Modélisation du trafic routier pour l’étude de la pollution atmosphérique de proximité : représentation des flux grâce aux données de comptages routiers

National audience

Timing and patterns of the ENSO signal in Africa over the last 30 years: insights from normalized difference vegetation index data.

Abstract A more complete picture of the timing and patterns of the ENSO signal during the seasonal cycle for the whole of Africa over the three last decades is provided using the normalized difference vegetation index (NDVI). Indeed, NDVI has a higher spatial resolution and is more frequently updated than in situ climate databases, and highlights the impact of ENSO on vegetation dynamics as a combined result of ENSO on rainfall, solar radiation, and temperature. The month-by-month NDVI–Niño-3.4 correlation patterns evolve as follows. From July to September, negative correlations are observed over the Sahel, the Gulf of Guinea coast, and regions from the northern Democratic Republic of Congo…

Marrakair: une simulation participative pour observer les émissions atmosphériques du trafic routier en milieu urbain

National audience; D’après l’Organisation Mondiale de la Santé (OMS), la pollution de l’air est le principal risque environnemental pour la santé dans le monde 1 (OMS, 2013). Àl’échelle locale, la pollution atmosphérique agit sur quelques kilomètres et se manifeste à proximité des sources de pollution comme la proximité aux sites industriels. En milieu urbain, le premier contributeur aux émissions de NOx, CO, ou PM10 dans l’atmosphère est le trafic routier (CITEPA, 2014). La pollution atmosphérique automobile (PAA) se caractérise en effet par l’émission de composés toxiques et cancérigènes directement émis par les moteurs. L’intensité des émissions est à relier au nombre de véhicules présen…

Radiometric calibration of SeaWIFS in the near infrared

The radiometric calibration of the Sea-Viewing Wide-Field-of-View Sensor (SeaWiFS) in the near infrared (band 8, centered on 865 nm) is evaluated by use of ground-based radiometer measurements of solar extinction and sky radiance in the Sun's principal plane at two sites, one located 13 km off Venice, Italy, and the other on the west coast of Lanai Island, Hawaii. The aerosol optical thickness determined from solar extinction is used in an iterative scheme to retrieve the pseudo aerosol phase function, i.e., the product of single-scattering albedo and phase function, in which sky radiance is corrected for multiple scattering effects. No assumption about the aerosol model is required. The ae…

De Mustard à Qaémléo : la construction d’un observatoire environnemental participatif

International audience; Depuis 2017, Dijon Métropole développe un projet de ville intelligente pour améliorer la gestion urbaine au quotidien. Ce nouveau récit métropolitain s’inscrit également dans une approche originale pour garantir un accès sécurisé aux données produites par la ville intelligente. Parallèlement à cette action, les chercheurs du campus dijonnais se sont engagés, dans le cadre du programme POPSU, à constituer un observatoire intelligent pour la qualité environnementale selon les principes FAIR : Facile à trouver, Accessible, Interopérable, Réutilisable. Se pose alors la question de comment faire converger ces infrastructures smart pour FAIR.E métropole ?

La Qualité de l’air en ville à Très haute Résolution (Quali_ThR): Apport des images Pléiades dans la démarche SCAUP ?

International audience

Towards understanding the epidemiology of Neisseria meningitidis in the African meningitis belt: a multi-disciplinary overview

International audience; Objectives: Neisseria meningitidis is the major cause of seasonal meningitis epidemics in the African meningitis belt. In the changing context of a reduction in incidence of serogroup A and an increase in incidence of serogroups W and C and of Streptococcus pneumoniae, a better understanding of the determinants driving the disease transmission dynamics remains crucial to improving bacterial meningitis control.Methods: The literature was searched to provide a multi-disciplinary overview of the determinants of meningitis transmission dynamics in the African meningitis belt.Results: Seasonal hyperendemicity is likely predominantly caused by increased invasion rates, spo…

L’apport de la simulation multi-agent du trafic routier pour l’estimation des pollutions atmosphériques automobiles

National audience; La pollution atmosphérique est aujourd’hui considérée comme cancérigène pour la santé humaine (OMS, 2013). Avec le bruit, elle est l’une des premières nuisances directement ressenties par les populations en milieu urbain. Son évaluation présente un véritable enjeu pour les pouvoirs publics afin de mieux en identifier ses sources, ses impacts en vue de définir des politiques territoriales (PDU, cadastre d’émission). A l’échelle locale, la pollution atmosphérique est à relier directement à l’intensité des sources d’émissions qui vont accentuer, ou non, la qualité de l’air extérieure (Elichegaray, 2010) . En milieu urbain, le premier contributeur en émission de NOx, CO, ou P…

