Analysis and interpretation of satellite measurements in the near-infrared spectral region with the focus on carbon monoxide

Carbon monoxide (CO) plays an important role in the Earth's atmosphere. Through its reaction with the hydroxyl radicals (OH) (Logan et al., 1981), CO affects the lifetime of atmospheric methane (CH4), and non-methane hydrocarbons (NMHCs). A main product of this oxidation is carbon dioxide (CO2). Therefore, containing no direct green-house potential, CO still has an indirect effect on the global warming. CO is also one of the most important health hazardous pollutants, which can cause diseases of different degrees of complexity. The nadir near-infrared measurements of scattered and reflected solar radiation by SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) instrument on board the ENVISAT satellite contain information about CO concentration in all atmospheric layers including the boundary layer, closest to the location of main CO sources. However, the retrieval of CO total column from the radiometric measurements in this spectral region is complicated as the CO overtone lines are weak, and overlapped by strong absorptions of water vapour and methane. Moreover, several known instrumental issues, like an ice layer on the detector and degradation of the detector pixels with time, additionally complicate the retrieval of CO vertical column from the of SCIAMACHY measurements in channel 8. In the scope of this work, the WFM-DOAS (Weighting Functions Modified Differential Optical Absorption Spectroscopy) retrieval algorithm, developed at the University of Bremen, have been improved in order to establish the retrieval of a multi-year CO dataset from SCIAMACHY nadir measurements. The modifications have led to an improved CO fit quality, i.e., to an overall much smaller fit residual. An error analysis and sensitivity studies based on the simulated measurements have shown that the error is generally less than 10%, which is comparable to the required precision for space-based CO measurements. However, due to high instrument noise, the error of the real measurements has been found to be much higher and considerably less stable. The retrieved CO columns have been validated by comparison with ground-based Fourier Transform Spectroscopy (FTS) measurements. A good agreement within 10-20% was found for nearly all considered stations. Furthermore, high correlation between the SCIAMACHY CO and CO from independent space-based total columns measurements performed by the MOPITT (Measurements of Pollution in the Troposphere) instrument onboard the Terra satellite indicates a good performance of the SCIAMACHY CO measurements globally. The overall difference of about 10% can be well explained by the moderate sensitivity of the thermal-infrared MOPITT measurements to lower atmospheric layers.Detailed analysis of the obtained CO dataset has been has been carried out on country level. Due to the presence of strong anthropogenic sources and prevailing west wind conditions, a positive difference of CO concentration is expected from the west to the east side of the United Kingdom. The analysis shows that SCIAMACHY is able to capture the positive 5% west-to-east CO gradient over the UK. These results are consistent with the direct airborne measurements during the AMPEP campaign, which estimated the CO concentration enhancement from the west to the east coast of the UK to be about 10-100 ppb, corresponding to the total column enhancement of 1-10% within the 1 km boundary layer. Over much stronger sources, such as a large biomass burning events, the quantitative potential of SCIAMACHY CO data is expected to be much higher due to much higher levels of CO signal and respectively more available ( good ) satellite measurements. To use this fact for further quantitative investigation, the SCIAMACHY simultaneously measurements of CO, nitrogen dioxide (NO2) and formaldehyde (HCHO) over biomass burning events in 2004, were analysed in the scope of the bottom-up emission estimation Excess Mixing Ratios (EMR) method. Good agreement has been found between the calculated SCIAMACHY (Delta CO)/(Delta HCHO) and (Delta CO)/(Delta NO2) and the ER values from referenced literature

Etude par modélisation et assimilation de données d'un capteur infrarouge géostationnaire pour la qualité de l'air

