scholarly journals Retrieval of Ozone Total Columns over Evora-Portugal Using Remote Sensing Instruments During 2007-2011

2015 ◽  
Vol XL-7/W3 ◽  
pp. 173-177
Author(s):  
A. F. Domingues ◽  
D. Bortoli ◽  
A. M. Silva ◽  
P. Kulkarni ◽  
R. Mendes
Keyword(s):  
Seasonal Cycle ◽  
Trace Gases ◽  
Optical Absorption Spectroscopy ◽  
Vertical Profiles ◽  
Middle Latitudes ◽  
Ozone Monitoring ◽  
Scanning Imaging ◽  
Atmospheric Tracers ◽  
Total Column ◽  
Good Agreement

The present study deals with the retrieval of Ozone (O3) Total Column (TOC) and analysis of its variability over the Observatory of the Geophysics Centre of Évora (CGE-UE) –Portugal (38.5ºN; 7.9 ºW, 300 m a.s.l.) for the period comprised 2007-2011. The data presented in this study are obtained applying the Differential Optical Absorption Spectroscopy (DOAS) methodology to the measurements of diffused spectral sky radiation carried out along the zenith direction performed with the multipurpose UV-Vis. Spectrometer for Atmospheric Tracers Monitoring (SPATRAM) in the 250-900 nm spectral range. This ground-based spectrometer is installed at CGE-UE performing daily and automatic measurements since 2004. Other products of this scanning spectrometer are the vertical profiles of some trace gases (e.g. NO2) and monitoring of air quality. The O3 retrieved with the SPATRAM instrument confirm the typical seasonal cycle for middle latitudes reaching the maximum during the spring and the minimum during the autumn. The ground-based results obtained for O3 column are also compared with data from SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) and Global Ozone Monitoring Experiment (GOME) instruments aboard ENVISAT and ERS-2 satellites, respectively. The results show a good agreement between the datasets. The main reasons for the observed differences are discussed.

scholarly journals Vertical profiles of NO<sub>2</sub>, SO<sub>2</sub>, HONO, HCHO, CHOCHO, and aerosols derived from MAX-DOAS measurements at a rural site in the central-western North China Plain and their relation to emission sources and effects of regional transport

2018 ◽  
Author(s):  
Yang Wang ◽  
Steffen Dörner ◽  
Sebastian Donner ◽  
Sebastian Böhnke ◽  
Isabelle De Smedt ◽  
...  
Keyword(s):  
Trace Gases ◽  
Rural Site ◽  
Optical Absorption Spectroscopy ◽  
Vertical Profiles ◽  
Regional Transport ◽  
Near Surface ◽  
North West ◽  
Mixing Ratios ◽  
Chemistry Research

Abstract. A Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) instrument was deployed in May and June 2016 at a monitoring station (37.18° N, 114.36° E) in the suburban area of Xingtai (one of the most polluted cities in China) during the Atmosphere-Aerosol-Boundary Layer-Cloud (A2BC) and Air chemistry Research In Asia (ARIAs) joint experiments to derive tropospheric vertical profiles of NO2, SO2, HONO, HCHO, CHOCHO and aerosols. Aerosol optical depths derived from MAX-DOAS were found to be consistent with collocated sun-photometer measurements. Also the derived near-surface aerosol extinction and HCHO mixing ratio agree well with coincident visibility meter and in situ HCHO measurements, with mean HCHO near-surface mixing ratios of ~ 3.5 ppb. Underestimates of MAX-DOAS results compared to in situ measurements of NO2 (~ 60 %), SO2 (~ 20 %) are found expectedly due to vertical and horizontal inhomogeneity of trace gases. Vertical profiles of aerosols and NO2, SO2 are reasonably consistent with those measured by a collocated Raman Lidar and aircraft spirals over the station. The deviations can be attributed to differences in sensitivity as a function of altitude and substantial horizontal gradients of pollutants. Aerosols, HCHO, and CHOCHO profiles typically extended to higher altitudes (with 75 % integrated column located below ~ 1.4 km) than did NO2, SO2, and HONO (with 75 % integrated column below ~ 0.5 km) under polluted condition. Lifted layers were systematically observed for all species, (except HONO), indicating accumulation, secondary formation, or long-range transport of the pollutants at higher altitudes. Maximum values routinely occurred in the morning for NO2, SO2, and HONO, but around noon for aerosols, HCHO, and CHOCHO, mainly dominated by photochemistry, characteristic upslope/downslope circulation and PBL dynamics. Significant day-to-day variations are found for all species due to the effect of regional transport and changes in synoptic pattern analysed with HYSPLIT trajectories. Low pollution was often observed for air masses from the north-west (behind cold fronts), and high pollution from the southern areas such as industrialized Wuan. The contribution of regional transport for the pollutants measured at the site during the observation period was estimated to be about 20 % to 30 % for trace gases, and about 50 % for aerosols. In addition, agricultural burning events impacted the day-to-day variations of HCHO, CHOCHO and aerosols.

