D. P. Edwards

National Center for Atmospheric Research, Boulder, CO, United States

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Publications (117)193.62 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: [1] Validation results are reported for the MOPITT (Measurements of Pollution in the Troposphere) “Version 5” (V5) product for tropospheric carbon monoxide (CO) and are compared to results for the “Version 4” product. The V5 retrieval algorithm introduces (1) a method for reducing retrieval bias drift associated with long-term instrumental degradation, (2) a more exact representation of the effects of random errors in the radiances and, for the first time, (3) the use of MOPITT's near-infrared (NIR) radiances to complement the thermal-infrared (TIR) radiances. Exploiting TIR and NIR radiances together facilitates retrievals of CO in the lowermost troposphere. V5 retrieval products based (1) solely on TIR measurements, (2) solely on NIR measurements and (3) on both TIR and NIR measurements are separately validated and analyzed. Actual retrieved CO profiles and total columns are compared with equivalent retrievals based on in situ measurements from (1) routine NOAA aircraft sampling mainly over North America and (2) the “HIAPER Pole to Pole Observations” (HIPPO) field campaign. Particular attention is focused on the long-term stability and geographical uniformity of the retrieval errors. Results for the retrieved total column clearly indicate reduced temporal bias drift in the V5 products compared to the V4 product, and do not exhibit a positive bias in the Southern Hemisphere, which is evident in the V4 product.
    Journal of Geophysical Research: Atmospheres. 06/2013; 118(12).
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    ABSTRACT: Practical implementations of chemical OSSEs (Observing System Simulation Experiments) usually rely on approximations of the pseudo-observations by means of a prior parametrization of the averaging kernels, which describe the sensitivity of the observing systems to the target atmospheric species. This is intended to avoid the need for use of a computationally expensive pseudo-observations simulator that relies on full radiative transfer calculations. Here we present an investigation on how no, or limited, scene dependent averaging kernels parametrizations may misrepresent the sensitivity of an observing system, and thus possibly lead to inaccurate results of OSSEs. We carried out the full radiative transfer calculation for a three-days period over Europe, to produce reference pseudo-observations of lower tropospheric ozone, as they would be observed by a concept geostationary observing system called MAGEAQ (Monitoring the Atmosphere from Geostationary orbit for European Air Quality). The selected spatiotemporal interval is characterized by a peculiar ozone pollution event. We then compared our reference with approximated pseudo-observations, following existing simulation exercises made for both the MAGEAQ and GEOstationary Coastal and Air Pollution Events (GEO-CAPE) missions. We found that approximated averaging kernels may fail to replicate the variability of the full radiative transfer calculations. Then, we compared the full radiative transfer and the approximated pseudo-observations during a pollution event. We found that the approximations substantially overestimate the capability of the MAGEAQ to follow the spatiotemporal variations of the lower tropospheric ozone in selected areas. We conclude that such approximations may lead to false conclusions if used in an OSSE. Thus, we recommend to use comprehensive scene-dependent approximations of the averaging kernels, in cases where the full radiative transfer is computationally too costly for the OSSE being investigated.
    Atmospheric Measurement Techniques Discussions. 03/2013; 6(2):2413-2448.