L'objectif de cette thèse porte sur la définition d'un capteur géostationnaire infrarouge pour l'observation de la composition chimique de la basse troposphère et l'évaluation de la valeur ajoutée de cet instrument afin de caractériser la variabilité de la moyenne et basse troposphère des principaux polluants et d'améliorer l'observation et les prévisions de la qualité de l'air. Nous nous sommes intéressés à deux polluants importants: l'ozone troposphérique en raison de son impact sur la santé humaine, les écosystèmes et le climat, et le monoxyde de carbone (CO) qui est un traceur de pollution nous renseignant sur les sources d'émissions et les processus de transport. Dans un premier temps, une évaluation d'un schéma linéaire pour la chimie du CO a été effectuée sur une période d'un an et demi en comparaison avec un schéma chimique détaillé (RACMOBUS) et différents types d'observations troposphériques et stratosphériques (satellitaires, aéroportées). L'intérêt principal de ce schéma est son faible coût en temps de calcul qui permet une assimilation sur de longues périodes de jeux de données de CO. L'assimilation de données MOPITT (Measurements Of Pollution In The Troposphere) dans ce schéma a d'ailleurs permis d'évaluer la valeur ajoutée de données d'observations infrarouges à l'échelle globale. Ensuite, les caractéristiques optimales du capteur géostationnaire infrarouge ont été définies en réalisant des études d'inversion de spectres atmosphériques pour sonder l'ozone et le CO pour la qualité de l'air, le but étant d'avoir un capteur techniquement et économiquement faisable, capable de sonder la basse troposphère. Le contenu en information de cet instrument a été comparé, en période estivale, à l'information apportée par un autre instrument infrarouge géostationnaire similaire à MTG-IRS (Meteosat Third Generation - Infrared Sounder), optimisé pour la mesure de la vapeur d'eau et de la température mais capable d'avoir une information sur la composition chimique de l'atmosphère. Enfin dans une dernière partie, la valeur ajoutée de ces deux instruments dans le modèle de qualité de l'air MOCAGE, a été quantifiée en utilisant des expériences de simulation de système d'observations sur une période de deux mois d'été (juillet - août 2009). La capacité de ces deux instruments à corriger différentes sources d'erreurs (les forçages atmosphériques, les émissions, l'état initial et les trois paramètres réunis) qui affectent les prévisions et simulations de qualité de l'air, a été quantifiées. Au final, l'instrument que nous avons défini s'avère effectivement capable d'apporter une contrainte efficace sur les champs d'ozone et de CO dans la moyenne et basse troposphère.The objective of this thesis is to define a geostationary infrared sensor to observe the atmospheric composition of the lowermost troposphere. We evaluate the potential added value of such an instrument at characterizing the variability of the main pollutants and improving air quality observations and forecasts. We focus on two air quality key pollutants: tropospheric ozone, because of its impact on human health, ecosystems and climate; carbon monoxide (CO), which is a tracer of pollutants emissions. Firstly, an evaluation of a linear scheme for the CO chemistry during one year and a half has been performed in comparison with a detailed chemical scheme (RACMOBUS) and different tropospheric and stratospheric observations (satellite and aircraft data). The advantage of such a scheme is its low computational cost which allows data assimilation of CO during long periods. Assimilation of CO data from the Measurements Of Pollution In The Troposphere (MOPITT) instrument allows us to evaluate the information brought by such infrared observations at the global scale. Secondly, the optimal configuration of a new infrared geostationary sensor has been defined using retrieval studies of atmospheric spectra with the objectives to contribute to the monitoring of ozone and CO for air quality purposes; our constraint also set the ground for a sensor with technically feasible and affordable characteristics. For reference, the information content of this instrument has been compared during summer to the information content from another infrared geostationary instrument similar to MTG-IRS (Meteosat Third Generation - Infrared Sounder), optimized to monitor water vapour and temperature but with monitoring atmospheric composition as Lastly, the potential added value of both instruments for air quality prognoses has been compared using observing system simulation experiments (OSSEs) over two summer months (July - August 2009). The skill of the two instruments to correct different error sources (atmospheric forcing, emission, initial state and the three conditions together) affecting air quality simulations and forecasts, has been characterised. In the end, it is concluded that the instrument configuration proposed is effectively able to bring a constraint on ozone and CO fields in the mid-to-low troposphere

