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  • 1
    Online Resource
    Online Resource
    An idealized stratospheric model useful for understanding differences between long‐lived trace gas measurements and global chemistry‐climate model output
    American Geophysical Union (AGU) ; 2016
    In:  Journal of Geophysical Research: Atmospheres Vol. 121, No. 10 ( 2016-05-27), p. 5356-5367
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 121, No. 10 ( 2016-05-27), p. 5356-5367
    Abstract: Idealized stratospheric model accurately simulates CMAM trace gas and mean age profiles Idealized model provides quantitative transport guidance for CCM to better simulate observations Specific suite of trace gas measurements provides unique transport information to validate CCMs
    Type of Medium: Online Resource
    ISSN: 2169-897X , 2169-8996
    URL: Issue
    URL: Article
    DOI: 10.1002/jgrd.v121.10
    DOI: 10.1002/2015JD024447
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2016
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  • 2
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    Assessing stratospheric transport in the CMAM30 simulations using ACE-FTS measurements
    Copernicus GmbH ; 2018
    In:  Atmospheric Chemistry and Physics Vol. 18, No. 9 ( 2018-05-16), p. 6801-6828
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 18, No. 9 ( 2018-05-16), p. 6801-6828
    Abstract: Abstract. Stratospheric transport in global circulation models and chemistry–climate models is an important component in simulating the recovery of the ozone layer as well as changes in the climate system. The Brewer–Dobson circulation is not well constrained by observations and further investigation is required to resolve uncertainties related to the mechanisms driving the circulation. This study has assessed the specified dynamics mode of the Canadian Middle Atmosphere Model (CMAM30) by comparing to the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) profile measurements of CFC-11 (CCl3F), CFC-12 (CCl2F2), and N2O. In the CMAM30 specified dynamics simulation, the meteorological fields are nudged using the ERA-Interim reanalysis and a specified tracer was employed for each species, with hemispherically defined surface measurements used as the boundary condition. A comprehensive sampling technique along the line of sight of the ACE-FTS measurements has been utilized to allow for direct comparisons between the simulated and measured tracer concentrations. The model consistently overpredicts tracer concentrations of CFC-11, CFC-12, and N2O in the lower stratosphere, particularly in the northern hemispheric winter and spring seasons. The three mixing barriers investigated, including the polar vortex, the extratropical tropopause, and the tropical pipe, show that there are significant inconsistencies between the measurements and the simulations. In particular, the CMAM30 simulation underpredicts mixing efficiency in the tropical lower stratosphere during the June–July–August season.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    DOI: 10.5194/acp-18-6801-2018
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2018
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  • 3
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    Solar occultation satellite data and derived meteorological products: Sampling issues and comparisons with Aura Microwave Limb Sounder
    American Geophysical Union (AGU) ; 2007
    In:  Journal of Geophysical Research Vol. 112, No. D24 ( 2007-12-25)
    Details
    In: Journal of Geophysical Research, American Geophysical Union (AGU), Vol. 112, No. D24 ( 2007-12-25)
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2007JD008709
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2007
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    detail.hit.zdb_id: 2969341-X
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    detail.hit.zdb_id: 3094268-8
    detail.hit.zdb_id: 710256-2
    detail.hit.zdb_id: 2016804-4
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    detail.hit.zdb_id: 3094219-6
    detail.hit.zdb_id: 3094167-2
