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T. Verhoelst, J. Granville, F. Hendrick, U. Köhler, C. Lerot, J.-P. Pommereau, A. Redondas, M. Van Roozendael, J.-C. Lambert. (2015). Metrology of ground-based satellite validation: co-location mismatch and smoothing issues of total ozone comparisons (Vol. 8).
Abstract: Abstract. Comparisons with ground-based correlative measurements constitute a key component in the validation of satellite data on atmospheric composition. The error budget of these comparisons contains not only the measurement errors but also several terms related to differences in sampling and smoothing of the inhomogeneous and variable atmospheric field. A versatile system for Observing System Simulation Experiments (OSSEs), named OSSSMOSE, is used here to quantify these terms. Based on the application of pragmatic observation operators onto high-resolution atmospheric fields, it allows a simulation of each individual measurement, and consequently, also of the differences to be expected from spatial and temporal field variations between both measurements making up a comparison pair. As a topical case study, the system is used to evaluate the error budget of total ozone column (TOC) comparisons between GOME-type direct fitting (GODFITv3) satellite retrievals from GOME/ERS2, SCIAMACHY/Envisat, and GOME-2/MetOp-A, and ground-based direct-sun and zenith–sky reference measurements such as those from Dobsons, Brewers, and zenith-scattered light (ZSL-)DOAS instruments, respectively. In particular, the focus is placed on the GODFITv3 reprocessed GOME-2A data record vs. the ground-based instruments contributing to the Network for the Detection of Atmospheric Composition Change (NDACC). The simulations are found to reproduce the actual measurements almost to within the measurement uncertainties, confirming that the OSSE approach and its technical implementation are appropriate. This work reveals that many features of the comparison spread and median difference can be understood as due to metrological differences, even when using strict co-location criteria. In particular, sampling difference errors exceed measurement uncertainties regularly at most mid- and high-latitude stations, with values up to 10 % and more in extreme cases. Smoothing difference errors only play a role in the comparisons with ZSL-DOAS instruments at high latitudes, especially in the presence of a polar vortex due to the strong TOC gradient it induces. At tropical latitudes, where TOC variability is lower, both types of errors remain below about 1 % and consequently do not contribute significantly to the comparison error budget. The detailed analysis of the comparison results, including the metrological errors, suggests that the published random measurement uncertainties for GODFITv3 reprocessed satellite data are potentially overestimated, and adjustments are proposed here. This successful application of the OSSSMOSE system to close for the first time the error budget of TOC comparisons, bodes well for potential future applications, which are briefly touched upon.
Programme: 209
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Baray J-L, Courcoux Y, Keckhut P, Portafaix T, Tulet P, Cammas J-P, Hauchecorne A, Godin Beekmann S, De Mazière M, Hermans C, Desmet F, Sellegri K, Colomb A, Ramonet M, Sciare J, Vuillemin C, Hoareau C, Dionisi D, Duflot V, Vérèmes H, Porteneuve J, Gabarrot F, Gaudo T, Metzger J-M, Payen G, Leclair de Bellevue J, Barthe C, Posny F, Ricaud P, Abchiche A, Delmas R, . (2013). Maïdo observatory: a new high-altitude station facility at Reunion Island (21° S, 55° E) for long-term atmospheric remote sensing and in situ measurements
. ATMOSPHERIC CHEMISTRY AND PHYSICS, 6(10), 2865–2877.
Abstract: Since the nineties, atmospheric measurement systems have been deployed at Reunion Island, mainly for monitoring the atmospheric composition in the framework of NDSC/NDACC (Network for the Detection of Stratospheric Change/Network for the Detection of Atmospheric Composition Change). The location of Reunion Island presents a great interest because there are very few multi-instrumented stations in the tropics and particularly in the southern hemisphere. In 2012, a new observatory was commissioned in Maïdo at 2200 m above sea level: it hosts various instruments for atmospheric measurements, including lidar systems, spectro-radiometers and in situ gas and aerosol measurements.
Programme: 415
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Smirnov A, Sayer A M, Holben B N, Hsu N C, Sakerin S M, Macke A, Nelson N B, Courcoux Y, Smyth T J, Croot P, Quinn P K, Sciare J, Gulev S K, Piketh S, Losno R, Kinne S, Radionov V F, . (2012). Effect of wind speed on aerosol optical depth over remote oceans, based on data from the Maritime Aerosol Network
. Atmos. Meas. Tech., 5(2), 377–388.
