scholarly journals The influence of instrumental line shape degradation on NDACC gas retrievals

2018 ◽  
Author(s):  
Youwen Sun ◽  
Mathias Palm ◽  
Cheng Liu ◽  
Frank Hase ◽  
David Griffith ◽  
...  
Keyword(s):  
Line Shape ◽  
Degrees Of Freedom ◽  
Phase Error ◽  
Atmospheric Composition ◽  
Composition Change ◽  
Secondary Importance ◽  
Total Uncertainty ◽  
Instrumental Line ◽  
Different Levels ◽  
Total Column

Abstract. Instrumental line shape (ILS) degradation can cause significant biases between global FTIR (Fourier transform infrared) networks if not properly treated. Currently, how ILS degradation influences the global NDACC (Network for Detection of Atmospheric Composition Change) gases retrieval and how much ILS deviation is acceptable for each NDACC gas are still not fully quantified. We simulated ILS degradations with respect to typical types of misalignment, and compared their influence on each NDACC gas. The sensitivities of total column, root mean square of fitting residual (RMS), total random uncertainty, total systematic uncertainty, total uncertainty, degrees of freedom for signal (DOFs), and profile with respect to different levels of ILS degradation for all current NDACC gases, i.e., O3, HNO3, HCl, HF, ClONO2, CH4, CO, N2O, C2H6, and HCN, were investigated. The influence of an imperfect ILS on NDACC gases retrieval were assessed, and the consistency under different meteorological conditions and solar zenith angles (SZA) were examined. The study concluded that the influence of ILS degradation can be approximated by the linear sum of individual modulation efficiency (ME) amplitude influence and phase error (PE) influence. The PE influence is of secondary importance compared with the ME amplitude influence. For total column retrieval, the stratospheric gases are more sensitive to ILS degradation than the tropospheric gases. For profile retrieval, the positive ME has more influence on tropospheric gases than the stratospheric gases. In contrast, the negative ME has more influence on stratospheric gases than the tropospheric gases. In order to suppress the influence on total column for ClONO2 and other NDACC gases within 10 % and 1 %, respectively, the permitted maximum ILS degradation for each NDACC gas was deduced (summarized in Table 5).

scholarly journals The influence of instrumental line shape degradation on NDACC gas retrievals: total column and profile

2018 ◽  
Vol 11 (5) ◽  
pp. 2879-2896 ◽  
Author(s):  
Youwen Sun ◽  
Mathias Palm ◽  
Cheng Liu ◽  
Frank Hase ◽  
David Griffith ◽  
...  
Keyword(s):  
Line Shape ◽  
Degrees Of Freedom ◽  
Phase Error ◽  
Atmospheric Composition ◽  
Current Standard ◽  
Secondary Importance ◽  
Total Uncertainty ◽  
Instrumental Line ◽  
Ch4 And N2o ◽  
Total Column

Abstract. We simulated instrumental line shape (ILS) degradations with respect to typical types of misalignment, and compared their influence on each NDACC (Network for Detection of Atmospheric Composition Change) gas. The sensitivities of the total column, the root mean square (rms) of the fitting residual, the total random uncertainty, the total systematic uncertainty, the total uncertainty, degrees of freedom for signal (DOFs), and the profile with respect to different levels of ILS degradation for all current standard NDACC gases, i.e. O3, HNO3, HCl, HF, ClONO2, CH4, CO, N2O, C2H6, and HCN, were investigated. The influence of an imperfect ILS on NDACC gases' retrieval was assessed, and the consistency under different meteorological conditions and solar zenith angles (SZAs) were examined. The study concluded that the influence of ILS degradation can be approximated by the linear sum of individual modulation efficiency (ME) amplitude influence and phase error (PE) influence. The PE influence is of secondary importance compared with the ME amplitude. Generally, the stratospheric gases are more sensitive to ILS degradation than the tropospheric gases, and the positive ME influence is larger than the negative ME. For a typical ILS degradation (10 %), the total columns of stratospheric gases O3, HNO3, HCl, HF, and ClONO2 changed by 1.9, 0.7, 4, 3, and 23 %, respectively, while the columns of tropospheric gases CH4, CO, N2O, C2H6, and HCN changed by 0.04, 2.1, 0.2, 1.1, and 0.75 %, respectively. In order to suppress the fractional difference in the total column for ClONO2 and other NDACC gases within 10 and 1 %, respectively, the maximum positive ME degradations for O3, HNO3, HCl, HF, ClONO2, CO, C2H6, and HCN should be less than 6, 15, 5, 5, 5, 5, 9, and 13 %, respectively; the maximum negative ME degradations for O3, HCl, and HF should be less than 6, 12, and 12 %, respectively; the influence of ILS degradation on CH4 and N2O can be regarded as being negligible.