Utilisation d'ensembles de simulations climatiques sur Modèles de Circulation Générale de l'Atmosphère: concepts, méthodes et applications à la climatologie de l'espace Sud-Africain,

International audience

Vicarious calibration of MERIS over dark waters in the near infrared

Abstract We propose to evaluate the calibration of MERIS (MEdium Resolution Imaging Spectrometer) over dark waters in the near infrared. We work with 5 months of data, from July to November 2003, over five world sites: Venice and Lampedusa in Italy, El Arenosillo in Spain, MOBY/Lanai and CalCOFI/San Nicolas in the United States. The sites are all equipped with a CIMEL station that forms part of the AERONET network. The basic idea is to associate CIMEL sky radiance measurements with MERIS level-1b data in a twin geometry which corresponds to the same scattering angle. This vicarious calibration relies on an accurate description of the atmospheric scattering based on the CIMEL measurements. A…

Downscaling West African climate : uncertainties, sensitivity to the model physics and regional variability

We present here a set of regional climate simulations, complementary to the CORDEX-Africa modeling exercice, performed over West Africa during the 1989-2010 period using the non-hydrostatic model WRF. Lateral and SST forcings are provided by ERA-Interim reanalyses. The regional domain [45W 45E 10S 30N] encompasses West Africa and the nearby Atlantic Ocean and Gulf of Guinea. The grid resolution is moderate (80km, with 28 levels on the vertical) in order to reduce computational costs and multiply sensitivity experiments. A first set of fifteen 20-year long simulations addresses the influence of the model physics (convective, radiative and land surface schemes). A second set of simulations co…

Impacts d’une meilleure description de la végétation urbaine sur des simulations du climat urbain avec SURFEX-TEB.

Le réseau MUSTARDijon offre la possibilité de procéder à une cartographie fine des températureshoraires sur Dijon Métropole. La méthode proposée ici repose sur des régressions linéaires multiplesmobilisant deux familles de prédicteurs : des descripteurs du relief et des descripteurs de l’occupation dusol. L’application porte sur la canicule de l’été 2020 (6-9 août). Deux configurations sont comparées. L’une,en mode recherche, laisse la possibilité aux descripteurs de varier dynamiquement en fonction de leurpertinence statistique, l’autre, en mode opérationnel, impose les 5 mêmes descripteurs en entrée. Entermes de performance statistique ou de structure spatiale, l’impact de la méthode n’es…

Interannual memory effects for spring NDVI in semi-arid South Africa

[1] Almost 20 years of Normalized Difference Vegetative Index (NDVI) and precipitation (PPT) data are analysed to better understand the interannual memory effects on vegetation dynamics observed at regional scales in Southern Africa (SA). The study focuses on a semi-arid region (25°S–31°S; 21°E–26°E) during the austral early summer (September–December). The memory effects are examined using simple statistical approaches (linear correlations and regressions) which require the definition of an early summer vegetation predictand (December NDVI minus September NDVI) and a consistent set of potential predictors (rainfall amount, number of rainy days, rainfall intensity, NDVI and Rain-Use-Efficie…

Impact des précipitations sur l'activité photosynthétique de la végétation en Afrique semi-aride sub-saharienne

National audience

État actuel des réseaux de mesures éco-climatiques en Afrique centrale : les ambitions du projet de recherche international FORGREENE.

This work presents an overview of spatio-temporal quality andspatial density of rainfall networks of Cameroon, Gabon, Congo, CAP and DRC, particularly in the recentperiod (1973-2014) through the GSOD international database. Faced with enormous gaps observed, theseresults will help to select metrological and analytical orientations in FORGREENE project (Tropical forestsgreeness and cloudiness in Central Africa: present conditions and future evolution). A comparison with rainfallsatellite estimates (RFE type) also indicates their great potential, provided they are based on in situ validations.

Analysis of the relationships between climate/aerosols and meningitis epidemics in Western Africa

Analysis of cloudiness and solar radiation diurnal cycles for a better understanding of the forests greenness mean annual cycle in Central Africa.

To better understand the Central Africa forests sensitivity toclimate variability, we jointly analyse the mean annual cycles of greenness, rainfall, cloudiness and solarradiation for the target region 0-5°N/12-19°E using high resolution satellite data. Our results demonstrate theimportance of the diurnal scale for understanding the mean annual cycles of rainfall, cloudiness and solarradiation and the way they shape those of forest greenness. They also suggest that whereas the March-Mayrainy season appears optimal for greenness especially because of favorable light conditions, water availabilityis the main controlling factor in December-January the main dry season and in February at the star…

Suitability of OMI aerosol index to reflect mineral dust surface conditions: preliminary application for studying the link with meningitis epidemics in the Sahel.