scholarly journals Cloud detection and classification based on MAX-DOAS observations

2013 ◽  
Vol 6 (6) ◽  
pp. 10297-10360 ◽  
Author(s):  
T. Wagner ◽  
S. Beirle ◽  
S. Dörner ◽  
U. Friess ◽  
J. Remmers ◽  
...  
Keyword(s):  
Classification Scheme ◽  
Scattered Light ◽  
Trace Gases ◽  
Colour Index ◽  
Optical Absorption Spectroscopy ◽  
Cloud Detection ◽  
Clear Sky ◽  
Cloud Classification ◽  
Good Agreement ◽  
Light Ring

Abstract. Multi-AXis-Differential Optical Absorption Spectroscopy (MAX-DOAS) observations of aerosols and trace gases can be strongly influenced by clouds. Thus it is important to identify clouds and characterise their properties. In this study we investigate the effects of clouds on several quantities which can be derived from MAX-DOAS observations, like the radiance, the colour index (radiance ratio at two selected wavelengths), the absorption of the oxygen dimer O4 and the fraction of inelastically scattered light (Ring effect). To identify clouds, these quantities can be either compared to their corresponding clear sky reference values, or their dependencies on time or viewing direction can be analysed. From the investigation of the temporal variability the influence of clouds can be identified even for individual measurements. Based on our investigations we developed a cloud classification scheme, which can be applied in a flexible way to MAX-DOAS or zenith DOAS observations: in its simplest version, zenith observations of the colour index are used to identify the presence of clouds (or high aerosol load). In more sophisticated versions, also other quantities and viewing directions are considered, which allows sub-classifications like e.g. thin or thick clouds, or fog. We applied our cloud classification scheme to MAX-DOAS observations during the CINDI campaign in the Netherlands in Summer 2009 and found very good agreement with sky images taken from ground.

scholarly journals Tropospheric CO vertical profiles deduced from total columns using data assimilation: methodology and validation

2013 ◽  
Vol 6 (4) ◽  
pp. 6517-6566 ◽  
Author(s):  
L. El Amraoui ◽  
J.-L. Attié ◽  
P. Ricaud ◽  
W. A. Lahoz ◽  
A. Piacentini ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Chemical Species ◽  
Attractive Alternative ◽  
Observation Error ◽  
Vertical Profiles ◽  
The Mean ◽  
Using Data ◽  
Total Column ◽  
Co Concentrations ◽  
Good Agreement