Abstract: The Maritime Aerosol Network (MAN) has been collecting data over the oceans since November 2006. The MAN archive provides a valuable resource for aerosol studies in maritime environments. In the current paper we investigate correlations between ship-borne aerosol optical depth (AOD) and near-surface wind speed, either measured (onboard or from satellite) or modeled (NCEP). According to our analysis, wind speed influences columnar aerosol optical depth, although the slope of the linear regression between AOD and wind speed is not steep (~0.004–0.005), even for strong winds over 10 m s−1. The relationships show significant scatter (correlation coefficients typically in the range 0.3–0.5); the majority of this scatter can be explained by the uncertainty on the input data. The various wind speed sources considered yield similar patterns. Results are in good agreement with the majority of previously published relationships between surface wind speed and ship-based or satellite-based AOD measurements. The basic relationships are similar for all the wind speed sources considered; however, the gradient of the relationship varies by around a factor of two depending on the wind data used.
Programme: 415
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Smirnov A, Holben B N, Giles D M, Slutsker I, O'Neill N T, Eck T F, Macke A, Croot P, Courcoux Y, Sakerin S M, Smyth T J, Zielinski T, Zibordi G, Goes J I, Harvey M J, Quinn P K, Nelson N B, Radionov V F, Duarte C M, Losno R, Sciare J, Voss K J, Kinne S, Nalli N R, Joseph E, Krishna Moorthy K, Covert D S, Gulev S K, Milinevsky G, Larouche P, Belanger S, Horne E, Chin M, Remer L A, Kahn R A, Reid J S, Schulz M, Heald C L, Zhang J, Lapina K, Kleidman R G, Griesfeller J, Gaitley B J, Tan Q, Diehl T L, . (2011). Maritime aerosol network as a component of AERONET first results and comparison with global aerosol models and satellite retrievals
. 1867-1381, 4(3), 583–597.
Abstract: The Maritime Aerosol Network (MAN) has been collecting data over the oceans since November 2006. Over 80 cruises were completed through early 2010 with deployments continuing. Measurement areas included various parts of the Atlantic Ocean, the Northern and Southern Pacific Ocean, the South Indian Ocean, the Southern Ocean, the Arctic Ocean and inland seas. MAN deploys Microtops handheld sunphotometers and utilizes a calibration procedure and data processing traceable to AERONET. Data collection included areas that previously had no aerosol optical depth (AOD) coverage at all, particularly vast areas of the Southern Ocean. The MAN data archive provides a valuable resource for aerosol studies in maritime environments. In the current paper we present results of AOD measurements over the oceans, and make a comparison with satellite AOD retrievals and model simulations.
Programme: 415
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van der Laan-Luijkx I T, Neubert R E M, van der Laan S, Meijer H A J, . (2010). Continuous measurements of atmospheric oxygen and carbon dioxide on a North Sea gas platform
. Atmos. Meas. Tech., 3(1), 113–125.
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Tijl Verhoelst, Steven Compernolle, Gaia Pinardi, Jean-Christopher Lambert, Henk J. Eskes, Kai-Uwe Eichmann, Ann Mari Fjæraa, José Granville, Sander Niemeijer, Alexander Cede, Martin Tiefengraber, François Hendrick, Andrea Pazmiño, Alkiviadis Bais, Ariane Bazureau, K. Folkert Boersma, Kristof Bognar, Angelika Dehn, Sebastian Donner, Aleksandr Elokhov, Manuel Gebetsberger, Florence Goutail, Michel Grutter de la Mora, Aleksandr Gruzdev, Myrto Gratsea, Georg H. Hansen, Hitoshi Irie, Nis Jepsen, Yugo Kanaya, Dimitris Karagkiozidis, Rigel Kivi, Karin Kreher, Pieternel F. Levelt, Cheng Liu, Moritz Müller, Monica Navarro Comas, Ankie J. M. Piters, Jean-Pierre Pommereau, Thierry Portafaix, Cristina Prados-Roman, Olga Puentedura, Richard Querel, Julia Remmers, Andreas Richter, John Rimmer, Claudia Rivera Cárdenas, Lidia Saavedra de Miguel, Valery P. Sinyakov, Wolfgang Stremme, Kimberly Strong, Michel Van Roozendael, J. Pepijn Veefkind, Thomas Wagner, Folkard Wittrock, Margarita Yela González, Claus Zehner. (2021). Ground-based validation of the Copernicus Sentinel-5P TROPOMI NO2 measurements with the NDACC ZSL-DOAS, MAX-DOAS and Pandonia global networks (Vol. 14).