12 pages; International audience; The aimof this study is to analyze the suitability of remotely-sensed aerosol retrievals to progress in the understanding of the influence of desert dust on health, and particularly on meningitis epidemics. In the Sahel, meningitis epidemics are a serious public health issue. Social factors are of prime importance in the dynamics of the epidemics, however climate and environmental factors are also suspected to play an important role. This study focuses on three Sahelian countries (Burkina Faso,Mali and Niger) which are among the most concerned in the "meningitis belt" and affected by strong dust events every year. It investigates the capability of the aeros…

Caractérisation de la variabilité inter et intra-annuelle du NDVI en Afrique de l'ouest sur la période 1982-2002 à l'aide des données NOAA-AVHRR.

28 novembre-2 décembre 2005; International audience

Définition d’un événement de poussières désertiques au Sahel : apport de nouvelles mesures de PM10 au Burkina Faso.

This study isdedicated to the desert dust of the dry season in an inhabited Sahelian rural area whose populations are widely exposed tosanitary risks such as meningitis outbreaks (Martiny & Chiapello, 2013). Here, the objective is to give a definition of a dust“event”, a concept describing the dustiest moments in a dusty environment, but that remains rather unclear, notably becauseof the lack of ground-truth measurements. The analysis of new PM10 measurements in Burkina Faso has enabled us to definethe dust events as episodes which experience concentrations greater than 189μg/m3 for at least 10h. Five types of dust eventshave been defined depending on the concentrations measured. On the fir…

La démarche de modélisation SCAUP : Simulation multi-agents à partir de CApteurs Urbains pour la Pollution atmosphérique automobile.

Determinants of the interannual relationships between remote sensed photosynthetic activity and rainfall in tropical Africa

International audience; The response of photosynthetic activity to interannual rainfall variations in Africa South of the Sahara is examined using 20 years (1981-2000) of Normalised Difference Vegetation Index (NDVI) AVHRR data. Linear correlations and regressions were computed between annual NDVI and annual rainfall at a 0.5° latitude/longitude resolution, based on two gridded precipitation datasets (Climate Prediction Center Merged Analysis of Precipitation [CMAP] and Climatic Research Unit [CRU]). The spatial patterns were then examined to detect how they relate to the mean annual rainfall amounts, land-cover types as from the Global Land Cover 2000 data set, soil properties and soil typ…

Du comptage ponctuel à l'affectation par simulation multi-agents : application à la circulation routière de la ville de Dijon

A travers une démarche expérimentale de simulation de la circulation routière pour estimer les pollutions atmosphériques en milieu urbain, cette proposition questionne les opportunités qu'offre la simulation multi-agents pour intégrer des données d'observations du trafic routier au sein d'un système d'information géographique. Pour cela, la construction du modèle d'affectation s'est faite en deux étapes : une première, d'acquisition et de structuration des données de comptages et une seconde visant à interfacer ces données au sein d'une plateforme de simulation multi-agents pour en reproduire la variabilité intra journalière et la fréquentation routière.

Comment et pour qui cartographier l’îlot de chaleur urbain (ICU) ?

Le réseau MUSTARDijon offre la possibilité de procéder à une cartographie fine des températureshoraires sur Dijon Métropole. La méthode proposée ici repose sur des régressions linéaires multiplesmobilisant deux familles de prédicteurs : des descripteurs du relief et des descripteurs de l’occupation dusol. L’application porte sur la canicule de l’été 2020 (6-9 août). Deux configurations sont comparées. L’une,en mode recherche, laisse la possibilité aux descripteurs de varier dynamiquement en fonction de leurpertinence statistique, l’autre, en mode opérationnel, impose les 5 mêmes descripteurs en entrée. Entermes de performance statistique ou de structure spatiale, l’impact de la méthode n’es…

An agent-based model of a cutaneous leishmaniasis reservoir host, Meriones shawi

International audience; Meriones shawi (M.shawi) is the main reservoir host for zoonotic cutaneous leishmaniasis (ZCL) in Central Tunisia. The incorporation of environmental and climatic effects on the spread of ZCL in M. shawi remains difficult. This study presents an agent-based model (ABM) to overcome these difficulties and examine the impact of environment (i.e. vegetation cover) and climate (i.e. temperature) on M. shawi movement and prevalence. The model simulation considers two agent types: rodent agent and field unit agent. We tested the model according to two types of rodent movement: random and thoughtful. We integrated time dependent normalized difference vegetation index (NDVI) …

Characterization of the interannual and intraseasonal variability of West African vegetation between 1982 and 2002 by means of NOAA AVHRR NDVI data

