Precision estimate for Odin‐OSIRIS limb scatter retrievals

Bourassa, A. E.; McLinden, Chris A.; Bathgate, A. F.; Elash, B. J.; Degenstein, D. A.

doi:10.1029/2011jd016976

Cited by 26 publications

(23 citation statements)

References 27 publications

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“…The natural variability within the space-time collocation window is small but not zero. This results in additional difficulties in the application of this method, as observed by Bourassa et al (2012). The small-scale natural variability also disturbs application of the Method 1.…”

Section: Methodsmentioning

confidence: 99%

“…(3) is reduced to s 2 12 ≈ 2σ 2 , thus allowing validation of the uncertainty estimate σ . This method was realized, for example, for closely collocated MIPAS and OSIRIS measurements (Bourassa et al, 2012;Piccolo and Dudhia, 2007). The uncertainty of this experimental precision estimateσ 2 = s 2 12 /2 is defined by the uncertainty of sample variance s 2 12 .…”

Section: Methodsmentioning

confidence: 99%

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Validation of GOMOS ozone precision estimates in the stratosphere

et al. 2014

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Abstract. Accurate information about uncertainties is required in nearly all data analyses, e.g., inter-comparisons, data assimilation, combined use. Validation of precision estimates (viz., the random component of estimated uncertainty) is important for remote sensing measurements, which provide the information about atmospheric parameters by solving an inverse problem. For the Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument, this is a real challenge, due to the dependence of the signal-to-noise ratio (and thus precision estimates) on stellar properties, small number of self-collocated measurements, and growing noise as a function of time due to instrument aging. The estimated ozone uncertainties are small in the stratosphere for bright star occultations, which complicates validation of precision values, given the natural ozone variability.In this paper, we discuss different methods for geophysical validation of precision estimates and their applicability to GOMOS data. We propose a simple method for validation of GOMOS precision estimates for ozone in the stratosphere. This method is based on comparisons of differences in sample variance with differences in uncertainty estimates for measurements from different stars selected in a region of small natural variability.For GOMOS, the difference in sample variances for different stars at tangent altitudes 25-45 km is well explained by the difference in squared precisions, if the stars are not dim. Since this is observed for several stars, and since normalized χ 2 is close to 1 for these occultations in the stratosphere, we conclude that the GOMOS precision estimates are realistic in occultations of sufficiently bright stars. For dim stars, errors are overestimated due to improper accounting of the dark charge correction uncertainty in the error budget. The proposed method can also be applied to stratospheric ozone data from other instruments, including multi-instrument analyses.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Validation of GOMOS ozone precision estimates in the stratosphere

et al. 2014

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“…The newly validated version 5 (V5) of the OSIRIS aerosol extinction retrievals at 750 nm (Bourassa et al, 2012b) is used in this study. The estimated error of V5 extinction is of 10-15 % in the mid-stratosphere (Bourassa et al, 2012c).…”

Section: Satellite-borne Observationsmentioning

confidence: 99%

Stratospheric aerosols from the Sarychev volcano eruption in the 2009 Arctic summer

et al. 2013

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Aerosols from the Sarychev volcano eruption (Kuril Islands, northeast of Japan) were observed in the Arctic lower stratosphere a few days after the strongest SO₂ injection which occurred on 15 and 16 June 2009. From the observations provided by the Infrared Atmospheric Sounding Interferometer (IASI) an estimated 0.9 Tg of sulphur dioxide was injected into the upper troposphere and lower stratosphere (UTLS). The resultant stratospheric sulphate aerosols were detected from satellites by the Optical Spectrograph and Infrared Imaging System (OSIRIS) limb sounder and by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and from the surface by the Network for the Detection of Atmospheric Composition Changes (NDACC) lidar deployed at OHP (Observatoire de Haute-Provence, France). By the first week of July the aerosol plume had spread out over the entire Arctic region. The Sarychev-induced stratospheric aerosol over the Kiruna region (north of Sweden) was measured by the Stratospheric and Tropospheric Aerosol Counter (STAC) during eight balloon flights planned in August and September 2009. During this balloon campaign the Micro Radiomètre Ballon (MicroRADIBAL) and the Spectroscopie d'Absorption Lunaire pour l'Observation des Minoritaires Ozone et NOx (SALOMON) remote-sensing instruments also observed these aerosols. Aerosol concentrations returned to near-background levels by spring 2010. The effective radius, the surface area density (SAD), the aerosol extinction, and the total sulphur mass from STAC in situ measurements are enhanced with mean values in the range 0.15–0.21 μm, 5.5–14.7 μm² cm⁻³, 5.5–29.5 × 10⁻⁴ km⁻¹, and 4.9–12.6 × 10⁻¹⁰ kg[S] kg⁻¹[air], respectively, between 14 km and 18 km. The observed and modelled e-folding time of sulphate aerosols from the Sarychev eruption is around 70–80 days, a value much shorter than the 12–14 months calculated for aerosols from the 1991 eruption of Mt Pinatubo. The OSIRIS stratospheric aerosol optical depth (AOD) at 750 nm is enhanced by a factor of 6, with a value of 0.02 in late July compared to 0.0035 before the eruption. The HadGEM2 and MIMOSA model outputs indicate that aerosol layers in polar region up to 14–15 km are largely modulated by stratosphere–troposphere exchange processes. The spatial extent of the Sarychev plume is well represented in the HadGEM2 model with lower altitudes of the plume being controlled by upper tropospheric troughs which displace the plume downward and upper altitudes around 18–20 km, in agreement with lidar observations. Good consistency is found between the HadGEM2 sulphur mass density and the value inferred from the STAC observations, with a maximum located about 1 km above the tropopause ranging from 1 to 2 × 10⁻⁹ kg[S] kg⁻¹[air], which is one order of magnitude higher than the background level

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“…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. OSIRIS ozone data were filtered for outliers according to the techniques described by Adams et al (2013).…”

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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Precision estimate for Odin‐OSIRIS limb scatter retrievals

Cited by 26 publications

References 27 publications

Validation of GOMOS ozone precision estimates in the stratosphere

Validation of GOMOS ozone precision estimates in the stratosphere

Stratospheric aerosols from the Sarychev volcano eruption in the 2009 Arctic summer

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

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