An evaluation of a severe smog episode in the Eastern U.S. using regional modeling and satellite measurements

An ensemble of regional chemical modeling (WRF/Chem with RADM2) simulations, satellite, ozonesonde, and surface observations during July 7-11, 2007 was used to examine the horizontal and vertical signature of one of the worst smog events in the eastern U.S. in the past decade. The general features of this event -- a broad area of high pressure, weak winds and heavy pollution, terminated by the passage of a cold front -- were well simulated by the model. Average 8-hr maximum O3 has a mean (±Σ) bias of 0.59 (±11.0) ppbv and a root mean square error of 11.0 ppbv. WRF/Chem performed the best on poor air quality days, simulating correctly the spatial pattern of surface O3. Yet the model underpredicted O3 maxima by 5-7 ppbv in the Northeast and overpredicted by 8-11 ppbv in the Southeast. High O3 biases in the Southeast are explained by overpredicted temperatures in the model (>1.5°C). Sensitivity simulations with 1) accelerated O3 dry deposition velocity and 2) suppressed multiphase nitric acid formation pushed the model closer to observations. Simulated O3 vertical profiles over Beltsville, MD showed good agreement with ozonesonde measurements, but the modeled boundary layer depth was overpredicted on July 9, contributing to the low bias over this region. During this severe smog episode, space-borne TES detected high total tropospheric column ozone (TCO) over the Western Atlantic Ocean off the coast near North and South Carolina. The standard product (OMI/MLS) missed the magnitude of these local maxima, but the level-2 ozone profile (OMI) confirmed the TES observations. HYSPLIT back trajectories from these O3 maxima intersected regions of strong convection over the Southeast and Great Lakes regions. When lightning NO emissions were implemented in WRF/Chem, the high concentrations of NOx and O3 off the coast were well reproduced, showing that the exported O3 was produced by a combination of natural NO and pollutants lofted from the lower atmosphere. Lastly, WINTER MONEX O3 data from 1978 are presented for the first time here in discussion of open cell convection over Indonesia

The relevance of aerosol in the retrieval of tropospheric NO2 from satellite - a study of model data applicability

Nitrogen dioxide (NO2) is a key pollutant in the troposphere, being one of the main precursors of tropospheric ozone, and source of nitric acid, as well as contributing to global climate change. Tropospheric NO2 vertical columns can be determined from satellite observations, although some uncertainties are still associated with the retrieval process. The conversion from measured slant columns to vertical columns is accomplished with airmass factors (AMF) that are determined by radiative transfer (RT) models. While the measurement (instrumental) conditions are well assessed, improvement is still needed regarding the a priori information of atmospheric characteristics required for the estimation of AMFs (e.g., vertical distribution of the gas, aerosol loading and clouds). This thesis presents a sensitivity study focused on the impact of aerosol on the tropospheric NO2 AMF. Optical properties, size distribution, and vertical distribution of the aerosol were varied within several scenarios. Overall, the results show a tendency for two main opposite effects. On the one hand, enhancement of the measurement sensitivity occurs by means of multiple scattering, when aerosol is mixed with the trace gas. On the other hand, a shielding effect by an aerosol layer located above the NO2 is also verified. The identified pivotal factors for the AMF calculations were the relative vertical distribution of aerosol and NO2, the aerosol optical depth and the single scattering albedo, as well as the surface reflectance. A case study was developed, focusing on the impact on the NO2 measurements of volcanic ash emitted from Eyjafjallajökull during the spring of 2010. Aerosol and NO2 data from the EURAD chemical transport model (CTM) were used to design scenarios for the RT calculations. A small variation of AMFs was found, revealing that, in the days and region analysed, the satellite observations of NO2 were not significantly affected by the mentioned eruption. Nonetheless, it was verified that the conclusions of the study are dependent on the accuracy of the CTM data, and on the approach employed to account for (and determine) aerosol optical properties. Such findings highlight the potential challenges that can be faced in the future if model data are used in satellite retrievals. In addition, a model evaluation performed within the GEMS project is described, where global stratospheric and tropospheric NO2 columns predicted by two chemical transport models MOZART and TM5 are compared with SCIAMACHY observations. The evaluation exercise allowed for the identification of flaws in the model systems, showing problems with the prediction of high levels of pollution in some regions (e.g., East-Asia), and with the simulation of NO2 concentrations during biomass burning events