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    ABSTRACT: A current obstacle to the Observation System Simulation Experiments (OSSEs) used to quantify the potential performance of future atmospheric composition remote sensing systems is a computationally efficient method to define the scene-dependent vertical sensitivity of measurements as expressed by the retrieval averaging kernels (AKs). We present a method for the efficient prediction of AKs for multispectral retrievals of carbon monoxide (CO) and ozone (O3) based on actual retrievals from MOPITT on EOS-Terra and TES and OMI on EOS-Aura, respectively. This employs a multiple regression approach for deriving scene-dependent AKs using predictors based on state parameters such as the thermal contrast between the surface and lower atmospheric layers, trace gas volume mixing ratios (VMR), solar zenith angle, water vapor amount, etc. We first compute the singular vector decomposition (SVD) for individual cloud-free AKs and retain the 1st three ranked singular vectors in order to fit the most significant, orthogonal components of the AK in the subsequent multiple regression on a training set of retrieval cases. The resulting fit coefficients are applied to the predictors from a different test set of retrievals cased to reconstruct predicted AKs, which can then be evaluated against the true test set retrieval AKs. By comparing the VMR profile adjustment resulting from the use of the predicted vs. true AKs, we quantify the CO and O3 VMR profile errors associated with the use of the predicted AKs compared to the true AKs that might be obtained from a computationally expensive full retrieval calculation as part of an OSSE. Similarly, we estimate the errors in CO and O3 VMRs from using a single regional average AK to represent all retrievals, which has been a common approximation in chemical OSSEs performed to-date. For both CO and O3 in the lower troposphere, we find a significant reduction in error when using the predicted AKs as compared to a single average AK. This study examined data from the continental United States (CONUS) for 2006, but the approach could be applied to other regions and times.
    Atmospheric Measurement Techniques Discussions. 03/2013; 6(2):2751-2791.
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    ABSTRACT: Atmospheric carbon monoxide (CO) distributions are controlled by anthropogenic emissions, biomass burning, transport and oxidation by reaction with the hydroxyl radical (OH). Quantifying trends in CO is therefore important for understanding changes related to all of these contributions. Here we present a comprehensive record of satellite observations from 2000 through 2011 of total column CO using the available measurements from nadir-viewing thermal infrared instruments: MOPITT, AIRS, TES and IASI. We examine trends for CO in the Northern and Southern Hemispheres along with regional trends for Eastern China, Eastern USA, Europe and India. We find that all the satellite observations are consistent with a modest decreasing trend ∼-1% yr-1 in total column CO over the Northern Hemisphere for this time period and a less significant, but still decreasing trend in the Southern Hemisphere. Although decreasing trends in the United States and Europe have been observed from surface CO measurements, we also find a decrease in CO over E. China that, to our knowledge, has not been reported previously. Some of the interannual variability in the observations can be explained by global fire emissions, but the overall decrease needs further study to understand the implications for changes in anthropogenic emissions.
    Atmospheric Chemistry and Physics 01/2013; 13(2):837-850. · 4.88 Impact Factor
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    ABSTRACT: The new Version 5 MOPITT (Measurements of Pollution in the Troposphere) product for carbon monoxide (CO) is the first satellite product to exploit simultaneous near-infrared and thermal-infrared observations to enhance retrieval sensitivity in the lower troposphere. This feature is important to air quality analyses and studies of CO sources. However, because of the influence of both thermal contrast and geophysical noise, the retrieval characteristics for this new multispectral product are highly variable. New V5 products for surface-level CO concentrations have been evaluated over the contiguous United States using both in situ vertical profiles and NOAA ground-based "Tall Tower" measurements. Validation results based on the in situ profiles indicate that retrieval biases are on the order of a few percent. However, direct comparisons with the Tall Tower measurements demonstrate that smoothing error, which depends on both the retrieval averaging kernels and CO variability in the lower troposphere, exhibits significant geographical and seasonal variability.
    Journal of Geophysical Research 07/2012; 117(D13):13306-. · 3.17 Impact Factor
  • A. Boynard, G. Pfister, D. P. Edwards
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    ABSTRACT: As a tracer of pollution and a precursor of tropospheric ozone, carbon monoxide (CO) is a key species for studying air quality. This pollutant is highly variable and the integration of observations and modelling can provide a better insight into, for example, pollution episode development and pollution transport on regional to global scales. In this work, we analyse CO concentrations simulated by the WRF chem regional model over the U.S. during the summer 2008 in order to characterize its geographical and temporal variations at the surface, in the lowermost troposphere and in the free troposphere. The model is evaluated by comparisons with surface measurements available from several EPA ground-based stations over the U.S. and satellite observations from Terra/MOPITT. CO tracers for different emission sources are also used to differentiate the variability due to dynamics, photochemistry and emissions and to assess the CO budget. Finally, we compare the representation of surface and planetary boundary layer CO concentration variability that would be captured by representative satellite sensor observations using the different CO spectral bands. These comprise thermal infrared measurements sensitive primarily to the free troposphere concentration, near-infrared measurements sensitive to the total column and combined multispectral measurements that would provide sensitivity to the lowermost troposphere concentration.
