This paper presents 8 years (2006–2013) of measurements obtained from Fourier transform spectrometers (FTSs) in the high Arctic at the Polar Environment Atmospheric Research Laboratory (PEARL; ...80.05° N, 86.42° W). These measurements were taken as part of the Canadian Arctic ACE (Atmospheric Chemistry Experiment) validation campaigns that have been carried out since 2004 during the polar sunrise period (from mid-February to mid-April). Each spring, two ground-based FTSs were used to measure total and partial columns of HF, O3, and trace gases that impact O3 depletion, namely, HCl and HNO3. Additionally, some tropospheric greenhouse gases and pollutant species were measured, namely CH4, N2O, CO, and C2H6. During the same time period, the satellite-based ACE-FTS made measurements near Eureka and provided profiles of the same trace gases. Comparisons have been carried out between the measurements from the Portable Atmospheric Research Interferometric Spectrometer for the InfraRed (PARIS-IR) and the co-located high-resolution Bruker 125HR FTS, as well as with the latest version of the ACE-FTS retrievals (v3.5). The total column comparison between the two co-located ground-based FTSs, PARIS-IR and Bruker 125HR, found very good agreement for most of these species (except HF), with differences well below the estimated uncertainties ( ≤ 6 %) and with high correlations (R ≥ 0. 8). Partial columns have been used for the ground-based to space-borne comparison, with coincident measurements selected based on time, distance, and scaled potential vorticity (sPV). The comparisons of the ground-based measurements with ACE-FTS show good agreement in the partial columns for most species within 6 % (except for C2H6 and PARIS-IR HF), which is consistent with the total retrieval uncertainty of the ground-based instruments. The correlation coefficients (R) of the partial column comparisons for all eight species range from approximately 0.75 to 0.95. The comparisons show no notable increases of the mean differences over these 8 years, indicating the consistency of these datasets and suggesting that the space-borne ACE-FTS measurements have been stable over this period. In addition, changes in the amounts of these trace gases during springtime between 2006 and 2013 are presented and discussed. Increased O3 (0. 9 % yr−1), HCl (1. 7 % yr−1), HF (3. 8 % yr−1), CH4 (0.5 % yr−1), and C2H6 (2. 3 % yr−1, 2009–2013) have been found with the PARIS-IR dataset, the longer of the two ground-based records.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
We present an analysis of uncertainties in global measurements of the column averaged dry-air mole fraction of CO2 (XCO2) by the NASA Orbiting Carbon Observatory-2 (OCO-2). The analysis is based on ...our best estimates for uncertainties in the OCO-2 operational algorithm and its inputs, and uses simulated spectra calculated for the actual flight and sounding geometry, with measured atmospheric analyses. The simulations are calculated for land nadir and ocean glint observations. We include errors in measurement, smoothing, interference, and forward model parameters. All types of error are combined to estimate the uncertainty in XCO2 from single soundings, before any attempt at bias correction has been made. From these results we also estimate the "variable error" which differs between soundings, to infer the error in the difference of XCO2 between any two soundings. The most important error sources are aerosol interference, spectroscopy, and instrument calibration. Aerosol is the largest source of variable error. Spectroscopy and calibration, although they are themselves fixed error sources, also produce important variable errors in XCO2. Net variable errors are usually < 1 ppm over ocean and ∼ 0.5–2.0 ppm over land. The total error due to all sources is ∼ 1.5–3.5 ppm over land and ∼ 1.5–2.5 ppm over ocean.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The Measurements of Pollution in the Troposphere (MOPITT) instrument is the only satellite-borne sensor in operation that uses both thermal (TIR) and near infrared (NIR) channels to estimate CO ...profiles. With more than fifteen years (2000 to present) of validated multi-spectral observations, this air quality and climate record provides the unique capability to separate CO in the Lower Most Troposphere (LMT, surface to 3 km (~ 700 hPa)) from the free tropospheric abundance. To extend this record, a new, hyper-spectral approach is presented here that will provide CO data products exceeding the capabilities of MOPITT instrument by combining the short wavelength infrared (SWIR, equivalent to the MOPITT NIR) channels from The TROPOspheric Monitoring Instrument (TROPOMI) aboard the European Sentinel 5 Precursor (S5p) satellite, and the TIR channels from the Cross-track Infrared Sounder (CrIS) aboard Suomi National Polar-orbiting Partnership (Suomi NPP) satellite. We apply the MUlti- SpEctra, MUlti-SpEcies, MUlti-SEnsors (MUSES) retrieval algorithm, to quantify the potential of this joint CO product. CO profiles are retrieved from a single-footprint, full spectral resolution CrIS transect over Africa on August 27--28, 2013 coincident with significant biomass burning. Comparisons of collocated CrIS and MOPITT CO observations for the LMT show a mean difference of 2.8 ± 24.9 ppb, which is well within the estimated measurement uncertainty of both sensors. The estimated degrees of freedom (DOFS) for CO signals from synergistic CrIS/TROPOMI retrievals are 0.9 in the LMT and 1.3 above LMT, which indicates that the LMT CO can be distinguished near surface CO abundance information from the free troposphere, similar to MOPITT multiple spectral observations (0.8 in the LMT, and 1.1 above LMT). In addition to increased sensitivity, the combined retrievals reduce measurement uncertainty with ~ 15 % error reduction in LMT. With a daily global coverage and a combined spatial footprint of 14 km, the joint CrIS/TROPOMI measurements have the potential to extend and improve upon the MOPITT multi-spectral CO data records for the coming decade.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