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  • 4
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    Millimetre wave spectrum of the weakly bound complex NH 3 -N 2
    Informa UK Limited ; 2001
    In:  Molecular Physics Vol. 99, No. 16 ( 2001-08-20), p. 1391-1396
    Details
    In: Molecular Physics, Informa UK Limited, Vol. 99, No. 16 ( 2001-08-20), p. 1391-1396
    Type of Medium: Online Resource
    ISSN: 0026-8976 , 1362-3028
    URL: Article
    DOI: 10.1080/00268970110061801
    Language: English
    Publisher: Informa UK Limited
    Publication Date: 2001
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  • 5
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    Infrared and millimeter wave spectra of the CH4–CO complex in the A internal rotation state
    AIP Publishing ; 2001
    In:  The Journal of Chemical Physics Vol. 114, No. 11 ( 2001-03-15), p. 4824-4828
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 114, No. 11 ( 2001-03-15), p. 4824-4828
    Abstract: The weakly bound van der Waals complex CH4–CO has been observed spectroscopically for the first time in the infrared (C–O stretching, ≈2143 cm−1) and millimeter wave (80–107 GHz) regions. The spectra analyzed here resemble quite closely those of the rare gas–carbon monoxide complexes, like Ne–CO and Ar–CO, and they almost certainly arise from CH4–CO complexes composed of CH4 in the lowest j=0 rotational state of A symmetry. The effective ground state intermolecular separation is 3.994 Å. Predictions are given here for the K=0 and 1 pure rotational microwave transitions of CH4–CO in the A state. The infrared spectrum shows numerous additional transitions which must be due to CH4–CO composed of methane in the F and E symmetry states, but these have not yet been assigned. Future microwave measurements on these F and E states will aid further progress on the infrared spectrum.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.1349425
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2001
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  • 6
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    Assessment of the quality of ACE-FTS stratospheric ozone data
    Copernicus GmbH ; 2022
    In:  Atmospheric Measurement Techniques Vol. 15, No. 5 ( 2022-03-09), p. 1233-1249
    Details
    In: Atmospheric Measurement Techniques, Copernicus GmbH, Vol. 15, No. 5 ( 2022-03-09), p. 1233-1249
    Abstract: Abstract. For the past 17 years, the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) instrument on the Canadian SCISAT satellite has been measuring profiles of atmospheric ozone. The latest operational versions of the level 2 ozone data are versions 3.6 and 4.1. This study characterizes how both products compare with correlative data from other limb-sounding satellite instruments, namely MAESTRO, MLS, OSIRIS, SABER, and SMR. In general, v3.6, with respect to the other instruments, exhibits a smaller bias (which is on the order of ∼ 3 %) in the middle stratosphere than v4.1 (∼ 2 %–9 %); however, the bias exhibited in the v4.1 data tends to be more stable, i.e. not changing significantly over time in any altitude region. In the lower stratosphere, v3.6 has a positive bias of about 3 %–5 % that is stable to within ±1 % per decade, and v4.1 has a bias on the order of −1 % to +5 % and is also stable to within ±1 % per decade. In the middle stratosphere, v3.6 has a positive bias of ∼ 3 % with a significant negative drift on the order of 0.5 %–2.5 % per decade, and v4.1 has a positive bias of 2 %–9 % that is stable to within ±0.5 % per decade. In the upper stratosphere, v3.6 has a positive bias that increases with altitude up to ∼ 16 % and a significant negative drift on the order of 2 %–3 % per decade, and v4.1 has a positive bias that increases with altitude up to ∼ 15 % and is stable to within ±1 % per decade. Estimates indicate that both versions 3.6 and 4.1 have precision values on the order of 0.1–0.2 ppmv below 20 km and above 45 km (∼ 5 %–10 %, depending on altitude). Between 20 and 45 km, the estimated v3.6 precision of ∼ 4 %–6 % is better than the estimated v4.1 precision of ∼ 6 %–10 %.