scholarly journals Improved instrumental line shape monitoring for the ground-based, high-resolution FTIR spectrometers of the Network for the Detection of Atmospheric Composition Change

2012 ◽  
Vol 5 (3) ◽  
pp. 603-610 ◽  
Author(s):  
F. Hase
Keyword(s):  
High Resolution ◽  
Line Shape ◽  
Path Length ◽  
Pressure Gauge ◽  
Atmospheric Composition ◽  
Composition Change ◽  
Chemical Monitoring ◽  
Instrumental Line ◽  
Long Timescales ◽  
Single Calibration

Abstract. We propose an improved monitoring scheme for the instrumental line shape (ILS) of high-resolution, ground-based FTIR (Fourier Transform InfraRed) spectrometers used for chemical monitoring of the atmosphere by the Network for Detection of Atmospheric Composition Change (NDACC). Good ILS knowledge is required for the analysis of the recorded mid-infrared spectra. The new method applies a sequence of measurements using different gas cells instead of a single calibration cell. Three cells are used: cell C1 is a refillable cell offering 200 mm path length and equipped with a pressure gauge (filled with 100 Pa N2O), cells C2 and C3 are sealed cells offering 75 mm path length. C2 is filled with 5 Pa of pure N2O. Cell C3 is filled with 16 Pa N2O in 200 hPa technical air, so provides pressure-broadened N2O lines. We demonstrate that an ILS retrieval using C1 improves significantly the sensitivity of the ILS retrieval over the current calibration cells used in the network, because this cell provides narrow fully saturated N2O lines. The N2O columns derived from C2 and C3 allow the performance of a highly valuable closure experiment: adopting the ILS retrieved from C1, the N2O columns of C2 and C3 are derived. Because N2O is an inert gas, both columns should be constant on long timescales. Apparent changes in the columns would immediately attract attention and indicate either inconsistent ILS results or instrumental problems of other origin. Two different cells are applied for the closure experiment, because the NDACC spectrometers observe both stratospheric and tropospheric gases: C2 mimics signatures of stratospheric gases, whereas C3 mimics signatures of tropospheric gases.

scholarly journals Technical note: Sensitivity of instrumental line shape monitoring for the ground-based high-resolution FTIR spectrometer with respect to different optical attenuators

2017 ◽  
Vol 10 (3) ◽  
pp. 989-997 ◽  
Author(s):  
Youwen Sun ◽  
Mathias Palm ◽  
Christine Weinzierl ◽  
Christof Petri ◽  
Justus Notholt ◽  
...  
Keyword(s):  
High Resolution ◽  
Line Shape ◽  
Radiant Energy ◽  
Technical Note ◽  
Total Carbon ◽  
Atmospheric Composition ◽  
Incident Intensity ◽  
Instrumental Line ◽  
Ftir Spectrometer ◽  
Potential Strategy

Abstract. The TCCON (Total Carbon Column Observing Network) and most NDACC (Network for Detection of Atmospheric Composition Change) sites assume an ideal ILS (instrumental line shape) for analysis of the spectra. In order to adapt the radiant energy received by the detector, an attenuator or different sizes of field stop can be inserted in the light path. These processes may alter the alignment of a high-resolution FTIR (Fourier transform infrared) spectrometer, and may result in bias due to ILS drift. In this paper, we first investigated the sensitivity of the ILS monitoring with respect to application of different kinds of attenuators for ground-based high-resolution FTIR spectrometers within the TCCON and NDACC networks. Both lamp and sun cell measurements were conducted after the insertion of five different attenuators in front of and behind the interferometer. The ILS characteristics derived from lamp and sun spectra are in good agreement. ILSs deduced from all lamp cell measurements were compared. As a result, the disturbances to the ILS of a high-resolution FTIR spectrometer with respect to the insertion of different attenuators at different positions were quantified. A potential strategy to adapt the incident intensity of a detector was finally deduced.

scholarly journals Construction of merged satellite total O<sub>3</sub> and NO<sub>2</sub> time series in the tropics for trend studies and evaluation by comparison to NDACC SAOZ measurements