    AGU Fall Meeting Abstracts. 12/2011;
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    ABSTRACT: The Geostationary Coastal and Air Pollution Events (GEO-CAPE) mission is required to be able to measure ozone with two degrees of freedom for signal (DFS) in the troposphere, and to provide sensitivity in the lowest 2 km (lowermost troposphere, LMT). We explore the feasibility of using multispectral measurements from the ultraviolet (UV) to the thermal infrared (TIR) to improve LMT ozone retrievals compared to conventional retrievals employing only the UV or the TIR. Simulations spanning a range of ozone mixing ratios indicate that the combination of UV, visible and TIR significantly improves the total column DFS as well as the LMT DFS. We will present results both for clear sky scenarios and those containing realistic cloud and aerosol loadings.
    AGU Fall Meeting Abstracts. 12/2011;
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    ABSTRACT: Carbon monoxide (CO) is an important trace gas for understanding air quality and atmospheric composition. It is a good tracer of pollution plumes and atmospheric dynamics. In this talk we describe the analysis of global and regional CO distributions as seen by both the MOPITT/Terra and IASI/MetOp missions, from mid-2007 up to now. Long term trends for IASI and MOPITT (version 3, 4 and 5) CO total columns over specific areas are presented, and show excellent agreement. CO distributions over polluted and clean regions are compared. Preliminary results of a study comparing the surface CO level for the two sounders over different cities will be presented, using MOPITT version 5 products that include the NIR and show a better sensitivity near the ground. Finally, this talk will also illustrate how the data processed at ULB-LATMOS are currently assimilated in the MACC project in near-real time in order to generate the CO pollution forecasts over Europe. Surface CO obtained after assimilation show better agreement with ground-based station measurements.
    AGU Fall Meeting Abstracts. 12/2011;
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    ABSTRACT: The new MOPITT Version 5 product is the first satellite product for carbon monoxide (CO) to exploit multispectral observations. Together, near-infrared (NIR) and thermal-infrared (TIR) observations permit the retrieval of CO concentrations in the lower troposphere, near the actual sources. However, while this feature is potentially valuable for applications including chemical weather forecasting and inverse modeling, the retrieval characteristics of the new multispectral product (e.g., the retrieval averaging kernels) are highly variable. The underlying causes of this variability include thermal contrast and geophysical noise. Validating the new V5 product is challenging for several reasons. Compared to the TIR-only MOPITT product, random retrieval errors in the multispectral product are substantially larger. To compensate, stronger temporal and spatial averaging may be necessary. However, the temporal and spatial variability of CO in the planetary boundary layer (PBL) are much greater than in the free troposphere. Consequently, in-situ CO measurements made in the PBL may be poorly correlated with CO concentrations averaged over areas representative of MOPITT pixels (~ 22 km). Errors from this effect are only compounded as multiple MOPITT pixels are averaged together, particularly if there are significant regional sources. Previous MOPITT validation efforts have relied mainly on in-situ profiles measured from aircraft. While these are valuable, we are also exploring new sources of validation data. For example, we have begun comparing MOPITT retrieval results with CO in-situ measurements from the NOAA 'Tall Tower' network. Instruments on these towers measure CO concentrations at high temporal frequency and at multiple fixed altitudes within the PBL.
