scholarly journals Monitoring of Trace Gases over Antarctic by GaoFen-5/AIUS: Algorithm Description and First Retrieval Results of O3 , H2O and HCl

2019 ◽  
Author(s):  
Xiaoying Li ◽  
Tianhai Cheng ◽  
Jian Xu ◽  
Hailiang Shi ◽  
Pengmei Wang ◽  
...  
Keyword(s):  
Spectral Range ◽  
Spectral Resolution ◽  
Trace Gases ◽  
Relative Difference ◽  
Chemical Processes ◽  
Trace Gas ◽  
Retrieval Algorithm ◽  
Upper Troposphere ◽  
Level 2 ◽  
Good Agreement

AIUS (Atmospheric Infrared Ultraspectral Sounder) is an infrared occultation spectrometer onboard the Chinese GaoFen-5 satellite, which covers a spectral range of 2.4--13.3 μm (750--4100 cm-1) with a spectral resolution of about 0.02 cm-1. AIUS was designed to measure and to study chemical processes of ozone (O3) and other trace gases in the upper troposphere and stratosphere over Antarctic. In this study, the corresponding retrieval methodology is described. The comparison between AIUS measurements and simulated spectra illustrates that AIUS measurements agree well to the simulated spectra. To first evaluate the reliability of our retrieval algorithm, three retrieval O3 experiments are performed based on ACE-FTS observation spectra. A comparison between our retrieved profiles and the ACE-FTS official products shows that the relative difference of these three retrieval experiments is mostly within 10% between 20 km and 70 km. These retrieval experiments demonstrate that the retrieval algorithm described in this study work fine and reliable. Furthermore, O3, H2O and HCl profiles are retrieved from eight orbits of AIUS measurements and compared with the official AURA/MLS level-2 v4.2 profiles. Comparison experiments show that the relative difference is mostly within 10% (about 0.02 - 0.4 ppm) between 18 and 58 km for O3 retrieval, within 10% (0-0.5 ppm) between 15 and 80 km for H2O retrieval, and within 10% (about 0.1 ppb) between 30 and 60 km for HCl retrieval. There is a good agreement in the retrieved trace gas profiles obtained from AIUS and from coincident profiles from MLS.

scholarly journals Monitoring Trace Gases over the Antarctic Using Atmospheric Infrared Ultraspectral Sounder Onboard GaoFen-5: Algorithm Description and First Retrieval Results of O3, H2O, and HCl

2019 ◽  
Vol 11 (17) ◽  
pp. 1991 ◽  
Author(s):  
Xiaoying Li ◽  
Jian Xu ◽  
Tianhai Cheng ◽  
Hailiang Shi ◽  
Xingying Zhang ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Trace Gases ◽  
Relative Difference ◽  
Trace Gas ◽  
Retrieval Algorithm ◽  
Upper Troposphere ◽  
The Antarctic ◽  
Chemistry Experiment ◽  
Level 2 ◽  
Good Agreement

AIUS (Atmospheric Infrared Ultraspectral Sounder) is an infrared occultation spectrometer onboard the Chinese GaoFen-5 satellite, which covers a spectral range of 2.4–13.3 μm (750–4100 cm−1) with a spectral resolution of about 0.02 cm−1. AIUS was designed to measure and to study the chemical processes of ozone (O3) and other trace gases in the upper troposphere and stratosphere over the Antarctic. In this study, the AIUS retrieval methodology is described. A comparison between AIUS measurements and simulated spectra illustrates that AIUS measurements agree well with the simulated spectra. To first evaluate the reliability of the AIUS retrieval algorithm, three retrieval O3 experiments were performed based on ACE-FTS (Atmospheric Chemistry Experiment—Fourier transform spectrometer) observed spectra. A comparison with the ACE-FTS official products shows that the relative difference of these three retrieval experiments was mostly within 10% between 20 and 70 km. These retrieval experiments demonstrate that the retrieval algorithm described in this study provided reliable results and reliably. Furthermore, O3, H2O, and HCl profiles were retrieved from 24 orbits of AIUS measurements and compared with the official Aura /MLS (Microwave Limb Sounder) level-2 v4.2 profiles. The relative difference was mostly within 10% (about 0.02–0.4 ppm) between 18 and 58 km for the O3 retrieval, within 10% (0–0.5 ppm) between 15 and 80 km for the H2O retrieval, and within 10% (about 0.1 ppb) between 30 and 60 km for the HCl retrieval. A good agreement in the retrieved trace gas profiles was reached between AIUS and MLS.