Abstract. This paper presents a validation of a method to derive the vertical profile of carbon monoxide (CO) from its total column using data assimilation. The main motivation of this study is twofold. First, to deduce both the vertical CO profiles and the assimilated CO fields with good confidence. Second, for chemical species that can be measured only as the total column, this method provides an attractive alternative for estimating their vertical profiles in the troposphere. We choose version 3 (V3) of MOPITT CO total columns to validate the proposed method. MOPITT has the advantage of providing both the vertical profiles and the total columns of CO. Furthermore, this version has been extensively validated by comparison with many independent datasets, and has been used in many scientific studies. The first step of the paper consists in the specification of the observation errors based on the Chi-square (χ2) test. The observations have been binned according to day, night, land and sea (LAND_DAY, LAND_NIGHT and SEA, respectively). The respective optimal observation error values for which the χ2 metric is the closest to 1 are: 7%, 8% and 11% for SEA, LAND_DAY and LAND_NIGHT, respectively. In a second step, the CO total column, with its specified errors, is used within the assimilation system to estimate the vertical profiles. These are validated by comparison with vertical profiles of MOPITT V3 retrievals at global and regional scales. Generally, both datasets show similar patterns and good agreement at both global and regional scales. Nevertheless, the total column analyses (TOTCOL_ANALYSES) slightly overestimate CO concentrations compared to MOPITT observations. In a third step, vertical profiles calculated from TOTCOL_ANALYSES have been compared to those calculated from the assimilation of MOPITT V3 vertical profiles (PROFILE_ANALYSES). Both datasets shows very good agreement, but TOTCOL_ANALYSES tend to slightly overestimate CO concentrations. The mean bias between both datasets is 6% and 8% at the pressure levels 700 and 200 hPa, respectively. In terms of zonal means, the CO distribution is similar for both analyses. The mean bias between these datasets is low and doesn't exceed 12%. These results confirm that both analyses (total column and vertical profiles) are in very good agreement at global and regional scales.

scholarly journals Stratospheric CH<sub>4</sub> and CO<sub>2</sub> profiles derived from SCIAMACHY solar occultation measurements

2015 ◽  
Vol 8 (11) ◽  
pp. 11467-11511 ◽  
Author(s):  
S. Noël ◽  
K. Bramstedt ◽  
M. Hilker ◽  
P. Liebing ◽  
J. Plieninger ◽  
...  
Keyword(s):  
Time Series ◽  
Weighting Function ◽  
Optical Absorption Spectroscopy ◽  
Data Sets ◽  
Solar Occultation ◽  
Scanning Imaging ◽  
Carbon Dioxide Co2 ◽  
Latitudinal Range ◽  
Total Column

Abstract. Stratospheric profiles of methane (CH4) and carbon dioxide (CO2) have been derived from solar occultation measurements of the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY). The retrieval is performed using a method called "Onion Peeling DOAS" (ONPD) which combines an onion peeling approach with a weighting function DOAS (Differential Optical Absorption Spectroscopy) fit. By use of updated pointing information and optimisation of the data selection and of the retrieval approach the altitude range for reasonable CH4 could be extended to about 17 to 45 km. Furthermore, the quality of the derived CO2 has been assessed such that now the first stratospheric profiles of CO2 from SCIAMACHY are available. Comparisons with independent data sets yield an estimated accuracy of the new SCIAMACHY stratospheric profiles of about 5–10 % for CH4 and 2–3 % for CO2. The accuracy of the products is currently mainly restricted by the appearance of unexpected vertical oscillations in the derived profiles which need further investigation. Using the improved ONPD retrieval, CH4 and CO2 stratospheric data sets covering the whole SCIAMACHY time series (August 2002–April 2012) and the latitudinal range between about 50 and 70° N have been derived. Based on these time series, CH4 and CO2 trends have been estimated, which are in reasonable agreement with total column trends for these gases. This shows that the new SCIAMACHY data sets can provide valuable information about the stratosphere.

scholarly journals Long-term tropospheric formaldehyde concentrations deduced from ground-based fourier transform solar infrared measurements

2007 ◽  
Vol 7 (5) ◽  
pp. 14543-14568 ◽  
Author(s):  
N. B. Jones ◽  
K. Riedel ◽  
W. Allan ◽  
S. Wood ◽  
P. I. Palmer ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Seasonal Cycle ◽  
Fourier Transform Spectrometer ◽  
The Sun ◽  
Ch4 Oxidation ◽  
Infrared Measurements ◽  
Ozone Monitoring ◽  
Total Column ◽  
Standard Techniques