The relevance of aerosol in the retrieval of tropospheric NO2 from satellite - a study of model data applicability

Nitrogen dioxide (NO2) is a key pollutant in the troposphere, being one of the main precursors of tropospheric ozone, and source of nitric acid, as well as contributing to global climate change. Tropospheric NO2 vertical columns can be determined from satellite observations, although some uncertainties are still associated with the retrieval process. The conversion from measured slant columns to vertical columns is accomplished with airmass factors (AMF) that are determined by radiative transfer (RT) models. While the measurement (instrumental) conditions are well assessed, improvement is still needed regarding the a priori information of atmospheric characteristics required for the estimation of AMFs (e.g., vertical distribution of the gas, aerosol loading and clouds). This thesis presents a sensitivity study focused on the impact of aerosol on the tropospheric NO2 AMF. Optical properties, size distribution, and vertical distribution of the aerosol were varied within several scenarios. Overall, the results show a tendency for two main opposite effects. On the one hand, enhancement of the measurement sensitivity occurs by means of multiple scattering, when aerosol is mixed with the trace gas. On the other hand, a shielding effect by an aerosol layer located above the NO2 is also verified. The identified pivotal factors for the AMF calculations were the relative vertical distribution of aerosol and NO2, the aerosol optical depth and the single scattering albedo, as well as the surface reflectance. A case study was developed, focusing on the impact on the NO2 measurements of volcanic ash emitted from Eyjafjallajökull during the spring of 2010. Aerosol and NO2 data from the EURAD chemical transport model (CTM) were used to design scenarios for the RT calculations. A small variation of AMFs was found, revealing that, in the days and region analysed, the satellite observations of NO2 were not significantly affected by the mentioned eruption. Nonetheless, it was verified that the conclusions of the study are dependent on the accuracy of the CTM data, and on the approach employed to account for (and determine) aerosol optical properties. Such findings highlight the potential challenges that can be faced in the future if model data are used in satellite retrievals. In addition, a model evaluation performed within the GEMS project is described, where global stratospheric and tropospheric NO2 columns predicted by two chemical transport models MOZART and TM5 are compared with SCIAMACHY observations. The evaluation exercise allowed for the identification of flaws in the model systems, showing problems with the prediction of high levels of pollution in some regions (e.g., East-Asia), and with the simulation of NO2 concentrations during biomass burning events