scholarly journals Trace Gas Retrieval from AIUS：Algorithm Description and O3 Retrieval Assessment

2018 ◽  
Author(s):  
Xiaoying Li ◽  
Tianhai Cheng ◽  
Jian Xu ◽  
Hailiang Shi ◽  
Xingying Zhang ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Measurement Errors ◽  
A Priori ◽  
Relative Difference ◽  
Trace Gas ◽  
Model Parameters ◽  
Upper Troposphere ◽  
True Profile ◽  
Chemistry Experiment ◽  
Level 2

AIUS (Atmospheric Infrared Ultraspectral Sounder) is an infrared occultation spectrometer onboard the Chinese GaoFen-5 satellite, which covers a spectral range of 2.4–13.3 μm (750–4100 cm−1) with a spectral resolution of about 0.02 cm−1. AIUS is designed to measure and study chemical processes of ozone (O3) and other trace gases in the upper troposphere and stratosphere around Antarctic. In this study, the corresponding retrieval methodology is described. The retrieval simulations based on the simulated spectra of AIUS have been carried out, with a focus on O3. The relative difference between the retrieved and the true O3 profiles is within 5% from the 15 km to 70 km and about 10% below 15 km. The corresponding averaging kernels illustrate that the overall retrieval information mainly come from the spectra, not the a priori. The retrieval experiments also demonstrate that the shape of the retrieved profiles resembles the shape of the true profile even if the shape of the a priori profile is different from that of the true profile. Further, we perform the O3 retrieval from the real ACE-FTS (Atmospheric Chemistry Experiment-Fourier Transform Spectrometer) measurements and compare the results with the official ACE-FTS Level-2 products. Overall, both profiles agree well in the stratosphere where the retrieval sensitivity is high. The relative difference between both profiles is about 15% below 70 km, which may due to the measurement errors and different forward model parameters.

scholarly journals Seasonal characteristics of trace gas transport into the extratropical upper troposphere and lower stratosphere

2019 ◽  
Vol 19 (10) ◽  
pp. 7073-7103 ◽  
Author(s):  
Yoichi Inai ◽  
Ryo Fujita ◽  
Toshinobu Machida ◽  
Hidekazu Matsueda ◽  
Yousuke Sawa ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Trace Gases ◽  
Source Region ◽  
Lower Troposphere ◽  
Trace Gas ◽  
Air Masses ◽  
Backward Trajectories ◽  
Upper Troposphere ◽  
Passive Behavior ◽  
Seasonal Characteristics

Abstract. To investigate the seasonal characteristics of trace gas distributions in the extratropical upper troposphere and lower stratosphere (ExUTLS) as well as stratosphere–troposphere exchange processes, origin fractions of air masses originating in the stratosphere, tropical troposphere, midlatitude lower troposphere (LT), and high-latitude LT in the ExUTLS are estimated using 10-year backward trajectories calculated with European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim data as the meteorological input. Time series of trace gases obtained from ground-based and airborne observations are incorporated into the trajectories, thus reconstructing spatiotemporal distributions of trace gases in the ExUTLS. The reconstructed tracer distributions are analyzed with the origin fractions and the stratospheric age of air (AoA) estimated using the backward trajectories. The reconstructed distributions of SF6 and CO2 in the ExUTLS are linearly correlated with those of AoA because of their chemically passive behavior and quasi-stable increasing trends in the troposphere. Distributions of CH4, N2O, and CO are controlled primarily by chemical decay along the transport path from the source region via the stratosphere and subsequent mixing of such stratospheric air masses with tropospheric air masses in the ExUTLS.

scholarly journals The AERONET Version 3 aerosol retrieval algorithm, associated uncertainties and comparisons to Version 2

