Retrieval of stratospheric aerosol size information from OSIRIS limb scattered sunlight spectra

Bourassa, A. E.; Degenstein, D. A.; Llewellyn, E. J.

doi:10.5194/acp-8-6375-2008

Cited by 48 publications

(59 citation statements)

References 23 publications

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“…The imager channels at 1260 and 1270 nm were designed to measure excited-state oxygen emission, and this emission renders these channels unusable for aerosol retrieval; however, the 1530 nm channel, which was designed to measure an excited OH emission that is extremely weak during daytime, can be used for the aerosol retrieval. A proof-of-concept particle size retrieval using a combination of OSIRIS spectral measurements and a simple two-step retrieval is presented in Bourassa et al (2008a). A different algorithm which assumes a constant size profile is presented by Rault and Loughman (2013) for use with the OMPS data.…”

Section: Osiris Information Contentmentioning

confidence: 99%

Stratospheric aerosol particle size information in Odin-OSIRIS limb scatter spectra

2014

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Abstract. The Optical Spectrograph and InfraRed Imaging System (OSIRIS) onboard the Odin satellite has now taken over a decade of limb scatter measurements that have been used to retrieve the version 5 stratospheric aerosol extinction product. This product is retrieved using a representative particle size distribution to calculate scattering cross sections and scattering phase functions for the forward model calculations. In this work the information content of OSIRIS measurements with respect to stratospheric aerosol is systematically examined for the purpose of retrieving particle size information along with the extinction coefficient. The benefit of using measurements at different wavelengths and scattering angles in the retrieval is studied, and it is found that incorporation of the 1530 nm radiance measurement is key for a robust retrieval of particle size information. It is also found that using OSIRIS measurements at the different solar geometries available on the Odin orbit simultaneously provides little additional benefit. Based on these results, an improved aerosol retrieval algorithm is developed that couples the retrieval of aerosol extinction and mode radius of a log-normal particle size distribution. Comparison of these results with coincident measurements from SAGE III shows agreement in retrieved extinction to within approximately 10 % over the bulk of the aerosol layer, which is comparable to version 5. The retrieved particle size, when converted to Ångström coefficient, shows good qualitative agreement with SAGE II measurements made at somewhat shorter wavelengths.

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Section: Osiris Information Contentmentioning

confidence: 99%

Stratospheric aerosol particle size information in Odin-OSIRIS limb scatter spectra

2014

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“…Ozone number density profiles are retrieved from the cloud tops to 60 km (down to a minimum of 10 km in the absence of clouds) using a combination of ozone absorption information in the UV and visible parts of the spectrum. Aerosol and NO 2 are also retrieved with ozone to reduce biases (Bourassa et al, , 2008a(Bourassa et al, , 2011. SaskMART v5.0x ozone has an estimated precision of 3-4 % in the middle stratosphere (Bourassa et al, 2012b) and a vertical resolution of ∼ 2 km at low altitudes and in the middle stratosphere, with decreasing resolution toward higher altitudes, reaching ∼ 3 km at 50 km altitude.…”

Section: The Osiris Ozone Data Set From 2001 To the Presentmentioning

confidence: 99%

Assessment of Odin-OSIRIS ozone measurements from 2001 to the present using MLS, GOMOS, and ozonesondes