    AGU Fall Meeting Abstracts. 12/2011;
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    ABSTRACT: In this paper, we analyze tropospheric O3 together with HNO3 during the POLARCAT (Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, of Climate, Chemistry, Aerosols, and Transport) program, combining observations and model results. Aircraft observations from the NASA ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites) and NOAA ARCPAC (Aerosol, Radiation and Cloud Processes affecting Arctic Climate) campaigns during spring and summer of 2008 are used together with the Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4) to assist in the interpretation of the observations in terms of the source attribution and transport of O3 and HNO3 into the Arctic. The MOZART-4 simulations reproduce the aircraft observations generally well (within 15 %), but some discrepancies in the model are identified and discussed. The observed correlation of O3 with HNO3 is exploited to evaluate the MOZART-4 model performance for different air mass types (fresh plumes, free troposphere and stratospheric-contaminated air masses). Based on model simulations of O3 and HNO3 tagged by source type and region, we find that the anthropogenic pollution from the Northern Hemisphere is the dominant source of O3 and HNO3 in the Arctic at pressure greater than 400 hPa, and that the stratospheric influence is the principal contribution at pressures less 400 hPa. During the summer, intense Russian fire emissions contribute some amount to the tropospheric columns of both gases over the American sector of the Arctic. North American fire emissions (California and Canada) also show an important impact on tropospheric ozone in the Arctic boundary layer. Additional analysis of tropospheric O3 measurements from ground-based FTIR and from the IASI satellite sounder made at the Eureka (Canada) and Thule (Greenland) polar sites during POLARCAT has been performed using the tagged contributions. It demonstrates the capability of these instruments for observing pollution at Northern high latitudes. Differences between contributions from the sources to the tropospheric columns as measured by FTIR and IASI are discussed in terms of vertical sensitivity associated with these instruments. The first analysis of O3 tropospheric columns observed by the IASI satellite instrument over the Arctic is also provided. Despite its limited vertical sensitivity in the lowermost atmospheric layers, we demonstrate that IASI is capable of detecting low-altitude pollution transported into the Arctic with some limitations.
    Atmospheric Chemistry and Physics 08/2011; 11(8):23707-23760. · 4.88 Impact Factor
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    ABSTRACT: This paper describes the capabilities of a nadir thermal infrared (TIR) sensor proposed for deployment onboard a geostationary platform to monitor ozone (O3) and carbon monoxide (CO) for air quality (AQ) purposes. To assess the capabilities of this sensor we perform idealized retrieval studies considering typical atmospheric profiles of O3 and CO over Europe with different instrument configuration (signal to noise ratio, SNR, and spectral sampling interval, SSI) using the KOPRA forward model and the KOPRA-fit retrieval scheme. We then select a configuration, referred to as GEO-TIR, optimized for providing information in the lowermost troposphere (LmT; 0-3 km in height). For the GEO-TIR configuration we obtain ~1.5 degrees of freedom for O3 and ~2 for CO at altitudes between 0 and 15 km. The error budget of GEO-TIR, calculated using the principal contributions to the error (namely, temperature, measurement error, smoothing error) shows that information in the LmT can be achieved by GEO-TIR. We also retrieve analogous profiles from another geostationary infrared instrument with SNR and SSI similar to the Meteosat Third Generation Infrared Sounder (MTG-IRS) which is dedicated to numerical weather prediction, referred to as GEO-TIR2. We quantify the added value of GEO-TIR over GEO-TIR2 for a realistic atmosphere, simulated using the chemistry transport model MOCAGE (MOdèle de Chimie Atmospherique à Grande Echelle). Results show that GEO-TIR is able to capture well the spatial and temporal variability in the LmT for both O3 and CO. These results also provide evidence of the significant added value in the LmT of GEO-TIR compared to GEO-TIR2 by showing GEO-TIR is closer to MOCAGE than GEO-TIR2 for various statistical parameters (correlation, bias, standard deviation).