2020 ◽  
Author(s):  
Alexander Sinyuk ◽  
Brent N. Holben ◽  
Thomas F. Eck ◽  
David M. Giles ◽  
Ilya Slutsker ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Optical Depth ◽  
Solar Flux ◽  
Gas Absorption ◽  
Retrieval Algorithm ◽  
Dust Aerosols ◽  
Aerosol Retrieval ◽  
Absorbing Aerosols ◽  
Level 2 ◽  
Good Agreement

Abstract. The Aerosol Robotic Network (AERONET) version 3 (V3) aerosol retrieval algorithm is described, which is based on the version 2 (V2) algorithm with numerous updates. Comparisons of V3 aerosol retrievals to those of V2 are presented, along with a new approach to estimate uncertainties in many of the retrieved aerosol parameters. Changes in V3 aerosol retrieval algorithm include: 1) a new polarized radiative transfer code (RTC), which replaced the scalar RTC of V2, 2) detailed characterization of gas absorption by adding NO2 and H2O to specify total gas absorption in the atmospheric column, specification of vertical profiles of all the atmospheric species, 3) new Bidirectional Reflectance Distribution Function (BRDF) parameters for land sites adopted from the MODIS BRDF/Albedo product, 4) a new version of the extraterrestrial solar flux spectrum, and 5) new temperature correction procedure of both direct sun and sky radiance measurements. The potential effect of each change in V3 on single scattering albedo (SSA) retrievals was analyzed. The operational almucantar retrievals of V2 versus V3 were compared for four AERONET sites: GSFC, Mezaira, Mongu, and Kanpur. Analysis showed very good agreement in retrieved parameters of the size distributions. Comparisons of SSA retrievals for dust aerosols (Mezaira) showed a good agreement in 440 nm SSA while for longer wavelengths V3 SSAs are systematically higher than those of V2 with the largest mean difference at 675 nm due to cumulative effects of both extraterrestrial solar flux and BRDF changes. For non-dust aerosols, the largest SSA deviation is at 675 nm due to differences in extraterrestrial solar flux spectrums used in each version. Further, the SSA 675 nm mean differences are very different for weakly (GSFC) and strongly (Mongu) absorbing aerosols which is explained by the lower sensitivity to a bias in aerosol scattering optical depth by less absorbing aerosols. A new hybrid (HYB) sky radiance measurements scan is introduced and discussed. The HYB combines features of scans in two different planes to maximize the range of scattering angles and achieve scan symmetry, thereby allowing for cloud screening and spatial averaging which is an advantage over the principal plane scan that lacks robust symmetry. We show that due to extended range of scattering angles HYB SSA retrievals for dust aerosols exhibit smaller variability with SZA than those of almucantar (ALM) which allows extending HYB SSA retrievals to solar zenith angles (SZA) less than 50° to as small as 25°. The comparison of SSA retrievals from closely time matched HYB and ALM scans in the 50° to 75° SZA range showed good agreement with the differences below ~0.005. We also present an approach to estimate retrieval uncertainties which utilizes the variability in retrieved parameters generated by perturbing both measurements and auxiliary input parameters as a proxy for retrievals uncertainty. The perturbations in measurements and auxiliary inputs are assumed as estimated biases in aerosol optical depth (AOD), radiometric calibration of sky radiances combined with solar spectral irradiance, and surface reflectance. For each set of Level 2 Sun/sky radiometer observations, 27 inputs corresponding to 27 combinations of biases were produced and separately inverted and to generate the following statistics of the inversion results: average, standard deviation, minimum and maximum values. From these statistics standard deviation (labeled as U27) is used as a proxy for estimated uncertainty and a lookup table (LUT) approach was implemented to reduce the computational time. The U27 climatological LUT was generated from the entire AERONET almucantar (1993–2018) and hybrid (2014–2018) scan database by binning U27s in AOD (440 nm), Angstrom Exponent (AE, 440–870nm), and SSA (440, 675, 870, 1020 nm). Using this LUT approach, the uncertainty estimates U27 for each individual V3 Level 2 retrieval can be obtained by interpolation using the corresponding measured and inverted combination of AOD, AE, and SSA.

scholarly journals The AERONET Version 3 aerosol retrieval algorithm, associated uncertainties and comparisons to Version 2