et al. 2014

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Abstract. The Optical Spectrograph and InfraRed Imaging System (OSIRIS) was launched aboard the Odin satellite in 2001 and is continuing to take limb-scattered sunlight measurements of the atmosphere. This work aims to characterize and assess the stability of the OSIRIS 11 yr v5.0x ozone data set. Three validation data sets were used: the v2.2 Microwave Limb Sounder (MLS) and v6 Global Ozone Monitoring by Occultation of Stars (GOMOS) satellite data records, and ozonesonde measurements. Global mean percent differences between coincident OSIRIS and validation measurements are within 5 % at all altitudes above 18.5 km for MLS, above 21.5 km for GOMOS, and above 17.5 km for ozonesondes. Below 17.5 km, OSIRIS measurements agree with ozonesondes within 5 % and are well-correlated (R > 0.75) with them. For low OSIRIS optics temperatures (< 16 • C), OSIRIS ozone measurements have a negative bias of 1-6 % compared with the validation data sets for 25.5-40.5 km. Biases between OSIRIS ascending and descending node measurements were investigated and found to be related to aerosol retrievals below 27.5 km. Above 30 km, agreement between OSIRIS and the validation data sets was related to the OSIRIS retrieved albedo, which measures apparent upwelling, with a positive bias in OSIRIS data with large albedos. In order to assess the long-term stability of OSIRIS measurements, global average drifts relative to the validation data sets were calculated and were found to be < 3 % per decade for comparisons with MLS for 19.5-36.5 km, GOMOS for 18.5-54.5 km, and ozonesondes for 12.5-22.5 km. Above 36.5 km, the relative drift for OSIRIS versus MLS ranged from ∼ 0 to 6 % per decade, depending on the data set used to convert MLS data to the OSIRIS altitude versus number density grid. Overall, this work demonstrates that the OSIRIS 11 yr ozone data set from 2001 to the present is suitable for trend studies.

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“…Several studies have shown the capability for the retrieval of vertical profiles of stratospheric aerosol parameters from measurements of the limb radiance at visible and near infrared wavelengths (Bourassa et al, 2007(Bourassa et al, , 2008bRault and Loughman, 2007;Tukiainen et al, 2008). The limb scatter measurement technique has a distinct benefit over occultation in terms of sampling; vertical profiles can be obtained repetitively for tangent points in the sunlit hemisphere providing nearly global coverage within a relatively short time period.…”

Section: Introductionmentioning

confidence: 99%

Odin-OSIRIS stratospheric aerosol data product and SAGE III intercomparison

et al. 2012

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Abstract. The scattered sunlight measurements made by the Optical Spectrograph and InfraRed Imaging System (OSIRIS) on the Odin spacecraft are used to retrieve vertical profiles of stratospheric aerosol extinction at 750 nm. The recently released OSIRIS Version 5 data product contains the first publicly released stratospheric aerosol extinction retrievals, and these are now available for the entire Odin mission, which extends from the present day back to launch in 2001. A proof-of-concept study for the retrieval of stratospheric aerosol extinction from limb scatter measurements was previously published and the Version 5 data product retrievals are based on this work, but incorporate several important improvements to the algorithm. One of the primary changes is the use of a new retrieval vector that greatly improves the sensitivity to aerosol scattering by incorporating a forward modeled calculation of the radiance from a Rayleigh atmosphere. Additional improvements include a coupled retrieval of the effective albedo, a new method for normalization of the retrieval vector to improve signal-to-noise, and the use of an initial guess that is representative of very low background aerosol loading conditions, which allows for maximal retrieval range. Furthermore, the Version 5 data set is compared to Stratospheric Aerosol and Gas Experiment (SAGE) III 755 nm extinction profiles during the almost four years of mission overlap from 2002 to late 2005. The vertical structure in coincident profile measurements is well correlated and the statistics on a relatively large set of tight coincident measurements show agreement between the measurements from the two instruments to within approximately 10 % throughout the 15 to 25 km altitude range, which covers the bulk of the stratospheric aerosol layer for the mid and high latitude cases studied here.

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Retrieval of stratospheric aerosol size information from OSIRIS limb scattered sunlight spectra

Cited by 48 publications

References 23 publications

Stratospheric aerosol particle size information in Odin-OSIRIS limb scatter spectra

Stratospheric aerosol particle size information in Odin-OSIRIS limb scatter spectra

Assessment of Odin-OSIRIS ozone measurements from 2001 to the present using MLS, GOMOS, and ozonesondes

Odin-OSIRIS stratospheric aerosol data product and SAGE III intercomparison

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