    Atmospheric Measurement Techniques 01/2011; 4:297-317. · 3.21 Impact Factor
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    ABSTRACT: Geophysical noise is caused by surface heterogeneity and field of view motionThe MOPITT retrieval algorithm now explicitly accounts for geophysical noiseAlgorithm changes enhance the sensitivity to CO near the surface
    Journal of Geophysical Research 01/2011; 116. · 3.17 Impact Factor
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    ABSTRACT: Air pollution is of concern in many parts of California and is impacted by both local emissions and also by pollution inflow from the Pacific. In this study, we use the regional chemical transport model WRF-Chem V3.2 to examine the CO budget over California. We include model CO tracers for different emission sources in the model, which allow estimating the relative importance of local sources versus pollution inflow on the distribution of CO at the surface and in the free troposphere. The focus of our study is on the 15 June–15 July 2008 time period, which coincides with the aircraft deployment of the NASA Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission over California. Model simulations are evaluated using these aircraft observations as well as satellite retrievals and surface observations of CO. Evaluation results show that the model overall predicts the observed CO fields well, but points towards an underestimate of CO from the fires in Northern California, which had a strong influence during the study period, and towards a slight overestimate of CO from pollution inflow and local anthropogenic sources. The analysis of the CO budget over California reveals that inflow of CO explains on average 53 ± 21% of surface CO during the study period, compared to 22 ± 18% for local anthropogenic sources and 18 ± 22% for fires. In the free troposphere, the average CO contributions are estimated as 78 ± 16% for CO inflow, 6 ± 4% for CO from local anthropogenic sources and 11 ± 13% for CO from fires.
    ATMOSPHERIC CHEMISTRY AND PHYSICS 01/2011; · 5.51 Impact Factor
  • A. Boynard, D. P. Edwards, G. Pfister
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    ABSTRACT: Ozone and carbon monoxide play key roles in the photo-chemical processes occurring in the atmosphere, with strong consequences for tropospheric chemistry, air quality and climate. Both molecules are highly variable, particularly in the troposphere, and need to be accurately monitored in order to provide a better insight into, for example, pollution episode development and pollution transport on regional to global scales. In this work, we analyse ozone and carbon monoxide concentrations simulated by the WRF chem regional model over the USA in order to characterize their geographical and temporal variations at the surface, in the lowermost troposphere and in the free troposphere along with their spatio-temporal correlations. In addition to model sensitivity studies, carbon monoxide tracers for different emission sources are used to differentiate the variability due to dynamics, photochemistry and emissions. We also present comparisons with surface measurements available from several ground-based stations over the USA.
    AGU Fall Meeting Abstracts. 12/2010;
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    ABSTRACT: We present results from a study that quantifies the impacts of various sources on surface air quality over California. The focus of the analysis is on summer 2008, when the ARCTAS-CARB aircraft campaign, a joint program between NASA and the California Air Resources Board took place. The study integrates the global chemistry transport model MOZART-V4 with the regional WRF-Chem model. Both models employ the same chemistry scheme and emissions allowing for a high level of synergy across model scales. The global model provides time and space varying boundary conditions for the regional simulations. Aircraft measurements from the field campaign will be used together with in-situ observations from ground (U.S. EPA Air Quality Monitoring System) as well as satellite retrievals (e.g. Aura/OMI NO2 and HCHO, Aura/TES CO and O3, Terra/MOPITT CO) for evaluating the model simulations and supporting the analysis. Tracer simulations are performed to estimate the relative impacts of anthropogenic emissions, wildfires and pollution inflow on surface air.
    AGU Fall Meeting Abstracts. 12/2010;
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    ABSTRACT: We present initial comparisons of MOPITT multispectral (TIR + NIR) CO measurements with WRF-Chem simulations for the Beijing Olympics in August 2008. The Chinese government made a significant effort to improve air quality during the Olympics by controlling pollution emissions around Beijing before and during Olympics. A new emissions inventory has been created to account for these controls and implemented in WRF-chem. The inventory is specific for pollution sectors such as power, industry, transport and domestic, with corresponding emission factors. By comparing to the MOPITT data, we can test the model predictions for CO and derive improved emissions estimates, then potentially use the emission factors to infer the corresponding reduction in CO2 emissions during the Olympics.