AbstractThe interannual and intraseasonal variability of West African vegetation over the period 1982–2002 is studied using the normalized difference vegetation index (NDVI) from the Advanced Very High Resolution Radiometer (AVHRR).The novel independent component analysis (ICA) technique is applied to extract the main modes of the interannual variability of the vegetation, among which two modes are worth describing. The first component (IC1) describes NDVI variability over the Sahel from August to October. A strong photosynthetic activity over the Sahel is related to above-normal convection and rainfall within the intertropical convergence zone (ITCZ) in summertime and is partly associated …

Exploitation of traffic counting data for traffic study in urban areas: from traffic assignment to simulation model validation

International audience

Advances in the analyses of dust/climate and meningitis relationships based on a multidisciplinary approach

International audience

Relationships between dust aerosols and meningitis epidemics using satellite data sets

Compared regimes of NDVI and rainfall in semi‐arid regions of Africa

Bi‐monthly normalized difference vegetation index (NDVI) at an 8 km spatial resolution from the advanced very high resolution radiometers (AVHRR) was used from 1981 to 1995 to analyse the vegetation response to rainfall supply in semi‐arid regions of Africa. Within the 200–600 mm annual rainfall belt, for which the apparent NDVI response to rainfall was the strongest, three regions were selected which exhibited different patterns in their NDVI regimes and/or relationships with rainfall. The regions, located in western, southern and eastern Africa, were split into coherent sub‐regions in terms of mean regime of photosynthetic activity through a cluster analysis. Overall, intra‐regional diffe…

"About the potential role of dust aerosols on the meningitis disease in Western Africa”

International audience

Atmospheric dust, early cases, and localized meningitis epidemics in the African meningitis belt: an analysis using high spatial resolution data.

8 pages; International audience; Background : Bacterial meningitis causes a high burden of disease in the African meningitis belt, with regular seasonal hyperendemicity and sporadic short, but intense, localized epidemics during the late dry season occurring at a small spatial scale [i.e., below the district level, in individual health centers (HCs)]. In addition, epidemic waves with larger geographic extent occur every 7–10 y. Although atmospheric dust load is thought to be an essential factor for hyperendemicity, its role for localized epidemics remains hypothetic.Objectives : Our goal was to evaluate the association of localized meningitis epidemics in HC catchment areas with the dust lo…

Interannual persistence effects in vegetation dynamics of semi-arid Africa

[1] Over 15 years of Normalized Difference Vegetation Index (NDVI) data from the Advanced Very High Resolution Radiometers (AVHRR) are used to study the response of vegetation activity to rainfall in three semi-arid regions of Africa. The relationships between annual NDVI and annual precipitation (PPT) time series are examined using statistical approaches (simple and partial correlations, linear multiple regressions). It appears that annual NDVI highly depends on PPT of the concurrent year and the previous year. An analysis of particularly dry and wet years enables to better diagnose two distinct responses of vegetation activity to rainfall. The “recovery” effect represents the difficulty o…

About the potential role of desert dust in the West African meningitis epidemics

The association between respiratory tract infection incidence and localised meningitis epidemics: an analysis of high-resolution surveillance data from Burkina Faso.

AbstractMeningococcal meningitis epidemics in the African meningitis belt consist of localised meningitis epidemics (LME) that reach attack proportions of 1% within a few weeks. A meningococcal serogroup A conjugate vaccine was introduced in meningitis belt countries from 2010 on, but LME due to other serogroups continue to occur. The mechanisms underlying LME are poorly understood, but an association with respiratory pathogens has been hypothesised. We analysed national routine surveillance data in high spatial resolution (health centre level) from 13 districts in Burkina Faso, 2004–2014. We defined LME as a weekly incidence rate of suspected meningitis ≥75 per 100,000 during ≥2 weeks; and…

Assessments for the impact of mineral dust on the meningitis incidence in West Africa.

9 pages; International audience; Recently, mineral dust has been suspected to be one of the important environmental risk factor for meningitis epidemics in West Africa. The current study is one of the first which relies on long-term robust aerosol measurements in the Sahel region to investigate the possible impact of mineral dust on meningitis cases (incidence). Sunphotometer measurements, which allow to derive aerosol and humidity parameters, i.e., aerosol optical thickness, Angström coefficient, and precipitable water, are combined with quantitative epidemiological data in Niger and Mali over the 2004-2009 AMMA (African Monsoon Multidisciplinary Analysis) program period. We analyse how th…

The ADCEM project : Impacts of dust/climate on meningitis in the Sahel

Chapitre 3. Caractériser la morphologie urbaine via un SIG pour la simulation numérique du climat urbain.

44 pages; National audience

Predictability of NDVI in semi-arid West, East and South Africa