Laboratory for Atmospheres 2008 Technical Highlights

The 2008 Technical Highlights describes the efforts of all members of the Laboratory for Atmospheres. Their dedication to advancing Earth Science through conducting research, developing and running models, designing instruments, managing projects, running field campaigns, and numerous other activities, is highlighted in this report. The Laboratory for Atmospheres (Code 613) is part of the Earth Sciences Division (Code 610), formerly the Earth Sun Exploration Division, under the Sciences and Exploration Directorate (Code 600) based at NASA s Goddard Space Flight Center in Greenbelt, Maryland. In line with NASA s Exploration Initiative, the Laboratory executes a comprehensive research and technology development program dedicated to advancing knowledge and understanding of the atmospheres of Earth and other planets. The research program is aimed at understanding the influence of solar variability on the Earth s climate; predicting the weather and climate of Earth; understanding the structure, dynamics, and radiative properties of precipitation, clouds, and aerosols; understanding atmospheric chemistry, especially the role of natural and anthropogenic trace species on the ozone balance in the stratosphere and the troposphere; and advancing our understanding of physical properties of Earth s atmosphere. The research program identifies problems and requirements for atmospheric observations via satellite missions. Laboratory scientists conceive, design, develop, and implement ultraviolet, infrared, optical, radar, laser, and lidar technology for remote sensing of the atmosphere. Laboratory members conduct field measurements for satellite data calibration and validation, and carry out numerous modeling activities. These modeling activities include climate model simulations, modeling the chemistry and transport of trace species on regional-to-global scales, cloud-resolving models, and development of next-generation Earth system models. Interdisciplinary research is carried out in collaboration with other laboratories and research groups within the Earth Sciences Division, across the Sciences and Exploration Directorate, and with partners in universities and other Government agencies. The Laboratory for Atmospheres is a vital participant in NASA s research agenda. Our Laboratory often has relatively large programs, sizable satellite missions, and observational campaigns that require the cooperative and collaborative efforts of many scientists. We ensure an appropriate balance between our scientists responsibility for these large collaborative projects and their need for an active individual research agenda. This balance allows members of the Laboratory to continuously improve their scientific credentials. Members of the Laboratory interact with the general public to support a wide range of interests in the atmospheric sciences. Among other activities, the Laboratory raises the public s awareness of atmospheric science by presenting public lectures and demonstrations, by making scientific data available to wide audiences, by teaching, and by mentoring students and teachers. The Laboratory makes substantial efforts to attract new scientists to the various areas of atmospheric research. We strongly encourage the establishment of partnerships with Federal and state agencies that have operational responsibilities to promote the societal application of our science products. This report describes our role in NASA s mission, gives a broad description of our research, and summarizes our scientists major accomplishments during calendar year 2008. The report also contains useful information on human resources, scientific interactions, and outreach activities

Global and regional trends of Aerosol Optical Thickness derived using satellite- and ground-based observations

Atmospheric aerosol plays a critical role for human health, air quality, long range transport of pollution, and the Earth s radiative balance, thereby influencing global climate change. To test our scientific understanding and provide an evidence base for policymakers, long-term temporal changes of local, regional, and global aerosols are needed. Remote sensing from satellite borne and ground based observations offers unique opportunities to provide such data. However, only a few studies have discussed the limitations, associated with unrepresentative sampling originating from large/persistent cloud disturbance and limited/different sampling (limited orbital periods and different sampling times) in the trend analysis. Using a linear weighted model, the long-term trends of global AOTs from various polar orbiting satellites and ground observations: MODIS (aboard Terra), MISR (Terra), SeaWiFS (OrbView-2), MODIS (Aqua), and AERONET have been analyzed. In this manner, the present study attempts to minimize the influence of unrepresentative sampling in the trend analysis. Throughout terrestrial and marine regions, temporal increase of cloud-free AOTs were dominat over the globe (GL), northern (NH), and southern hemisphere (SH) (up to 0.00348±0.00185 for GL, 0.00514±0.00272 for NH, and 0.00232±0.00124 per year for SH). Generally, consistently in all observations, the weighted trends over Eastern US and OECD Europe showed a strong decreasing AOT (up to -0.00376±0.00174 for Eastern US and -0.00530±0.00304 per year for OECD Europe) attributed to the recent environmental legislation and resulting regulation of emissions. A significant increase was observed over Saharan/Arabian deserts, South, and East Asia (up to 0.00618±0.00326, 0.01452±0.00615, and 0.01939±0.00986 per year, respectively). These in part dramatic increases are caused by the enhanced amount of aerosol transported/emitted from industrialization, urbanization, deforestation, desertification, and climate change. Overall large/persistent cloud disturbance all year round and the limited/different sampling of polar orbiting satellites represent a challenge, which has been addressed successfully in this study for the accurate determination of aerosol amount and its trends

Effets direct et semi-direct des aérosols en Afrique de l'ouest pendant la saison sèche