Abstract. Long-term total column measurements of formaldehyde (HCHO) covering a 12 year period from 1992 to 2004 are reported from spectra recorded with a high-resolution Fourier Transform Spectrometer (FTS) using the sun as a light source at a Southern Hemisphere site (Lauder, New Zealand). The ambient HCHO concentrations at this rural location are often at background levels (<250 ppt) typical for remote marine environments. Due to these low values of HCHO, which are often at or below the detection limit of standard techniques, a method of analysis has been developed that successfully produces HCHO columns with sufficient sensitivity throughout the whole season. The HCHO column over Lauder was found to have a strong seasonal cycle (±50%), with a mean column of 4.2×1015 molecules cm−2, the maximum occurring in the summer. A simple box model of CH4 oxidation reproduces the seasonal cycle, but significantly underestimates the maximum HCHO ground concentrations deduced from the column observations, particularly in summer. This implies the existence of a significant source of HCHO that cannot be explained by oxidation of CH4 alone. The ground-based FTS column data compares well with collocated HCHO column measurements from the Global Ozone Monitoring Experiment (GOME) satellite instrument (r2=0.65, mean bias=10%, n=48).

scholarly journals Averaging kernels for DOAS total-column satellite retrievals

2003 ◽  
Vol 3 (1) ◽  
pp. 895-910
Author(s):  
H. J. Eskes ◽  
K. F. Boersma
Keyword(s):  
Optical Absorption ◽  
Trace Gases ◽  
A Priori ◽  
Systematic Errors ◽  
Optical Absorption Spectroscopy ◽  
Additional Information ◽  
Satellite Validation ◽  
Satellite Retrievals ◽  
Uv Visible ◽  
Total Column

Abstract. The Differential Optical Absorption Spectroscopy (DOAS) method is used extensively to retrieve total column amounts of trace gases based on UV-visible measurements of satellite spectrometers, such as ERS-2 GOME. In practice the sensitivity of the instrument to the tracer density is strongly height dependent, especially in the troposphere. The resulting tracer profile dependence may introduce large systematic errors in the retrieved columns that are difficult to quantify without proper additional information, as provided by the averaging kernel (AK). In this paper we generalise the AK concept to total column retrievals, and derive an explicit expression for the DOAS AK. It is shown that the additional AK information corrects for the a priori dependence of the retrieval. The availability of averaging kernel information as part of the total column retrieval product is essential for the interpretation of the observations, and for applications like chemical data assimilation and detailed satellite validation studies.

scholarly journals Intercomparison of stratospheric nitrogen dioxide columns retrieved from ground-based DOAS and FTIR and satellite DOAS instruments over the subtropical Izana station

2016 ◽  
Vol 9 (9) ◽  
pp. 4471-4485 ◽  
Author(s):  
Cristina Robles-Gonzalez ◽  
Mónica Navarro-Comas ◽  
Olga Puentedura ◽  
Matthias Schneider ◽  
Frank Hase ◽  
...  
Keyword(s):  
Relative Difference ◽  
Field Of View ◽  
Atmospheric Composition ◽  
Optical Absorption Spectroscopy ◽  
Data Series ◽  
Composition Change ◽  
Ozone Monitoring Instrument ◽  
Vertical Column ◽  
Ozone Monitoring ◽  
Scanning Imaging

Abstract. A 13-year analysis (2000–2012) of the NO2 vertical column densities derived from ground-based (GB) instruments and satellites has been carried out over the Izaña NDACC (Network for the Detection of the Atmospheric Composition Change) subtropical site. Ground-based DOAS (differential optical absorption spectroscopy) and FTIR (Fourier transform infrared spectroscopy) instruments are intercompared to test mutual consistency and then used for validation of stratospheric NO2 from OMI (Ozone Monitoring Instrument) and SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY). The intercomparison has been carried out taking into account the various differences existing in instruments, namely temporal coincidence, collocation, sensitivity, field of view, etc. The paper highlights the importance of considering an “effective solar zenith angle” instead of the actual one when comparing direct-sun instruments with zenith sky ones for a proper photochemical correction. Results show that NO2 vertical column densities mean relative difference between FTIR and DOAS instruments is 2.8 ± 10.7 % for a.m. data. Both instruments properly reproduce the NO2 seasonal and the interannual variation. Mean relative difference of the stratospheric NO2 derived from OMI and DOAS is −0.2 ± 8.7 % and from OMI and FTIR is −1.6 ± 6.7 %. SCIAMACHY mean relative difference is of 3.7 ± 11.7 and −5.7 ± 11.0 % for DOAS and FTIR, respectively. Note that the days used for the intercomparison are not the same for all the pairs of instruments since it depends on the availability of data. The discrepancies are found to be seasonally dependent with largest differences in winter and excellent agreement in the spring months (AMJ). A preliminary analysis of NO2 trends has been carried out with the available data series. Results show increases in stratospheric NO2 columns in all instruments but larger values in those that are GB than that expected by nitrous oxide oxidation. The possible reasons for the discrepancy between instruments and the positive trends are discussed in the text.

