Comparison of high-latitude line-of-sight ozone column density with derived ozone fields and the effects of horizontal inhomogeneity

Swartz, W. H.; Yee, Jeng‐Hwa; Randall, C. E.; Shetter, R. E.; Browell, Edward V.; Burris, J.; McGee, Thomas J.; Avery, M. A.

doi:10.5194/acp-6-1843-2006

Cited by 5 publications

(2 citation statements)

References 23 publications

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“…This does not imply that the temperature field inhomogeneities are the only cause for deviations of 1-D retrieved vmr profiles from true atmospheric state, as it is known that inhomogeneities in the species vmr fields might well cause significant deviations too (Swartz et al, 2006). However, for mid IR limb sounding the temperature profile is a key quantity with strong influence on all species retrievals, which makes it so important to know this quantity as accurate as possible.…”

Section: Modified 1-d Retrievalsmentioning

confidence: 99%

Impact of temperature field inhomogeneities on the retrieval of atmospheric species from MIPAS IR limb emission spectra

et al. 2010

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We examine volume mixing ratios (vmr) retrieved from limb emission spectra recorded with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board Envisat. In level 2 (L2) data products of three different retrieval processors, which perform one dimensional (1-D) retrievals, we find significant differences between species' profiles from ascending and descending orbit parts. The relative differences vary systematically with time of the year, latitude, and altitude. In the lower stratosphere their monthly means can reach maxima of 20% for CFC-11, CFC-12, HNO3, H2O, 10% for CH4 and N2O. Relative differences between monthly means of 1-D retrieval results and of the true atmospheric state can be expected to reach half of these percentage values, while relative differences in single vmr profiles might well exceed those numbers. Often there are no physical or chemical reasons for these differences, so they are an indicator for a problem in the data processing. The differences are generally largest at locations where the meridional temperature gradient of the atmosphere is strong. On the contrary, when performing the retrieval with a tomographic two dimensional (2-D) retrieval, L2 products generally do not show these differences. This suggests that inhomogeneities in the temperature field, and possibly in the species' fields, which are accounted for in the 2-D algorithm and not in standard 1-D processors, may cause significant deviations in the results. Inclusion of an externally given adequate temperature gradient in the forward model of a 1-D processor helps to reduce the observed differences. However, only the full tomographic 2-D approach is suitable to resolve the horizontal inhomogeneities. Implications for the use of the 1-D data, e.g. for validation, are discussed. The dependence of the ascending/descending differences on the observation strategy suggests that this problem may affect 1-D retrievals of infrared limb sounders, if the line of sight of the instrument has a significant component in the direction of the horizontal temperature variation

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Section: Modified 1-d Retrievalsmentioning

confidence: 99%

Impact of temperature field inhomogeneities on the retrieval of atmospheric species from MIPAS IR limb emission spectra

et al. 2010

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“…Recently, Swartz et al [2006] have pointed out that spatial inhomogeneities in the line‐of‐sight measurements from aircraft are likely to affect the retrieval of vertical profiles of species like ozone. Therefore a doubt remains regarding the NO 2 quantities measured in the polar vortex, especially in the lower stratosphere where significant amounts of NO 2 have been recurrently observed by remote‐sensing balloon‐borne instruments [ Sen et al , 1998; Payan et al , 1999; Wetzel et al , 2002; Rivière et al , 2002; Berthet et al , 2003].…”

Section: Introductionmentioning

confidence: 99%

Remote‐sensing measurements in the polar vortex: Comparison to in situ observations and implications for the simultaneous retrievals and analysis of the NO₂ and OClO species