Ces travaux de thèse présentent l'étude du forçage radiatif direct et semi-direct ainsi que les impacts climatiques associés, qu'exercent les particules d'aérosols désertiques et de feux de biomasse sur le climat régional ouest Africain pendant la saison sèche. Dans ce cadre, le modèle de climat à été utilisé en lien avec les observations in-situ des campagnes DABEX/AMMA-SOP0, les mesures photométriques (AERONET/PHOTONS) et satellitaire (PARASOL,MODIS,OMIetMISR). Le modèle RegCM3 configuré spécifiquement pour représenter les aérosols d'Afrique de l'ouest a été évalué au cours d'une simulation de la saison sèche 2006. Dans cette configuration, le modèle s'est montré capable d'estimer raisonnablement les quantités d'aérosols pour des applications climatiques et les variations d'albédo de simple diffusion. Pendant les mois de décembre et janvier, l'albédo de simple diffusion simulé au dessus du Sahel se situe entre 0.81 et 0.83 (à 440 nm) quand les aérosols de feux de biomasse dominent le mélange atmosphérique. Pendant les mois de mars et avril, pour lesquels les aérosols désertiques dominent, l'albédo de simple diffusion simulé se situe entre 0.90 et 0.92 (à 440 nm). Le forçage radiatif direct au sommet de l'atmosphère (visible + infrarouge) est majoritairement négatif sur l'ensemble du domaine et compris entre -5.0 W /m2 et -4.0 W /m2. Sur le Sahara, le forçage radiatif direct TOA est proche de zéro (-0.15 W /m2). La grande divergence entre le forçage radiatif direct au sommet de l'atmosphère et en surface indique que l'absorption est importante au sein de l'atmosphère (forçage radiatif direct atmosphèrique de +11.47 et +24.40 W /m2 au dessus du Sahara et du Sahel, respectivement). Du fait de leur albédo de simple diffusion relativement bas, les aérosols de feux de biomasse, contribuent principalement à ce rechauffement atmosphérique. Ceci se traduit à l'échelle régionale par un taux d'échauffement radiatif atmosphérique (dans le visible) compris entre +0.2 et +0.6 K /jour en moyenne journalière dans la couche d'aérosol de feux de biomasse localisée entre 2 et 5 km. Deux simulations à plus longue échéance sur la période 2001-2006 ont été menées pour étudier les conséquences de ce forçage radiatif sur le climat régional pendant la saison sèche. Une simulation DUST (aérosols désertiques) et BBDUST (aérosols désertiques + aérosols de feux) sont réalisées en prenant en compte les rétroactions liées au forçage radiatif direct. L'important forçage radiatif en surface réduit l'énergie radiative disponible au sol. Ceci conduit à des perturbations significatives du bilan energétique en surface. Au dessus du Sahara, les réductions de flux de chaleur sensible sont proches dans les expériences DUST et BBDUST (respectivement -5.52 W /m2 et -6.65 W /m2). Au niveau du Sahel en revanche, l'inclusion des aérosols de feux de biomasse diminue plus fortement le flux de chaleur sensible (-16.59 W /m2 dans l'expérience BBDUST et -5.37 W /m2 dans l'expérience DUST). La réponse du flux de chaleur latente est plus complexe et dépend à la fois de la localisation des sources d'aérosols et des espèces considérées. Ainsi, la réponse des champs de précipitations simulés due aux effets radiatifs direct et semi-direct des aérosols diffère fortement entre les deux expériences. Dans l'expérience DUST, les précipitations sont réduites sur la majorité du domaine avec une diminution maximum au centre du continent. Dans l'expérience BBDUST, les aérosols de feux de biomasse augmentent les précipitations pour cette sous-région. L'augmentation des précipitations semble reliée à une augmentation locale de l'activité convective au dessus de 500 hPa sous l'effet d'un mécanisme de pompe thermique.This work investigates direct and semi-direct aerosol radiative forcing and the associated climatic impacts over the West African region during the dry-season. The regional climate model version 3 (RegCM3) is used in combination with in-situ observations from the AMMA­SOP0/DABEX field campaigns and remote sensing observations from sunphotometry (AE­RONET/PHOTON) and satellite platforms (PARASOL, MODIS, OMI and MISR). RegCM3 is specifically configured to represent West African aerosols and is evaluated for the 2006 dry season. In this setup, RegCM3 is found to represent aerosol loadings accurately enough for climatic applications, with the model simulating consistent