data are qualitatively and quantitatively consistent with each other. Further, we demonstrate that the lifetime of SO 2 is explained well by its oxidation by hydroxyl radicals (OH). While the sedimentation of sulfate aerosol plays a role, we find that the long-term decay of stratospheric sulfur after these volcanic eruptions in midlatitudes is mainly controlled by transport via the BrewerDobson circulation. Sulfur emitted by the two midlatitude volcanoes resides mostly north of 30 • N at altitudes of ∼ 10-16 km, while at higher altitudes (∼ 18-22 km) part of the volcanic sulfur is transported towards the Equator where it is lifted into the stratospheric "overworld" and can further be transported into both hemispheres.

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Evidence of scattering of tropospheric radiation by PSCs in mid‐IR limb emission spectra: MIPAS‐B observations and KOPRA simulations

Cited by 75 publications

References 23 publications

Observations of a distinctive infra‐red spectral feature in the atmospheric spectra of polar stratospheric clouds measured by the CRISTA instrument

Observations of a distinctive infra‐red spectral feature in the atmospheric spectra of polar stratospheric clouds measured by the CRISTA instrument

A multi-wavelength classification method for polar stratospheric cloud types using infrared limb spectra

MIPAS observations of volcanic sulfate aerosol and sulfur dioxide in the stratosphere

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