Berthet¹,

Renard²,

Catoire³

et al. 2007

J. Geophys. Res.

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[1] Nighttime remote-sensing balloon observations conducted by the SALOMON instrument in the arctic polar vortex in January 2006 reveal high amounts of stratospheric NO 2 in the lower stratosphere similarly to previously published profiles. NO 2 concentration enhancements are also present in the vertical profiles observed by the GOMOS instrument on board the Envisat satellite and obtained coincidently to the balloon measurements. Such quantities are not present in in situ observations obtained by the SPIRALE instrument in similar geophysical conditions. While OClO amounts are acceptably reproduced by Chemistry Transport Model (CTM) calculations, NO 2 simulated values are well below the observed quantities. The examination of the slant column densities of NO 2 obtained at float altitude highlights unexpected strong enhancements with respect to the elevation angle and displacement of the balloon. It is shown that these fluctuations result from NO 2 spatial inhomogeneities located above the balloon float altitude. Potential vorticity maps reveal the presence of midlatitude NO 2 -rich air in the upper stratosphere or lower mesosphere as a result of the perturbed dynamical situation of the vortex. The presence of spatial inhomogeneities crossed by the lines of sight leads to artificial high concentration values of NO 2 in the vertical profile retrieved from the slant column densities assuming spatial homogeneity. A direct implication is that the differences previously observed between measurements of NO 2 and OClO and model results are probably mostly due to the improper inversion of NO 2 in the presence of perturbed dynamical conditions or when mesospheric NO x production events occur. The dynamical situation will have to be systematically analyzed in future studies involving remote-sensing observations.Citation: Berthet, G., et al. (2007), Remote-sensing measurements in the polar vortex: Comparison to in situ observations and implications for the simultaneous retrievals and analysis of the NO 2 and OClO species,

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Balloon-borne observations of mid-latitude stratospheric water vapour: comparisons with HALOE and MLS satellite data

et al. 2013

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International audienceWe present here in situ measurements obtained between 1991 and 2011 in outervortexconditions by the ELHYSA balloon-borne frost-point hygrometer. The frost-point hygrometerprofiles are used for comparisons with the satellite data from version 19 (v19) andversion 3.3 (v3.3) of the HALogen Occultation Experiment (HALOE) and theMicrowave LimbSounder (MLS) respectively. Potential Vorticity mapping is applied to all data sets to removecontributions of transient tropical intrusions and polar vortex air masses and hence ensureconsistent comparisons between the balloon and satellite observations. Our selected balloon insitu observations are too sparse to directly infer mid-latitude stratospheric time series forcontinuous comparisons with HALOE and MLS records or derive water vapour trends but canbe used to validate the satellite data. A mean difference of −0.83±1.58 % (−0.04±0.07 ppmv) isobtained between HALOE v19 data and the balloon frost-point observations (with respect toHALOE) over the 30–80 hPa altitude range. The hygrometer-HALOE differences appear timedependentas already presented in the literature. The mean difference reaches 2.80±0.96 %(0.13±0.04 ppmv) forMLS v3.3,withMLS systematically wetter than the balloon data reflectinga systematic bias between both datasets. We use our balloon data as reference to provide someinformation about the HALOE-MLS difference. From post-2000 ELHYSA-HALOE andELHYSA-MLS comparisons, we find a HALOE-MLS difference matching the expected bias,with MLS v3.3 6.60±2.80 % (0.27±0.11 ppmv) wetter than HALOE v19. From the results obtained from our balloon-satellite data comparisons, we finally discuss the issue about mergingthe HALOE and MLS data sets to provide stratospheric water vapour trends

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Comparison of high-latitude line-of-sight ozone column density with derived ozone fields and the effects of horizontal inhomogeneity

Cited by 5 publications

References 23 publications

Impact of temperature field inhomogeneities on the retrieval of atmospheric species from MIPAS IR limb emission spectra

Impact of temperature field inhomogeneities on the retrieval of atmospheric species from MIPAS IR limb emission spectra

Remote‐sensing measurements in the polar vortex: Comparison to in situ observations and implications for the simultaneous retrievals and analysis of the NO₂ and OClO species

Balloon-borne observations of mid-latitude stratospheric water vapour: comparisons with HALOE and MLS satellite data

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Comparison of high-latitude line-of-sight ozone column density with derived ozone fields and the effects of horizontal inhomogeneity

Cited by 5 publications

References 23 publications

Impact of temperature field inhomogeneities on the retrieval of atmospheric species from MIPAS IR limb emission spectra

Impact of temperature field inhomogeneities on the retrieval of atmospheric species from MIPAS IR limb emission spectra

Remote‐sensing measurements in the polar vortex: Comparison to in situ observations and implications for the simultaneous retrievals and analysis of the NO2 and OClO species

Balloon-borne observations of mid-latitude stratospheric water vapour: comparisons with HALOE and MLS satellite data

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Remote‐sensing measurements in the polar vortex: Comparison to in situ observations and implications for the simultaneous retrievals and analysis of the NO₂ and OClO species