aerosol single scattering albedo variations. In december and January, when smoke aerosols dominate the background aerosol loading, the aerosol single scattering albedo over the Sahel ranges from 0.81 0.83 (at 440 nm). During the months of march and april, when dust aerosol are mainly observed, the simu­lated aerosol single scattering albedo ranges between 0.90 and 0.92 (at 440 nm). The direct aerosol radiative forcing (visible + infrared) estimated at top of the atmosphere is essentially negative over the whole domain, with values ranging from -5 W /m2 to -4.0 W /m2. Over the Sahara, the direct aerosol radiative forcing at top of the atmosphere (TOA) is close to zero (-0.15 W /m2). The large difference between the TOA and surface direct radiative forcing in­dicates strong radiative absorption in the atmosphere (+11.47 and +24.40 W /m2 over the Sahara and Sahel, respectively). Due to their relatively low single scattering albedo, smoke aerosols are the dominant contributors to atmospheric heating. At the regional scale, this results in a daily average atmospheric heating rates ranging between +0.2 and +0.6 K /day within the main smoke layers (approximately 2 and 5 km above the ground surface). Two lon­ger simulations covering the 2001-2006 period are also conducted in order to investigate the effects of this radiative forcing on the regional climate during the dry season. A simulation including dust aerosols (DUSTexp) and a simulation including both dust and smoke aerosols (BBDUSTexp) are performed in order to take into account the dynamical feedbacks associa­ted with direct and semi-direct aerosol radiative forcing. The strong aerosol radiative forcing at surface decreases available radiation, which leads to significant perturbations of the sur­face energy balance. Over the Sahara, sensible heat flux anomalies are similar in the two experiments (-5.52 W /m2 and -6.65 W /m2, in the DUSTexp and BBDUSTexp, respectively). Over the Sahel, the decrease is more significant in BBDUSTexp simulation (-16.59 W /m2 compared to -5.37 W /m2 in DUSTexp). Changes in latent heat fluxes are more complex and depend simultaneously on aerosols emission locations and the aerosol species present. As a result, the precipitation changes due to aerosol radiative effects are very different within the two experiments. In the DUSTexp, precipitation is decreased over most of the domain with a maximum decrease over the central part of the continent. For the BBDUSTexp, smoke aero­sols tend to enhance precipitation over this sub-region. This increase seems to be related to a local increase of convective activity above 500 hPa, resulting from an elevated heat pump mechanism

A Greenhouse-Gas Information System: Monitoring and Validating Emissions Reporting and Mitigation

This study and report focus on attributes of a greenhouse-gas information system (GHGIS) needed to support MRV&V needs. These needs set the function of such a system apart from scientific/research monitoring of GHGs and carbon-cycle systems, and include (not exclusively): the need for a GHGIS that is operational, as required for decision-support; the need for a system that meets specifications derived from imposed requirements; the need for rigorous calibration, verification, and validation (CV&V) standards, processes, and records for all measurement and modeling/data-inversion data; the need to develop and adopt an uncertainty-quantification (UQ) regimen for all measurement and modeling data; and the requirement that GHGIS products can be subjected to third-party questioning and scientific scrutiny. This report examines and assesses presently available capabilities that could contribute to a future GHGIS. These capabilities include sensors and measurement technologies; data analysis and data uncertainty quantification (UQ) practices and methods; and model-based data-inversion practices, methods, and their associated UQ. The report further examines the need for traceable calibration, verification, and validation processes and attached metadata; differences between present science-/research-oriented needs and those that would be required for an operational GHGIS; the development, operation, and maintenance of a GHGIS missions-operations center (GMOC); and the complex systems engineering and integration that would be required to develop, operate, and evolve a future GHGIS