scholarly journals Intercomparison exercise between different radiative transfer models used for the interpretation of ground-based zenith-sky and multi-axis DOAS observations

2005 ◽  
Vol 5 (5) ◽  
pp. 7929-7964
Author(s):  
F. Hendrick ◽  
M. Van Roozendael ◽  
A. Kylling ◽  
A. Petritoli ◽  
A. Rozanov ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Trace Gases ◽  
Relative Difference ◽  
Optical Absorption Spectroscopy ◽  
Vertical Column ◽  
Intercomparison Exercise ◽  
Aerosol Effect ◽  
Aerosol Scattering ◽  
Funded Project ◽  
Good Agreement

Abstract. We present the results of an intercomparison exercise between six different radiative transfer (RT) models carried out in the framework of QUILT, an EU funded project based on the exploitation of the Network for the Detection of Stratospheric Change (NDSC). RT modeling is an important step in the interpretation of Differential Optical Absorption Spectroscopy (DOAS) observations. It allows the conversion of the slant column densities (SCDs) into vertical column densities (VCDs) using calculated air mass factors (AMFs). The originality of our study resides in comparing SCD simulations in multi-axis (MAX) geometry (trace gases: NO2 and HCHO) and in taking into account the photochemical enhancement for calculating SCDs of rapidly photolysing species (BrO, NO2, and OClO) in zenith-sky geometry. Concerning the MAX simulations, good agreement is observed between the different models with the calculated NO2 and HCHO SCDs differing by no more than 5% in the elevation and solar zenith angles (SZA) ranges investigated (5°–20° and 35°–85°, respectively). The impacts of aerosol scattering, ground albedo, and relative azimuth on MAX simulations have also been tested. Large discrepancies appear for the aerosol effect, suggesting differences between models in the treatment of the aerosol scattering. A better agreement is obtained in the case of the ground albedo and relative azimuth effects. In zenith-sky geometry, the different models agree generally well, especially below 90° SZA. At higher SZA, larger discrepancies are observed with relative difference values between 2% and 14% in some cases. All the initialization data and results have been made publicly available through the QUILT project web site (http://nadir.nilu.no/quilt/), enabling the testing of other RT codes designed for the calculation of SCDs/AMFs.

scholarly journals Retrieval of tropospheric aerosol, NO<sub>2</sub> and HCHO vertical profiles from MAX-DOAS observations over Thessaloniki, Greece

2021 ◽  
Author(s):  
Dimitris Karagkiozidis ◽  
Martina Michaela Friedrich ◽  
Steffen Beirle ◽  
Alkiviadis Bais ◽  
François Hendrick ◽  
...  
Keyword(s):  
Estimation Method ◽  
Correlation Coefficients ◽  
Scaling Factor ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Systematic Bias ◽  
Vertical Profiles ◽  
Ancillary Data ◽  
Tropospheric Aerosol ◽  
Good Agreement