2020 ◽  
Vol 13 (6) ◽  
pp. 3375-3411 ◽  
Author(s):  
Alexander Sinyuk ◽  
Brent N. Holben ◽  
Thomas F. Eck ◽  
David M. Giles ◽  
Ilya Slutsker ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Optical Depth ◽  
Solar Flux ◽  
Gas Absorption ◽  
Retrieval Algorithm ◽  
Dust Aerosols ◽  
Aerosol Retrieval ◽  
Absorbing Aerosols ◽  
Level 2 ◽  
Good Agreement

Abstract. The Aerosol Robotic Network (AERONET) Version 3 (V3) aerosol retrieval algorithm is described, which is based on the Version 2 (V2) algorithm with numerous updates. Comparisons of V3 aerosol retrievals to those of V2 are presented, along with a new approach to estimate uncertainties in many of the retrieved aerosol parameters. Changes in the V3 aerosol retrieval algorithm include (1) a new polarized radiative transfer code (RTC), which replaced the scalar RTC of V2, (2) detailed characterization of gas absorption by adding NO2 and H2O to specify total gas absorption in the atmospheric column, specification of vertical profiles of all the atmospheric species, (3) new bidirectional reflectance distribution function (BRDF) parameters for land sites adopted from the MODIS BRDF/Albedo product, (4) a new version of the extraterrestrial solar flux spectrum, and (5) a new temperature correction procedure of both direct Sun and sky radiance measurements. The potential effect of each change in V3 on single scattering albedo (SSA) retrievals was analyzed. The operational almucantar retrievals of V2 versus V3 were compared for four AERONET sites: GSFC, Mezaira, Mongu, and Kanpur. Analysis showed very good agreement in retrieved parameters of the size distributions. Comparisons of SSA retrievals for dust aerosols (Mezaira) showed a good agreement in 440 nm SSA, while for longer wavelengths V3 SSAs are systematically higher than those of V2, with the largest mean difference at 675 nm due to cumulative effects of both extraterrestrial solar flux and BRDF changes. For non-dust aerosols, the largest SSA deviation is at 675 nm due to differences in extraterrestrial solar flux spectrums used in each version. Further, the SSA 675 nm mean differences are very different for weakly (GSFC) and strongly (Mongu) absorbing aerosols, which is explained by the lower sensitivity to a bias in aerosol scattering optical depth by less absorbing aerosols. A new hybrid (HYB) sky radiance measurement scan is introduced and discussed. The HYB combines features of scans in two different planes to maximize the range of scattering angles and achieve scan symmetry, thereby allowing for cloud screening and spatial averaging, which is an advantage over the principal plane scan that lacks robust symmetry. We show that due to an extended range of scattering angles, HYB SSA retrievals for dust aerosols exhibit smaller variability with solar zenith angles (SZAs) than those of almucantar (ALM), which allows extension of HYB SSA retrievals to SZAs less than 50∘ to as small as 25∘. The comparison of SSA retrievals from closely time-matched HYB and ALM scans in the 50 to 75∘ SZA range showed good agreement with the differences below ∼0.005. We also present an approach to estimate retrieval uncertainties which utilizes the variability in retrieved parameters generated by perturbing both measurements and auxiliary input parameters as a proxy for retrieval uncertainty. The perturbations in measurements and auxiliary inputs are assumed as estimated biases in aerosol optical depth (AOD), radiometric calibration of sky radiances combined with solar spectral irradiance, and surface reflectance. For each set of Level 2 Sun/sky radiometer observations, 27 inputs corresponding to 27 combinations of biases were produced and separately inverted to generate the following statistics of the inversion results: average, standard deviation, minimum and maximum values. From these statistics, standard deviation (labeled U27) is used as a proxy for estimated uncertainty, and a lookup table (LUT) approach was implemented to reduce the computational time. The U27 climatological LUT was generated from the entire AERONET almucantar (1993–2018) and hybrid (2014–2018) scan databases by binning U27s in AOD (440 nm), Angström exponent (AE, 440–870 nm), and SSA (440, 675, 870, 1020 nm). Using this LUT approach, the uncertainty estimates U27 for each individual V3 Level 2 retrieval can be obtained by interpolation using the corresponding measured and inverted combination of AOD, AE, and SSA.