Abstract: This Paper Reports On Consolidated Ground-based Validation Results Of The Atmospheric No2 Data Produced Operationally Since April 2018 By The Tropospheric Monitoring Instrument (Tropomi) On Board Of The Esa/eu Copernicus Sentinel-5 Precursor (S5p) Satellite. Tropospheric, Stratospheric, And Total No2 Column Data From S5p Are Compared To Correlative Measurements Collected From, Respectively, 19 Multi-axis Differential Optical Absorption Spectroscopy (Max-doas), 26 Network For The Detection Of Atmospheric Composition Change (Ndacc) Zenith-scattered-light Doas (Zsl-doas), And 25 Pandonia Global Network (Pgn)/pandora Instruments Distributed Globally. The Validation Methodology Gives Special Care To Minimizing Mismatch Errors Due To Imperfect Spatio-temporal Co-location Of The Satellite And Correlative Data, E.g. By Using Tailored Observation Operators To Account For Differences In Smoothing And In Sampling Of Atmospheric Structures And Variability And Photochemical Modelling To Reduce Diurnal Cycle Effects. Compared To The Ground-based Measurements, S5p Data Show, On Average, (I) A Negative Bias For The Tropospheric Column Data, Of Typically −23 % To −37 % In Clean To Slightly Polluted Conditions But Reaching Values As High As −51 % Over Highly Polluted Areas; (Ii) A Slight Negative Median Difference For The Stratospheric Column Data, Of About −0.2 Pmolec Cm−2, I.e. Approx. −2 % In Summer To −15 % In Winter; And (Iii) A Bias Ranging From Zero To −50 % For The Total Column Data, Found To Depend On The Amplitude Of The Total No2 Column, With Small To Slightly Positive Bias Values For Columns Below 6 Pmolec Cm−2 And Negative Values Above. The Dispersion Between S5p And Correlative Measurements Contains Mostly Random Components, Which Remain Within Mission Requirements For The Stratospheric Column Data (0.5 Pmolec Cm−2) But Exceed Those For The Tropospheric Column Data (0.7 Pmolec Cm−2). While A Part Of The Biases And Dispersion May Be Due To Representativeness Differences Such As Different Area Averaging And Measurement Times, It Is Known That Errors In The S5p Tropospheric Columns Exist Due To Shortcomings In The (Horizontally Coarse) A Priori Profile Representation In The Tm5-mp Chemical Transport Model Used In The S5p Retrieval And, To A Lesser Extent, To The Treatment Of Cloud Effects And Aerosols. Although Considerable Differences (Up To 2 Pmolec Cm−2 And More) Are Observed At Single Ground-pixel Level, The Near-real-time (Nrti) And Offline (Offl) Versions Of The S5p No2 Operational Data Processor Provide Similar No2 Column Values And Validation Results When Globally Averaged, With The Nrti Values Being On Average 0.79 % Larger Than The Offl Values.
Programme: 209
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Katerina Garane, Maria-Elissavet Koukouli, Tijl Verhoelst, Christophe Lerot, Klaus-Peter Heue, Vitali Fioletov, Dimitrios Balis, Alkiviadis Bais, Ariane Bazureau, Angelika Dehn, Florence Goutail, Jose Granville, Debora Griffin, Daan Hubert, Arno Keppens, Jean-Christopher Lambert, Diego Loyola, Chris McLinden, Andrea Pazmino, Jean-Pierre Pommereau, Alberto Redondas, Fabian Romahn, Pieter Valks, Michel Van Roozendael, Jian Xu, Claus Zehner, Christos Zerefos, Walter Zimmer. (2019). TROPOMI/S5P total ozone column data: global ground-based validation and consistency with other satellite missions (Vol. 12).