Abstract. In this study we focus on the retrieval of aerosol and trace gas vertical profiles from Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations for the first time over Thessaloniki, Greece. We use two independent inversion algorithms for the profile retrievals: The Mexican MAX-DOAS Fit (MMF) and the Mainz Profile Algorithm (MAPA). The former is based on the Optimal Estimation Method (OEM), while the latter follows a parameterization approach. We evaluate the performance of MMF and MAPA and we validate their retrieved products with ancillary data measured by other co-located reference instruments. We find an excellent agreement between the tropospheric column densities of NO2 retrieved by MMF and MAPA (Slope = 1.009, Pearson's correlation coefficient R = 0.982) and a good correlation for the case of HCHO (R = 0.927). For aerosols, we find better agreement for the aerosol optical depths (AODs) in the visible (i.e., at 477 nm), compared to the UV (360 nm) and we show that the agreement strongly depends on the O4 scaling factor that is used in the analysis. The trace gas differential slant column densities (dSCDs), simulated by the forward models, are also in good agreement, except for HCHO, where larger scatter is observed due to the increased spectral noise of the measurements in the UV. The agreement for NO2 and HCHO surface concentrations is similar to the comparison of the integrated columns with slightly decreased correlation coefficients. The AODs retrieved by the MAX-DOAS are validated by comparing them with AOD values measured by a CIMEL sun-photometer and a Brewer spectrophotometer. Four different flagging schemes were applied to the data in order to evaluate their performance. Qualitatively, a generally good agreement is observed for both wavelengths, but we find a systematic bias from the CIMEL and Brewer measurements, due to the limited sensitivity of the MAX-DOAS in retrieving information at higher altitudes, especially in the UV. An in-depth validation of the aerosol vertical profiles retrieved by the MAX-DOAS is not possible since only in very few cases the true aerosol profile is known during the period of study. However, we examine four cases, where the MAX-DOAS provided a generally good estimation of the shape of the profiles retrieved by a co-located multi-wavelength lidar system. The NO2 surface concentrations are validated against in situ observations and the comparison of both MMF and MAPA revealed good agreement with correlation coefficients of R = 0.78 and R = 0.73, respectively. Finally, the effect of the O4 scaling factor is investigated by intercomparing the integrated columns retrieved by the two algorithms and also by comparing the AODs derived by MAPA for different values of the scaling factor with AODs measured by the CIMEL and the Brewer.

scholarly journals Intercomparison of total column ozone data from the Pandora spectrophotometer with Dobson, Brewer, and OMI measurements over Seoul, Korea

2016 ◽  
Author(s):  
Jiyoung Kim ◽  
Jhoon Kim ◽  
Hi-Ku Cho ◽  
Jay Herman ◽  
Sang Seo Park ◽  
...  
Keyword(s):  
Optical Absorption Spectroscopy ◽  
Ozone Monitoring Instrument ◽  
Total Column Ozone ◽  
Monitoring Instrument ◽  
Ozone Monitoring ◽  
The Difference ◽  
Column Ozone ◽  
Observation Times ◽  
Total Column ◽  
Daily Total

Abstract. Daily total column ozone (TCO) measured using the Pandora spectrophotometer (#19) was intercompared with data from the Dobson (#124) and Brewer (#148) spectrophotometers, as well as from the Ozone Monitoring Instrument (OMI), over the 2-year period between March 2012 and March 2014 at Yonsei University, Seoul, Korea. The Pandora TCO measurements are closely correlated with those from the Dobson, Brewer, and OMI instruments with regression coefficients (slopes) of 0.95, 1.00, 0.98 (OMI-TOMS), and 0.97 (OMI-DOAS), respectively, and determination coefficients (R2) of 0.95, 0.97, 0.96 (OMI-TOMS), and 0.95 (OMI-DOAS), respectively. In particular, they show a close agreement with the Brewer TCO measurements, with slope and R2 values of 1.00 and 0.97, respectively. The difference between the Pandora and Dobson data can be explained by smaller amount of Dobson data available to calculate the daily averages, observation times, solar zenith angles, SO2 effect, temperature, and humidity between the two datasets. The difference in the results obtained from the Pandora instrument and Ozone Monitoring Instrument-Differential Optical Absorption Spectroscopy (OMI-DOAS algorithm) can be explained by the dependence on seasonal variations of about ± 2 % and solar zenith angle leading to overestimation by 5 % of OMI-DOAS measurements. For the Dobson measurements in particular, the difference caused by the inconsistency in observation times when compared with the Pandora measurements was up to 12.5 % on 22 June 2013 because of diurnal variations in the TCO values. However, despite these various differences and discrepancies, the daily TCO values measured by the four instruments during the 2-year study period are accurate and closely correlated.

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