Observations of the Martian atmosphere by NOMAD on ExoMars Trace Gas Orbiter

2020 ◽  
Author(s):  
Ann Carine Vandaele ◽  
Arianna Piccialli ◽  
Ian R. Thomas ◽  
Frank Daerden ◽  
Shohei Aoki ◽  
...  
Keyword(s):  
Spectral Range ◽  
Dust Storm ◽  
Trace Gases ◽  
Martian Atmosphere ◽  
Trace Gas ◽  
Ice Clouds ◽  
Mars Atmosphere ◽  
Solar Occultation ◽  
Composition And Structure

<p>The NOMAD (“Nadir and Occultation for MArs Discovery”) spectrometer suite on board the ExoMars Trace Gas Orbiter has been designed to investigate the composition of Mars' atmosphere, with a particular focus on trace gases, clouds and dust probing the ultraviolet and infrared regions covering large parts of the 0.2-4.3 µm spectral range [1,2].</p><p>Since its arrival at Mars in April 2018, NOMAD performed solar occultation, nadir and limb observations dedicated to the determination of the composition and structure of the atmosphere. Here we report on the different discoveries highlighted by the instrument: investigation of the 2018 Global dust storm and its impact on the water uplifting and escape, its impact on temperature increases within the atmosphere as inferred by GCM modeling and observations, the dust and ice clouds distribution during the event, ozone measurements, dayglow observations and in general advances in the analysis of the spectra recorded by the three channels of NOMAD.</p><p>References</p><p>[1] Vandaele, A.C., et al., 2015. Planet. Space Sci. 119, 233-249.</p><p>[2] Vandaele et al., 2018. Space Sci. Rev., 214:80, doi.org/10.1007/s11214-11018-10517-11212.</p>

scholarly journals Airborne DOAS limb measurements of tropospheric trace gas profiles: case studies on the profile retrieval of O<sub>4</sub> and BrO

2011 ◽  
Vol 4 (6) ◽  
pp. 1241-1260 ◽  
Author(s):  
C. Prados-Roman ◽  
A. Butz ◽  
T. Deutschmann ◽  
M. Dorf ◽  
L. Kritten ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Vertical Distribution ◽  
Vertical Profile ◽  
Trace Gases ◽  
Trace Gas ◽  
Vertical Profiles ◽  
Cloud Particle ◽  
Upper Troposphere ◽  
Mixing Ratios ◽  
Tropospheric Aerosol

Abstract. A novel limb scanning mini-DOAS spectrometer for the detection of UV/vis absorbing radicals (e.g., O3, BrO, IO, HONO) was deployed on the DLR-Falcon (Deutsches Zentrum für Luft- und Raumfahrt) aircraft and tested during the ASTAR 2007 campaign (Arctic Study of Tropospheric Aerosol, Clouds and Radiation) that took place at Svalbard (78° N) in spring 2007. Our main objectives during this campaign were to test the instrument, and to perform spectral and profile retrievals of tropospheric trace gases, with particular interest on investigating the distribution of halogen compounds (e.g., BrO) during the so-called ozone depletion events (ODEs). In the present work, a new method for the retrieval of vertical profiles of tropospheric trace gases from tropospheric DOAS limb observations is presented. Major challenges arise from modeling the radiative transfer in an aerosol and cloud particle loaded atmosphere, and from overcoming the lack of a priori knowledge of the targeted trace gas vertical distribution (e.g., unknown tropospheric BrO vertical distribution). Here, those challenges are tackled by a mathematical inversion of tropospheric trace gas profiles using a regularization approach constrained by a retrieved vertical profile of the aerosols extinction coefficient EM. The validity and limitations of the algorithm are tested with in situ measured EM, and with an absorber of known vertical profile (O4). The method is then used for retrieving vertical profiles of tropospheric BrO. Results indicate that, for aircraft ascent/descent observations, the limit for the BrO detection is roughly 1.5 pptv (pmol mol−1), and the BrO profiles inferred from the boundary layer up to the upper troposphere and lower stratosphere have around 10 degrees of freedom. For the ASTAR 2007 deployments during ODEs, the retrieved BrO vertical profiles consistently indicate high BrO mixing ratios (∼15 pptv) within the boundary layer, low BrO mixing ratios (&amp;leq;1.5 pptv) in the free troposphere, occasionally enhanced BrO mixing ratios (∼1.5 pptv) in the upper troposphere, and increasing BrO mixing ratios with altitude in the lowermost stratosphere. These findings agree reasonably well with satellite and balloon-borne soundings of total and partial BrO atmospheric column densities.