Abstract: Abstract. In October 2017, the Sentinel-5 Precursor (S5P) mission was launched, carrying the TROPOspheric Monitoring Instrument (TROPOMI), which provides a daily global coverage at a spatial resolution as high as 7 km × 3.5 km and is expected to extend the European atmospheric composition record initiated with GOME/ERS-2 in 1995, enhancing our scientific knowledge of atmospheric processes with its unprecedented spatial resolution. Due to the ongoing need to understand and monitor the recovery of the ozone layer, as well as the evolution of tropospheric pollution, total ozone remains one of the leading species of interest during this mission. In this work, the TROPOMI near real time (NRTI) and offline (OFFL) total ozone column (TOC) products are presented and compared to daily ground-based quality-assured Brewer and Dobson TOC measurements deposited in the World Ozone and Ultraviolet Radiation Data Centre (WOUDC). Additional comparisons to individual Brewer measurements from the Canadian Brewer Network and the European Brewer Network (Eubrewnet) are performed. Furthermore, twilight zenith-sky measurements obtained with ZSL-DOAS (Zenith Scattered Light Differential Optical Absorption Spectroscopy) instruments, which form part of the SAOZ network (Système d'Analyse par Observation Zénitale), are used for the validation. The quality of the TROPOMI TOC data is evaluated in terms of the influence of location, solar zenith angle, viewing angle, season, effective temperature, surface albedo and clouds. For this purpose, globally distributed ground-based measurements have been utilized as the background truth. The overall statistical analysis of the global comparison shows that the mean bias and the mean standard deviation of the percentage difference between TROPOMI and ground-based TOC is within 0 –1.5 % and 2.5 %–4.5 %, respectively. The mean bias that results from the comparisons is well within the S5P product requirements, while the mean standard deviation is very close to those limits, especially considering that the statistics shown here originate both from the satellite and the ground-based measurements. Additionally, the TROPOMI OFFL and NRTI products are evaluated against already known spaceborne sensors, namely, the Ozone Mapping Profiler Suite, on board the Suomi National Polar-orbiting Partnership (OMPS/Suomi-NPP), NASA v2 TOCs, and the Global Ozone Monitoring Experiment 2 (GOME-2), on board the Metop-A (GOME-2/Metop-A) and Metop-B (GOME-2/Metop-B) satellites. This analysis shows a very good agreement for both TROPOMI products with well-established instruments, with the absolute differences in mean bias and mean standard deviation being below +0.7 % and 1 %, respectively. These results assure the scientific community of the good quality of the TROPOMI TOC products during its first year of operation and enhance the already prevalent expectation that TROPOMI/S5P will play a very significant role in the continuity of ozone monitoring from space.
Programme: 209
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A. El Yazidi, M. Ramonet, P. Ciais, G. Broquet, I. Pison, A. Abbaris, D. Brunner, S. Conil, M. Delmotte, F. Gheusi, F. Guerin, L. Hazan, N. Kachroudi, G. Kouvarakis, N. Mihalopoulos, L. Rivier, D. Serça. (2017). Identification of spikes associated with local sources in continuous time series of atmospheric CO, CO2 and CH4 (Vol. 11).
Abstract: This study deals with the problem of identifying atmospheric data influenced by local emissions that can result in spikes in time series of greenhouse gases and long-lived tracer measurements. We considered three spike detection methods known as coefficient of variation (COV), robust extraction of baseline signal (REBS) and standard deviation of the background (SD) to detect and filter positive spikes in continuous greenhouse gas time series from four monitoring stations representative of the European ICOS (Integrated Carbon Observation System) Research Infrastructure network. The results of the different methods are compared to each other and against a manual detection performed by station managers. Four stations were selected as test cases to apply the spike detection methods: a continental rural tower of 100 m height in eastern France (OPE), a high-mountain observatory in the south-west of France (PDM), a regional marine background site in Crete (FKL) and a marine clean-air background site in the Southern Hemisphere on Amsterdam Island (AMS). This selection allows us to address spike detection problems in time series with different variability. Two years of continuous measurements of CO2, CH4 and CO were analysed. All methods were found to be able to detect short-term spikes (lasting from a few seconds to a few minutes) in the time series. Analysis of the results of each method leads us to exclude the COV method due to the requirement to arbitrarily specify an a priori percentage of rejected data in the time series, which may over- or underestimate the actual number of spikes. The two other methods freely determine the number of spikes for a given set of parameters, and the values of these parameters were calibrated to provide the best match with spikes known to reflect local emissions episodes that are well documented by the station managers. More than 96 % of the spikes manually identified by station managers were successfully detected both in the SD and the REBS methods after the best adjustment of parameter values. At PDM, measurements made by two analyzers located 200 m from each other allow us to confirm that the CH4 spikes identified in one of the time series but not in the other correspond to a local source from a sewage treatment facility in one of the observatory buildings. From this experiment, we also found that the REBS method underestimates the number of positive anomalies in the CH4 data caused by local sewage emissions. As a conclusion, we recommend the use of the SD method, which also appears to be the easiest one to implement in automatic data processing, used for the operational filtering of spikes in greenhouse gases time series at global and regional monitoring stations of networks like that of the ICOS atmosphere network.