2014 ◽  
Vol 7 (10) ◽  
pp. 3337-3354 ◽  
Author(s):  
M. Pastel ◽  
J.-P. Pommereau ◽  
F. Goutail ◽  
A. Richter ◽  
A. Pazmiño ◽  
...  
Keyword(s):  
Time Series ◽  
Lower Stratosphere ◽  
Atmospheric Composition ◽  
Data Sets ◽  
Composition Change ◽  
Long Time ◽  
Uv Visible ◽  
The Tropics ◽  
Lower Noise ◽  
Total Column

Abstract. Long time series of ozone and NO2 total column measurements in the southern tropics are available from two ground-based SAOZ (Système d'Analyse par Observation Zénithale) UV-visible spectrometers operated within the Network for the Detection of Atmospheric Composition Change (NDACC) in Bauru (22° S, 49° W) in S-E Brazil since 1995 and Reunion Island (21° S, 55° E) in the S-W Indian Ocean since 1993. Although the stations are located at the same latitude, significant differences are observed in the columns of both species, attributed to differences in tropospheric content and equivalent latitude in the lower stratosphere. These data are used to identify which satellites operating during the same period, are capturing the same features and are thus best suited for building reliable merged time series for trend studies. For ozone, the satellites series best matching SAOZ observations are EP-TOMS (1995–2004) and OMI-TOMS (2005–2011), whereas for NO2, best results are obtained by combining GOME version GDP5 (1996–2003) and SCIAMACHY – IUP (2003–2011), displaying lower noise and seasonality in reference to SAOZ. Both merged data sets are fully consistent with the larger columns of the two species above South America and the seasonality of the differences between the two stations, reported by SAOZ, providing reliable time series for further trend analyses and identification of sources of interannual variability in the future analysis.

scholarly journals Retrieval of xCO<sub>2</sub> from ground-based mid-infrared (NDACC) solar absorption spectra and comparison to TCCON

2016 ◽  
Vol 9 (2) ◽  
pp. 577-585 ◽  
Author(s):  
Matthias Buschmann ◽  
Nicholas M. Deutscher ◽  
Vanessa Sherlock ◽  
Mathias Palm ◽  
Thorsten Warneke ◽  
...  
Keyword(s):  
Absorption Spectra ◽  
Seasonal Cycle ◽  
Total Carbon ◽  
Atmospheric Composition ◽  
Composition Change ◽  
Solar Absorption ◽  
Mid Infrared ◽  
Infrared Spectral ◽  
Ftir Spectrometer ◽  
Total Column

Abstract. High-resolution solar absorption spectra, taken within the Network for the Detection of Atmospheric Composition Change Infrared Working Group (NDACC-IRWG) in the mid-infrared spectral region, are used to infer partial or total column abundances of many gases. In this paper we present the retrieval of a column-averaged mole fraction of carbon dioxide from NDACC-IRWG spectra taken with a Fourier transform infrared (FTIR) spectrometer at the site in Ny-Ålesund, Spitsbergen. The retrieved time series is compared to colocated standard TCCON (Total Carbon Column Observing Network) measurements of column-averaged dry-air mole fractions of CO2 (denoted by xCO2). Comparing the NDACC and TCCON retrievals, we find that the sensitivity of the NDACC retrieval is lower in the troposphere (by a factor of 2) and higher in the stratosphere, compared to TCCON. Thus, the NDACC retrieval is less sensitive to tropospheric changes (e.g., the seasonal cycle) in the column average.

scholarly journals Comparison of ground-based FTIR and Brewer O<sub>3</sub> total column with data from two different IASI algorithms and from OMI and GOME-2 satellite instruments

2011 ◽  
Vol 4 (3) ◽  
pp. 535-546 ◽  
Author(s):  
C. Viatte ◽  
M. Schneider ◽  
A. Redondas ◽  
F. Hase ◽  
M. Eremenko ◽  
...  
Keyword(s):  
Atmospheric Composition ◽  
Composition Change ◽  
Neural Network Analysis ◽  
Ozone Monitoring Instrument ◽  
Atmospheric Sounding ◽  
Infrared Spectrometer ◽  
Operational Algorithm ◽  
Ozone Monitoring ◽  
Total Column ◽  
Observing Systems