    Type of Medium: Online Resource
    ISSN: 1867-8548
    URL: Article
    DOI: 10.5194/amt-15-1233-2022
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2022
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  • 7
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    Evaluation of ACE-FTS and OSIRIS Satellite retrievals of ozone and nitric acid in the tropical upper troposphere: Application to ozone production efficiency
    American Geophysical Union (AGU) ; 2011
    In:  Journal of Geophysical Research Vol. 116, No. D12 ( 2011-06-29)
    Details
    In: Journal of Geophysical Research, American Geophysical Union (AGU), Vol. 116, No. D12 ( 2011-06-29)
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2010JD015056
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2011
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    SSG: 16,13
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  • 8
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    Characterizing model errors in chemical transport modeling of methane: impact of model resolution in versions v9-02 of GEOS-Chem and v35j of its adjoint model
    Copernicus GmbH ; 2020
    In:  Geoscientific Model Development Vol. 13, No. 9 ( 2020-08-31), p. 3839-3862
    Details
    In: Geoscientific Model Development, Copernicus GmbH, Vol. 13, No. 9 ( 2020-08-31), p. 3839-3862
    Abstract: Abstract. The GEOS-Chem simulation of atmospheric CH4 was evaluated against observations from the Thermal and Near Infrared Sensor for Carbon Observations Fourier Transform Spectrometer (TANSO-FTS) on the Greenhouse Gases Observing Satellite (GOSAT), the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS), and the Total Carbon Column Observing Network (TCCON). We focused on the model simulations at the 4∘×5∘ and 2∘×2.5∘ horizontal resolutions for the period of February–May 2010. Compared to the GOSAT, TCCON, and ACE-FTS data, we found that the 2∘×2.5∘ model produced a better simulation of CH4, with smaller biases and a higher correlation to the independent data. We found large resolution-dependent differences such as a latitude-dependent XCH4 bias, with higher column abundances of CH4 at high latitudes and lower abundances at low latitudes at the 4∘×5∘ resolution than at 2∘×2.5∘. We also found large differences in CH4 column abundances between the two resolutions over major source regions such as China. These differences resulted in up to 30 % differences in inferred regional CH4 emission estimates from the two model resolutions. We performed several experiments using 222Rn, 7Be, and CH4 to determine the origins of the resolution-dependent errors. The results suggested that the major source of the latitude-dependent errors is excessive mixing in the upper troposphere and lower stratosphere, including mixing at the edge of the polar vortex, which is pronounced at the 4∘×5∘ resolution. At the coarser resolution, there is weakened vertical transport in the troposphere at midlatitudes to high latitudes due to the loss of sub-grid tracer eddy mass flux in the storm track regions. The vertical air mass fluxes are calculated in the model from the degraded coarse-resolution wind fields and the model does not conserve the air mass flux between model resolutions; as a result, the low resolution does not fully capture the vertical transport. This produces significant localized discrepancies, such as much greater CH4 abundances in the lower troposphere over China at 4∘×5∘ than at 2∘×2.5∘. Although we found that the CH4 simulation is significantly better at 2∘×2.5∘ than at 4∘×5∘, biases may still be present at 2∘×2.5∘ resolution. Their importance, particularly in regards to inverse modeling of CH4 emissions, should be evaluated in future studies using online transport in the native general circulation model as a benchmark simulation.
    Type of Medium: Online Resource
    ISSN: 1991-9603
    URL: Article
    DOI: 10.5194/gmd-13-3839-2020
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2020
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  • 9
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    Characterizing model errors in chemical transport modeling of methane: using GOSAT XCH〈sub〉4〈/sub〉 data with weak-constraint four-dimensional variational data assimilation
    Copernicus GmbH ; 2021
    In:  Atmospheric Chemistry and Physics Vol. 21, No. 12 ( 2021-06-24), p. 9545-9572
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 21, No. 12 ( 2021-06-24), p. 9545-9572