scholarly journals Towards imaging of atmospheric trace gases using Fabry–Pérot interferometer correlation spectroscopy in the UV and visible spectral range

2019 ◽  
Vol 12 (1) ◽  
pp. 735-747 ◽  
Author(s):  
Jonas Kuhn ◽  
Ulrich Platt ◽  
Nicole Bobrowski ◽  
Thomas Wagner
Keyword(s):  
Temporal Resolution ◽  
Spectral Range ◽  
Trace Gases ◽  
Visible Spectral Range ◽  
Correlation Spectroscopy ◽  
Trace Gas ◽  
Atmospheric Trace Gases ◽  
Fabry Perot ◽  
Sensitivity And Selectivity ◽  
Spatio Temporal

Abstract. Many processes in the lower atmosphere including transport, turbulent mixing and chemical conversions happen on timescales of the order of seconds (e.g. at point sources). Remote sensing of atmospheric trace gases in the UV and visible spectral range (UV–Vis) commonly uses dispersive spectroscopy (e.g. differential optical absorption spectroscopy, DOAS). The recorded spectra allow for the direct identification, separation and quantification of narrow-band absorption of trace gases. However, these techniques are typically limited to a single viewing direction and limited by the light throughput of the spectrometer set-up. While two-dimensional imaging is possible by spatial scanning, the temporal resolution remains poor (often several minutes per image). Therefore, processes on timescales of seconds cannot be directly resolved by state-of-the-art dispersive methods. We investigate the application of Fabry–Pérot interferometers (FPIs) for the optical remote sensing of atmospheric trace gases in the UV–Vis spectral range. By choosing a FPI transmission spectrum, which is optimised to correlate with narrow-band (ideally periodic) absorption structures of the target trace gas, column densities of the trace gas can be determined with a sensitivity and selectivity comparable to dispersive spectroscopy, using only a small number of spectral channels (FPI tuning settings). Different from dispersive optical elements, the FPI can be implemented in full-frame imaging set-ups (cameras), which can reach high spatio-temporal resolution. In principle, FPI correlation spectroscopy can be applied for any trace gas with distinct absorption structures in the UV–Vis range. We present calculations for the application of FPI correlation spectroscopy to SO2, BrO and NO2 for exemplary measurement scenarios. In addition to high sensitivity and selectivity we find that the spatio temporal resolution of FPI correlation spectroscopy can be more than 2 orders of magnitude higher than state-of-the-art DOAS measurements. As proof of concept we built a 1-pixel prototype implementing the technique for SO2 in the UV. Good agreement with our calculations and conventional measurement techniques is demonstrated and no cross sensitivities to other trace gases are observed.

scholarly journals The governing processes and timescales of stratosphere-to-troposphere transport and its contribution to ozone in the Arctic troposphere

2009 ◽  
Vol 9 (9) ◽  
pp. 3011-3025 ◽  
Author(s):  
Q. Liang ◽  
A. R. Douglass ◽  
B. N. Duncan ◽  
R. S. Stolarski ◽  
J. C. Witte
Keyword(s):  
Lower Stratosphere ◽  
Trace Gases ◽  
Lower Troposphere ◽  
Threshold Level ◽  
The Arctic ◽  
Trace Gas ◽  
Seasonal Cycles ◽  
Upper Troposphere ◽  
Budget Analysis ◽  
Wet Removal