    AGU Fall Meeting Abstracts. 12/2010;
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    ABSTRACT: Reactive nitrogen compounds play an essential role in the processes that control the ozone abundance in the lower atmosphere, in particular HNO3, which is one of the principal reservoir species for the nitrogen oxides. However, there remains a significant lack of data for simultaneous observations of O3 and HNO3, despite the fact that the correlations between these species are particularly important for characterizing air masses and evaluating how ozone depends on nitrogen compounds. As a consequence, the chemical link between O3 and HNO3 remains poorly known in the lower layers. In this study, we use aircraft observations of O3 and HNO3 from the NASA ARCTAS and NOAA ARCPAC campaigns during spring and summer of 2008 together with O3 and NO2 satellite data respectively from the IASI and the OMI instruments and a global chemical transport model (MOZART-4) to better understand the sources, transport and variability of these compounds in the Arctic. FTIR measurements of O3 and HNO3 made at Eureka and Thule during the ARCTAS mission are also used for our analysis. The results are discussed in terms of O3-NOy chemistry and the role of HNO3 as a reservoir of NOx is investigated. These analyses also help us to quantify the contribution of the stratosphere to the tropospheric ozone budget in the Arctic.
    AGU Fall Meeting Abstracts. 12/2010;
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    ABSTRACT: Unlike all other satellite instruments capable of measuring tropospheric concentrations of carbon monoxide (CO), the MOPITT (Measurements of Pollution in the Troposphere) instrument on the Earth Observing System Terra platform makes both near-infrared (NIR) and thermal-infrared (TIR) measurements. In principle, this design allows MOPITT to separately retrieve CO concentrations in the lower troposphere and the middle-upper troposphere. Most existing satellite products for CO, including the current V4 MOPITT product, only exploit TIR observations and primarily provide measurements of CO concentrations in the middle and upper troposphere. Complex instrumental-geophysical noise processes affecting the NIR radiances have, so far, prevented their use in operational MOPITT retrieval products. However, recent analysis of the 'Level 0' instrument data has revealed that the combined effects of (1) motion of the instrumental field of view and (2) sub-pixel variability of the surface reflectance result in a highly variable source of error in the calibrated radiances. An analysis of MODIS radiance variability supports this concept. New 'Version 5' (or V5) MOPITT data processing algorithms have been adapted to quantify this noise term on a pixel by pixel basis and fully account for its effect on the retrieval uncertainties. V5 products based on multispectral (TIR/NIR) observations, featuring enhanced sensitivity to surface-level CO, will soon be produced operationally. An ongoing drought in Russia coupled with anomalous high temperatures produced extensive forest and peat bog fires during the summer of 2010. The resulting pollution created a significant health hazard for residents of large population centers, including Moscow. We will present experimental MOPITT multispectral CO retrieval results over Russia during the summer of 2010. As indicated by the averaging kernels, these retrievals contain at least two independent pieces of CO profile information and exhibit strong sensitivity to boundary-layer CO. Near the fires, surface-level CO concentrations are observed to be many times the background concentration for the region. The presented results demonstrate fundamentally new applications possible with the upcoming V5 MOPITT product.
    AGU Fall Meeting Abstracts. 12/2010;
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    ABSTRACT: This paper describes the capabilities of a nadir thermal infrared (TIR) sensor proposed for embarkation onboard a geostationary platform to monitor ozone (O3) and carbon monoxide (CO) for air quality (AQ) purposes. To assess the capabilities of this sensor we perform idealized retrieval studies considering typical atmospheric profiles of O3 and CO over Europe with different instrument configurations (signal to noise ratio and spectral sampling interval) using the KOPRA forward model and the KOPRA-fit retrieval scheme based on the Tikhonov-Phillips regularization. We then select a configuration, referred to as GEO-TIR, optimized for providing information in the lowermost troposphere (LmT; 0-3 km in height). For the GEO-TIR configuration we obtain around 1.5 degrees of freedom for O3 and 2 for CO at altitudes between 0 and 15 km. The error budget of GEO-TIR, calculated