A new compact, portable Fourier transform spectrometer, called the Portable Atmospheric Research Interferometric Spectrometer for the Infrared (PARIS-IR), has been built for atmospheric remote ...sensing. The first comprehensive description of the configuration and performance of this instrument for ground-based and balloon-borne operation is provided. Sample atmospheric absorption spectra and representative results observed at the Waterloo Atmospheric Observatory (WAO) are given. The good agreement between PARIS–IR, Brewer spectrophotometer, and ozonesonde measurements of the column density of ozone at mid-latitudes demonstrate the performance and the reliability of the instrument.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Abstract
The California Laboratory for Atmospheric Remote Sensing Fourier transform spectrometer (CLARS‐FTS) deployed at Mount Wilson, California, has been measuring column abundances of greenhouse ...gases in the Los Angeles (LA) basin in the near‐infrared spectral region since August 2011. CLARS‐FTS measures reflected sunlight and has high sensitivity to absorption and scattering in the boundary layer. In this study, we estimate the retrieval biases caused by aerosol scattering and present a fast and accurate approach to correct for the bias in the CLARS column averaged CO
2
mixing ratio product,
X
CO2
. The high spectral resolution of 0.06 cm
−1
is exploited to reveal the physical mechanism for the bias. We employ a numerical radiative transfer model to simulate the impact of neglecting aerosol scattering on the CO
2
and O
2
slant column densities operationally retrieved from CLARS‐FTS measurements. These simulations show that the CLARS‐FTS operational retrieval algorithm likely underestimates CO
2
and O
2
abundances over the LA basin in scenes with moderate aerosol loading. The bias in the CO
2
and O
2
abundances due to neglecting aerosol scattering cannot be canceled by ratioing each other in the derivation of the operational product of
X
CO2
. We propose a new method for approximately correcting the aerosol‐induced bias. Results for CLARS
X
CO2
are compared to direct‐Sun
X
CO2
retrievals from a nearby Total Carbon Column Observing Network (TCCON) station. The bias‐correction approach significantly improves the correlation between the
X
CO2
retrieved from CLARS and TCCON, demonstrating that this approach can increase the yield of useful data from CLARS‐FTS in the presence of moderate aerosol loading.
Key Points
CLARS SCD retrieval shows a low bias due to aerosol scattering
Wavelength dependence of aerosol scattering causes a bias in XCO
2
XCO
2
bias can be corrected based on O
2
SCD
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The California Laboratory for Atmospheric Remote Sensing Fourier transform spectrometer (CLARS-FTS) deployed at Mount Wilson, California, has been measuring column abundances of greenhouse gases in ...the Los Angeles (LA) basin in the near-infrared spectral region since August 2011. CLARS-FTS measures reflected sunlight and has high sensitivity to absorption and scattering in the boundary layer. In this study, we estimate the retrieval biases caused by aerosol scattering and present a fast and accurate approach to correct for the bias in the CLARS column averaged CO sub(2) mixing ratio product, X sub(CO2). The high spectral resolution of 0.06cm super(-1) is exploited to reveal the physical mechanism for the bias. We employ a numerical radiative transfer model to simulate the impact of neglecting aerosol scattering on the CO sub(2) and O sub(2) slant column densities operationally retrieved from CLARS-FTS measurements. These simulations show that the CLARS-FTS operational retrieval algorithm likely underestimates CO sub(2) and O sub(2) abundances over the LA basin in scenes with moderate aerosol loading. The bias in the CO sub(2) and O sub(2) abundances due to neglecting aerosol scattering cannot be canceled by ratioing each other in the derivation of the operational product of X sub(CO2). We propose a new method for approximately correcting the aerosol-induced bias. Results for CLARS X sub(CO2) are compared to direct-Sun X sub(CO2) retrievals from a nearby Total Carbon Column Observing Network (TCCON) station. The bias-correction approach significantly improves the correlation between the X sub(CO2) retrieved from CLARS and TCCON, demonstrating that this approach can increase the yield of useful data from CLARS-FTS in the presence of moderate aerosol loading. Key Points * CLARS SCD retrieval shows a low bias due to aerosol scattering * Wavelength dependence of aerosol scattering causes a bias in XCO sub(2) * XCO sub(2) bias can be corrected based on O sub(2) SCD
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Carbonyl chlorofluoride (COClF) is an important reservoir of chlorine and fluorine in the Earth's atmosphere. Satellite-based remote sensing measurements of COClF, obtained by the Atmospheric ...Chemistry Experiment (ACE) for a time period spanning February 2004 through April 2007, have been used in a global distribution study. There is a strong source region for COClF in the tropical stratosphere near 27
km. A layer of enhanced COClF spans the low- to mid-stratosphere over all latitudes, with volume mixing ratios of 40–100 parts per trillion by volume, largest in the tropics and decreasing toward the poles. The COClF volume mixing ratio profiles are nearly zonally symmetric, but they exhibit a small hemispheric asymmetry that likely arises from a hemispheric asymmetry in the parent molecule CCl
3F. Comparisons are made with a set of in situ stratospheric measurements from the mid-1980s and with predictions from a 2-D model.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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