Abstract. An intercomparison of ozone total column measurements derived from various platforms is presented in this work. Satellite data from Infrared Atmospheric Sounding Interferometer (IASI), Ozone Monitoring Instrument (OMI) and Global Ozone Monitoring Experiment (GOME-2) are compared with data from two ground-based spectrometers (Fourier Transform Infrared spectrometer FTIR and Brewer), located at the Network for Detection of Atmospheric Composition Change (NDACC) super-site of Izaña (Tenerife), measured during a campaign from March to June 2009. These ground-based observing systems have already been demonstrated to perform consistent, precise and accurate ozone total column measurements. An excellent agreement between ground-based and OMI/GOME-2 data is observed. Results from two different algorithms for deriving IASI ozone total column are also compared: the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT/ESA) operational algorithm and the LISA (Laboratoire Inter-universitaire des Systèmes Atmosphériques) algorithm. A better agreement was found with LISA's analytical approach based on an altitude-dependent Tikhonov-Philips regularization: correlations are 0.94 and 0.89 compared to FTIR and Brewer, respectively; while the operational IASI ozone columns (based on neural network analysis) show correlations of 0.90 and 0.85, respectively, compared to the O3 columns obtained from FTIR and Brewer.

scholarly journals Comparison of ground-based FTIR and Brewer O<sub>3</sub> total column with data from two different IASI algorithms and from OMI and GOME-2 satellite instruments

2010 ◽  
Vol 3 (6) ◽  
pp. 5833-5865
Author(s):  
C. Viatte ◽  
M. Schneider ◽  
A. Redondas ◽  
F. Hase ◽  
M. Eremenko ◽  
...  
Keyword(s):  
Atmospheric Composition ◽  
Composition Change ◽  
Neural Network Analysis ◽  
Ozone Monitoring Instrument ◽  
Atmospheric Sounding ◽  
Infrared Spectrometer ◽  
Operational Algorithm ◽  
Ozone Monitoring ◽  
Total Column ◽  
Observing Systems

Abstract. An intercomparison of ozone total column measurements derived from various platforms is presented in this work. Satellite data from Infrared Atmospheric Sounding Interferometer (IASI), Ozone Monitoring Instrument (OMI) and Global Ozone Monitoring Experiment (GOME-2) are compared with data from two ground-based spectrometers (Fourier Transform Infrared spectrometer FTIR and Brewer), located at the Network for Detection of Atmospheric Composition Change (NDACC) super-site of Izaña (Tenerife), measured during a campaign from March to June 2009. These ground-based observing systems have already been demonstrated to perform consistent, precise and accurate ozone total column measurements. An excellent agreement between ground-based and OMI/GOME-2 data is observed. Results from two different algorithms for deriving IASI ozone total column are also compared: the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT/ESA) operational algorithm and the LISA (Laboratoire Interuniversitaire des Systèmes Atmosphériques) algorithm. A better agreement was found with LISA's analytical approach based on an altitude-dependent Tikhonov-Philips regularization: correlations are 0.94 and 0.89 compared to FTIR and Brewer, respectively; while the operational IASI ozone columns (based on neural network analysis) show correlations of 0.90 and 0.85, respectively, compared to the O3 columns obtained from FTIR and Brewer.

scholarly journals Validation of the CrIS fast physical NH<sub>3</sub> retrieval with ground-based FTIR

2017 ◽  
Vol 10 (7) ◽  
pp. 2645-2667 ◽  
Author(s):  
Enrico Dammers ◽  
Mark W. Shephard ◽  
Mathias Palm ◽  
Karen Cady-Pereira ◽  
Shannon Capps ◽  
...  
Keyword(s):  
Relative Difference ◽  
Atmospheric Composition ◽  
Absolute Difference ◽  
Lower Sensitivity ◽  
Composition Change ◽  
Atmospheric Concentration ◽  
The Absolute ◽  
Cross Track ◽  
Median Absolute Difference ◽  
Total Column

Abstract. Presented here is the validation of the CrIS (Cross-track Infrared Sounder) fast physical NH3 retrieval (CFPR) column and profile measurements using ground-based Fourier transform infrared (FTIR) observations. We use the total columns and profiles from seven FTIR sites in the Network for the Detection of Atmospheric Composition Change (NDACC) to validate the satellite data products. The overall FTIR and CrIS total columns have a positive correlation of r  =  0.77 (N  =  218) with very little bias (a slope of 1.02). Binning the comparisons by total column amounts, for concentrations larger than 1.0  ×  1016 molecules cm−2, i.e. ranging from moderate to polluted conditions, the relative difference is on average ∼ 0–5 % with a standard deviation of 25–50 %, which is comparable to the estimated retrieval uncertainties in both CrIS and the FTIR. For the smallest total column range (< 1.0  × 1016 molecules cm−2) where there are a large number of observations at or near the CrIS noise level (detection limit) the absolute differences between CrIS and the FTIR total columns show a slight positive column bias. The CrIS and FTIR profile comparison differences are mostly within the range of the single-level retrieved profile values from estimated retrieval uncertainties, showing average differences in the range of  ∼ 20 to 40 %. The CrIS retrievals typically show good vertical sensitivity down into the boundary layer which typically peaks at  ∼ 850 hPa (∼ 1.5 km). At this level the median absolute difference is 0.87 (std  =  ±0.08) ppb, corresponding to a median relative difference of 39 % (std  =  ±2 %). Most of the absolute and relative profile comparison differences are in the range of the estimated retrieval uncertainties. At the surface, where CrIS typically has lower sensitivity, it tends to overestimate in low-concentration conditions and underestimate in higher atmospheric concentration conditions.