Programme: 416
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Katerina Garane, Christophe Lerot, Melanie Coldewey-Egbers, Tijl Verhoelst, Maria Elissavet Koukouli, Irene Zyrichidou, Dimitris S. Balis, Thomas Danckaert, Florence Goutail, Jose Granville, Daan Hubert, Arno Keppens, Jean-Christopher Lambert, Diego Loyola, Jean-Pierre Pommereau, Michel Van Roozendael, Claus Zehner. (2018). Quality assessment of the Ozone_cci Climate Research Data Package (release 2017) – Part 1: Ground-based validation of total ozone column data products (Vol. 11).
Abstract: The Gome-type Total Ozone Essential Climate Variable (Gto-ecv) Is A Level-3 Data Record, Which Combines Individual Sensor Products Into One Single Cohesive Record Covering The 22-year Period From 1995 To 2016, Generated In The Frame Of The European Space Agency's Climate Change Initiative Phase Ii. It Is Based On Level-2 Total Ozone Data Produced By The Godfit (Gome-type Direct Fitting) V4 Algorithm As Applied To The Gome/ers-2, Omi/aura, Sciamachy/envisat And Gome-2/metop-a And Metop-b Observations. In This Paper We Examine Whether Gto-ecv Meets The Specific Requirements Set By The International Climate–chemistry Modelling Community For Decadal Stability Long-term And Short-term Accuracy. In The Following, We Present The Validation Of The 2017 Release Of The Climate Research Data Package Total Ozone Column (Crdp Toc) At Both Level 2 And Level 3. The Inter-sensor Consistency Of The Individual Level-2 Data Sets Has Mean Differences Generally Within 0.5% At Moderate Latitudes (±50°), Whereas The Level-3 Data Sets Show Mean Differences With Respect To The Omi Reference Data Record That Span Between −0.2±0.9% (For Gome-2b) And 1.0±1.4% (For Sciamachy). Very Similar Findings Are Reported For The Level-2 Validation Against Independent Ground-based Toc Observations Reported By Brewer, Dobson And Saoz Instruments: The Mean Bias Between Godfit V4 Satellite Toc And The Ground Instrument Is Well Within 1.0±1.0% For All Sensors, The Drift Per Decade Spans Between −0.5% And 1.0±1.0% Depending On The Sensor, And The Peak-to-peak Seasonality Of The Differences Ranges From ∼ 1% For Gome And Omi To ∼ 2% For Sciamachy. For The Level-3 Validation, Our First Goal Was To Show That The Level-3 Crdp Produces Findings Consistent With The Level-2 Individual Sensor Comparisons. We Show A Very Good Agreement With 0.5 To 2% Peak-to-peak Amplitude For The Monthly Mean Difference Time Series And A Negligible Drift Per Decade Of The Differences In The Northern Hemisphere Of −0.11±0.10%decade−1 For Dobson And +0.22±0.08%decade−1 For Brewer Collocations. The Exceptional Quality Of The Level-3 Gto-ecv V3 Toc Record Temporal Stability Satisfies Well The Requirements For The Total Ozone Measurement Decadal Stability Of 1–3% And The Short-term And Long-term Accuracy Requirements Of 2 And 3%, Respectively, Showing A Remarkable Inter-sensor Consistency, Both In The Level-2 Godfit V4 And In The Level-3 Gto-ecv V3 Datasets, And Thus Can Be Used For Longer-term Analysis Of The Ozone Layer, Such As Decadal Trend Studies, Chemistry–climate Model Evaluation And Data Assimilation Applications.
Programme: 209
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Bès de Berc M, Grunberg M, Engels F, . (2015). How to create a very-low-cost, very-low-power, credit-card-sized and real-time-ready datalogger
(Vol. 40). Copernicus GmbH.
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