Abstract. We used the seasonality of a combination of atmospheric trace gases and idealized tracers to examine stratosphere-to-troposphere transport and its influence on tropospheric composition in the Arctic. Maximum stratosphere-to-troposphere transport of CFCs and O3 occurs in April as driven by the Brewer-Dobson circulation. Stratosphere-troposphere exchange (STE) occurs predominantly between 40° N to 80° N with stratospheric influx in the mid-latitudes (30–70° N) accounting for 67–81% of the air of stratospheric origin in the Northern Hemisphere extratropical troposphere. Transport from the lower stratosphere to the lower troposphere (LT) takes three months on average, one month to cross the tropopause, the second month to travel from the upper troposphere (UT) to the middle troposphere (MT), and the third month to reach the LT. During downward transport, the seasonality of a trace gas can be greatly impacted by wet removal and chemistry. A comparison of idealized tracers with varying lifetimes suggests that when initialized with the same concentrations and seasonal cycles at the tropopause, trace gases that have shorter lifetimes display lower concentrations, smaller amplitudes, and earlier seasonal maxima during transport to the LT. STE contributes to O3 in the Arctic troposphere directly from the transport of O3 and indirectly from the transport of NOy. Direct transport of O3 from the stratosphere accounts for 78% of O3 in the Arctic UT with maximum contributions occurring from March to May. The stratospheric contribution decreases significantly in the MT/LT (20–25% of total O3) and shows a very weak March–April maximum. Our NOx budget analysis in the Arctic UT shows that during spring and summer, the stratospheric injection of NOy-rich air increases NOx concentrations above the 20 pptv threshold level, thereby shifting the Arctic UT from a regime of net photochemical ozone loss to one of net production with rates as high as +16 ppbv/month.

scholarly journals Airborne limb-imaging measurements of temperature, HNO<sub>3</sub>, O<sub>3</sub>, ClONO<sub>2</sub>, H<sub>2</sub>O and CFC-12 during the Arctic winter 2015/16: characterization, in-situ validation and comparison to Aura/MLS

2018 ◽  
Author(s):  
Sören Johansson ◽  
Wolfgang Woiwode ◽  
Michael Höpfner ◽  
Felix Friedl-Vallon ◽  
Anne Kleinert ◽  
...  
Keyword(s):  
Cross Sections ◽  
Spectral Resolution ◽  
Trace Gases ◽  
High Spectral Resolution ◽  
The Arctic ◽  
Trace Gas ◽  
Atmospheric Variability ◽  
Mesoscale Structures ◽  
Research Aircraft

Abstract. The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) was operated on board the German High Altitude and LOng range (HALO) research aircraft during the PGS (POLSTRACC/GW-LCYCLE/SALSA) aircraft campaigns in the Arctic winter 2015/2016. Research flights were conducted from 17 December 2015 until 18 March 2016 between 80° W–30° E longitude and 25° N–87° N latitude. From the GLORIA infrared limb emission measurements, two dimensional cross sections of temperature, HNO3, O3, ClONO2, H2O and CFC-12 are retrieved. During 15 scientific flights of the PGS campaigns the GLORIA instrument measured more than 15 000 atmospheric profiles at high spectral resolution. Dependent on flight altitude and tropospheric cloud cover, the profiles retrieved from the measurements typically range between 5 and 14 km, and vertical resolutions between 400 m and 1000 m are achieved. The estimated total (random and systematic) 1σ errors are in the range of 1 to 2 K for temperature and 10 % to 20 % relative error for the discussed trace gases. Comparisons to in-situ instruments deployed on board HALO have been performed. Over all flights of this campaign the median differences and median absolute deviations between in-situ and GLORIA observations are −0.75 K ± 0.88 K for temperature, −0.03 ppbv ± 0.85 ppbv for HNO3, −3.5 ppbv ± 116.8 ppbv for O3, −15.4 pptv ± 102.8 pptv for ClONO2, −0.13 ppmv ± 0.63 ppmv for H2O and −19.8 pptv ± 46.9 pptv for CFC-12. These differences are mainly within the expected performances of the cross-compared instruments. Events with stronger deviations are explained by atmospheric variability and different sampling characteristics of the instruments. Additionally comparisons of GLORIA HNO3 and O3 with measurements of the Aura Microwave Limb Sounder (MLS) instrument show highly consistent structures in trace gas distributions and illustrate the potential of the high spectral resolution limb-imaging GLORIA observations for resolving narrow mesoscale structures in the UTLS.

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