scholarly journals Intercomparison and evaluation of ground- and satellite-based stratospheric ozone and temperature profiles above Observatoire de Haute-Provence during the Lidar Validation NDACC Experiment (LAVANDE)

2020 ◽  
Vol 13 (10) ◽  
pp. 5621-5642
Author(s):  
Robin Wing ◽  
Wolfgang Steinbrecht ◽  
Sophie Godin-Beekmann ◽  
Thomas J. McGee ◽  
John T. Sullivan ◽  
...  
Keyword(s):  
Stratospheric Ozone ◽  
The Other ◽  
Atmospheric Composition ◽  
Temperature Profiles ◽  
Composition Change ◽  
Total Uncertainty ◽  
Broadband Emission ◽  
Uncertainty Estimates ◽  
532 Nm ◽  
Good Agreement

Abstract. A two-part intercomparison campaign was conducted at Observatoire de Haute-Provence (OHP) for the validation of lidar ozone and temperature profiles using the mobile NASA Stratospheric Ozone Lidar (NASA STROZ), satellite overpasses from the Microwave Limb Sounder (MLS), the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER), meteorological radiosondes launched from Nîmes, and locally launched ozonesondes. All the data were submitted and compared “blind”, before the group could see results from the other instruments. There was good agreement between all ozone measurements between 20 and 40 km, with differences of generally less than 5 % throughout this region. Below 20 km, SABER and MLS measured significantly more ozone than the lidars or ozonesondes. Temperatures for all lidars were in good agreement between 30 and 60 km, with differences on the order of ±1 to 3 K. Below 30 km, the OHP lidar operating at 532 nm has a significant cool bias due to contamination by aerosols. Systematic, altitude-varying bias up to ±5 K compared to the lidars was found for MLS at many altitudes. SABER temperature profiles are generally closer to the lidar profiles, with up 3 K negative bias near 50 km. Total uncertainty estimates for ozone and temperature appear to be realistic for nearly all systems. However, it does seem that the very low estimated uncertainties of lidars between 30 and 50 km, between 0.1 and 1 K, are not achieved during Lidar Validation Network for the Detection of Atmospheric Composition Change (NDACC) Experiment (LAVANDE). These estimates might have to be increased to 1 to 2 K.

scholarly journals Calibration of sealed HCl cells used for TCCON instrumental line shape monitoring

2013 ◽  
Vol 6 (12) ◽  
pp. 3527-3537 ◽  
Author(s):  
F. Hase ◽  
B. J. Drouin ◽  
C. M. Roehl ◽  
G. C. Toon ◽  
P. O. Wennberg ◽  
...  
Keyword(s):  
Line Shape ◽  
Individual Cell ◽  
Calibration Procedure ◽  
Total Carbon ◽  
Effective Pressure ◽  
Error Source ◽  
Secondary Importance ◽  
Instrumental Line ◽  
Network Consistency ◽  
Shape Monitoring

Abstract. The TCCON (Total Carbon Column Observing Network) FTIR (Fourier transform infrared) network provides highly accurate observations of greenhouse gas column-averaged dry-air mole fractions. As an important component of TCCON quality assurance, sealed cells filled with approximately 5 mbar of HCl are used for instrumental line shape (ILS) monitoring at all TCCON sites. Here, we introduce a calibration procedure for the HCl cells which employs a refillable, pressure-monitored reference cell filled with C2H2. Using this method, we identify variations of HCl purity between the TCCON cells as a non-negligible disturbance. The new calibration procedure introduced here assigns effective pressure values to each individual cell to account for additional broadening of the HCl lines. This approach will improve the consistency of the network by significantly reducing possible station-to-station biases due to inconsistent ILS results from different HCl cells. We demonstrate that the proposed method is accurate enough to turn the ILS uncertainty into an error source of secondary importance from the viewpoint of network consistency.

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