taking account of the principal contributions to the error (namely, temperature, measurement error, smoothing error) shows that information in the LmT can be achieved by GEO-TIR. We also retrieve analogous profiles from another geostationary infrared instrument with characteristics similar to the Meteosat Third Generation Infrared Sounder (MTG-IRS) which is dedicated to numerical weather prediction, referred to as GEO-TIR2. Comparison between GEO-TIR and GEO-TIR2 allows us to quantify the added value of GEO-TIR, a mission complementing the AQ observing system. To better characterize the information provided by GEO-TIR and GEO-TIR2 in the LmT, we retrieve two typical profiles of O3 and CO for different thermal contrast ranging from -10 K to 10 K. The shape of the first averaging kernel (corresponding to the surface level) confirms that GEO-TIR has good sensitivity to CO in the LmT and also to O3 for high positive thermal contrast. GEO-TIR2 has very low sensitivity in the LmT to O3 but can have sensitivity to CO with high positive thermal contrast. To quantify these results for a realistic atmosphere, we simulate it using the chemical transport model MOCAGE (MOdèle de Chimie Atmospherique à Grande Echelle) - this is the nature run. We simulate the O3 and CO spatial and temporal distributions from GEO-TIR observations in the LmT in July 2009 over Europe by sampling the nature run. Results show that GEO-TIR is able to capture well the spatial and temporal variability in the LmT for both O3 and CO, particularly during periods with high positive thermal contrast near the ground and high surface temperature, which results in active photochemistry and a raised planetary boundary layer. These results also provide evidence of the significant added value in the LmT of GEO-TIR compared to GEO-TIR2 by showing GEO-TIR is closer to the nature run than GEO-TIR2 for various statistical parameters (correlation, bias, standard deviation).
    Atmospheric Measurement Techniques Discussions. 07/2010; 3:3489-3534.
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    ABSTRACT: This paper presents an evaluation of a new linear parameterization valid for the troposphere and the stratosphere, based on a first order approximation of the carbon monoxide (CO) continuity equation. This linear scheme (hereinafter noted LINCO) has been implemented in the 3-D Chemical Transport Model (CTM) MOCAGE (MOdèle de Chimie Atmospherique Grande Echelle). First, a one and a half years of LINCO simulation has been compared to output obtained from a detailed chemical scheme output. The mean differences between both schemes are about ±25 ppbv (part per billion by volume) or 15% in the troposphere and ±10 ppbv or 100% in the stratosphere. Second, LINCO has been compared to diverse observations from satellite instruments covering the troposphere (Measurements Of Pollution In The Troposphere: MOPITT) and the stratosphere (Microwave Limb Sounder: MLS) and also from aircraft (Measurements of ozone and water vapour by Airbus in-service aircraft: MOZAIC programme) mostly flying in the upper troposphere and lower stratosphere (UTLS). In the troposphere, the LINCO seasonal variations as well as the vertical and horizontal distributions are quite close to MOPITT CO observations. However, a bias of ~-40 ppbv is observed at 700 Pa between LINCO and MOPITT. In the stratosphere, MLS and LINCO present similar large-scale patterns, except over the poles where the CO concentration is underestimated by the model. In the UTLS, LINCO presents small biases less than 2% compared to independent MOZAIC profiles. Third, we assimilated MOPITT CO using a variational 3D-FGAT (First Guess at Appropriate Time) method in conjunction with MOCAGE for a long run of one and a half years. The data assimilation greatly improves the vertical CO distribution in the troposphere from 700 to 350 hPa compared to independent MOZAIC profiles. At 146 hPa, the assimilated CO distribution is also improved compared to MLS observations by reducing the bias up to a factor of 2 in the tropics. This study confirms that the linear scheme is able to simulate reasonably well the CO distribution in the troposphere and in the lower stratosphere. Therefore, the low computing cost of the linear scheme opens new perspectives to make free runs and CO data assimilation runs at high resolution and over periods of several years.
    ATMOSPHERIC CHEMISTRY AND PHYSICS 06/2010; 10:6097-6115. · 5.51 Impact Factor

Publication Stats

3k Citations
193.62 Total Impact Points

Institutions

  • 1997–2011
    • National Center for Atmospheric Research
      • Division of Atmospheric Chemistry
      Boulder, CO, United States
  • 2002
    • National Research Center (CO, USA)
      Boulder, Colorado, United States