    Abstract: Abstract. We examined biases in the global GEOS-Chem chemical transport model for the period of February–May 2010 using weak-constraint (WC) four-dimensional variational (4D-Var) data assimilation and dry-air mole fractions of CH4 (XCH4) from the Greenhouse gases Observing SATellite (GOSAT). The ability of the observations and the WC 4D-Var method to mitigate model errors in CH4 concentrations was first investigated in a set of observing system simulation experiments (OSSEs). We then assimilated the GOSAT XCH4 retrievals and found that they were capable of providing information on the vertical structure of model errors and of removing a significant portion of biases in the modeled CH4 state. In the WC 4D-Var assimilation, corrections were added to the modeled CH4 state at each model time step to account for model errors and improve the model fit to the assimilated observations. Compared to the conventional strong-constraint (SC) 4D-Var assimilation, the WC method was able to significantly improve the model fit to independent observations. Examination of the WC state corrections suggested that a significant source of model errors was associated with discrepancies in the model CH4 in the stratosphere. The WC state corrections also suggested that the model vertical transport in the troposphere at middle and high latitudes is too weak. The problem was traced back to biases in the uplift of CH4 over the source regions in eastern China and North America. In the tropics, the WC assimilation pointed to the possibility of biased CH4 outflow from the African continent to the Atlantic in the mid-troposphere. The WC assimilation in this region would greatly benefit from glint observations over the ocean to provide additional constraints on the vertical structure of the model errors in the tropics. We also compared the WC assimilation at 4∘ × 5∘ and 2∘ × 2.5∘ horizontal resolutions and found that the WC corrections to mitigate the model errors were significantly larger at 4∘ × 5∘ than at 2∘ × 2.5∘ resolution, indicating the presence of resolution-dependent model errors. Our results illustrate the potential utility of the WC 4D-Var approach for characterizing model errors. However, a major limitation of this approach is the need to better characterize the specified model error covariance in the assimilation scheme.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    DOI: 10.5194/acp-21-9545-2021
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2021
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  • 10
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    Validation of ozone profile retrievals derived from the OMPS LP version 2.5 algorithm against correlative satellite measurements
    Copernicus GmbH ; 2018
    In:  Atmospheric Measurement Techniques Vol. 11, No. 5 ( 2018-05-16), p. 2837-2861
    Details
    In: Atmospheric Measurement Techniques, Copernicus GmbH, Vol. 11, No. 5 ( 2018-05-16), p. 2837-2861
    Abstract: Abstract. The Limb Profiler (LP) is a part of the Ozone Mapping and Profiler Suite launched on board of the Suomi NPP satellite in October 2011. The LP measures solar radiation scattered from the atmospheric limb in ultraviolet and visible spectral ranges between the surface and 80 km. These measurements of scattered solar radiances allow for the retrieval of ozone profiles from cloud tops up to 55 km. The LP started operational observations in April 2012. In this study we evaluate more than 5.5 years of ozone profile measurements from the OMPS LP processed with the new NASA GSFC version 2.5 retrieval algorithm. We provide a brief description of the key changes that had been implemented in this new algorithm, including a pointing correction, new cloud height detection, explicit aerosol correction and a reduction of the number of wavelengths used in the retrievals. The OMPS LP ozone retrievals have been compared with independent satellite profile measurements obtained from the Aura Microwave Limb Sounder (MLS), Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) and Odin Optical Spectrograph and InfraRed Imaging System (OSIRIS). We document observed biases and seasonal differences and evaluate the stability of the version 2.5 ozone record over 5.5 years. Our analysis indicates that the mean differences between LP and correlative measurements are well within required ±10 % between 18 and 42 km. In the upper stratosphere and lower mesosphere (〉 43 km) LP tends to have a negative bias. We find larger biases in the lower stratosphere and upper troposphere, but LP ozone retrievals have significantly improved in version 2.5 compared to version 2 due to the implemented aerosol correction. In the northern high latitudes we observe larger biases between 20 and 32 km due to the remaining thermal sensitivity issue. Our analysis shows that LP ozone retrievals agree well with the correlative satellite observations in characterizing vertical, spatial and temporal ozone distribution associated with natural processes, like the seasonal cycle and quasi-biennial oscillations. We found a small positive drift ∼ 0.5 % yr−1 in the LP ozone record against MLS and OSIRIS that is more pronounced at altitudes above 35 km. This pattern in the relative drift is consistent with a possible 100 m drift in the LP sensor pointing detected by one of our altitude-resolving methods.
    Type of Medium: Online Resource
    ISSN: 1867-8548
    URL: Article
    URL: Article
    DOI: 10.5194/amt-11-2837-2018
    DOI: 10.5194/amt-11-2837-2018-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2018
    detail.hit.zdb_id: 2505596-3
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