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Accurate simulation of the spatial and temporal variability of tracer mixing ratios over urban areas is a challenging and interesting task needed to be performed in order to utilise CO² measurements in an atmospheric inverse framework and to better estimate regional CO² fluxes. This study investigates the ability of a high-resolution model to simulate meteorological and CO² fields around Paris agglomeration during the March field campaign of the CO²- MEGAPARIS project. The mesoscale atmospheric model Meso-NH, running at 2 km horizontal resolution, is coupled with the Town Energy Balance (TEB) urban canopy scheme and with the Interactions between Soil, Biosphere and Atmosphere CO²-reactive (ISBA-A-gs) surface scheme, allowing a full interaction of CO² modelling between the surface and the atmosphere. Statistical scores show a good representation of the urban heat island (UHI) with stronger urban-rural contrasts on temperature at night than during the day by up to 7°C. Boundary layer heights (BLH) have been evaluated on urban, suburban and rural sites during the campaign, and also on a suburban site over 1 yr. The diurnal cycles of the BLH are well captured, especially the onset time of the BLH increase and its growth rate in the morning, which are essential for tall tower CO² observatories. The main discrepancy is a small negative bias over urban and suburban sites during nighttime (respectively 45m and 5 m), leading to a few overestimations of nocturnal CO² mixing ratios at suburban sites and a bias of +5 ppm. The diurnal CO² cycle is generally well captured for all the sites. At the Eiffel tower, the observed spikes of CO² maxima occur every morning exactly at the time at which the atmospheric boundary layer (ABL) growth reaches the measurement height. At suburban ground stations, CO² measurements exhibit maxima at the beginning and at the end of each night, when the ABL is fully contracted, with a strong spatio-temporal variability. A sensitivity test without urban parameterisation removes the UHI and underpredicts nighttime BLH over urban and suburban sites, leading to large overestimation of nocturnal CO² mixing ratio at the suburban sites (bias of +17 ppm). The agreement between observation and prediction for BLH and CO² concentrations and urban-rural increments, both day and night, demonstrates the potential of using the urban mesoscale system in the context of inverse modelling. [ABSTRACT FROM AUTHOR]

Accurate simulation of the spatial and temporal variability of tracer mixing ratios over urban areas is challenging, but essential in order to utilize CO2 measurements in an atmospheric inverse framework to better estimate regional CO2 fluxes. This study investigates the ability of a high-resolution model to simulate meteorological and CO2 fields around Paris agglomeration, during the March field campaign of the CO2-MEGAPARIS project. The mesoscale atmospheric model Meso-NH, running at 2 km horizontal resolution, is coupled with the Town-Energy Balance (TEB) urban canopy scheme and with the Interactions between Soil, Biosphere and Atmosphere CO2-reactive (ISBA-A-gs) surface scheme, allowing a full interaction of CO2 between the surface and the atmosphere. Statistical scores show a good representation of the Urban Heat Island (UHI) and urban-rural contrasts. Boundary layer heights (BLH) at urban, sub-urban and rural sites are well captured, especially the onset time of the BLH increase and its growth rate in the morning, that are essential for tall tower CO2 observatories. Only nocturnal BLH at sub-urban sites are slightly underestimated a few nights, with a bias less than 50m. At Eiffel tower, the observed spikes of CO2 maxima occur every morning exactly at the time at which the Atmospheric Boundary Layer (ABL) growth reaches the measurement height. The timing of the CO2 cycle is well captured by the model, with only small biases on CO2 concentrations, mainly linked to the misrepresentation of anthropogenic emissions, as the Eiffel site is at the heart of traffic emission sources. At suburban ground stations, CO2 measurements exhibit maxima at the beginning and at the end of each night, when the ABL is fully contracted, with a very strong spatio-emporal variability. The CO2 cycle at these sites is generally well reproduced by the model, even if some biases on the nocturnal maxima appear in the Paris plume parly due to small errors on the vertical transport, or in the vicinity of airports due to small errors on the horizontal transport (wind direction). A sensitivity test without urban parameterisation removes UHI and underpredicts nighttime BLH over urban and sub-urban sites, leading to large overestimation of nocturnal CO2 concentration at the sub-urban sites. The agreement of daytime and nighttime BLH and CO2 predictions of the reference simulation over Paris agglomeration demonstrates the potential of using the meso-scale system on urban and sub-urban area in the context of inverse modelling. [ABSTRACT FROM AUTHOR]

In order to evaluate the uncertainty associated with the impact model in climate change studies, a CO2 responsive version of the land surface model ISBA (ISBA-A-gs) is compared with its standard version in a climate impact assessment study. The study is performed over the French Mediterranean basin using the Safran-Isba-Modcou chain. A downscaled A2 regional climate scenario is used to force both versions of ISBA, and the results of the two land surface models are compared for the present climate and for that at the end of the century. Reasonable agreement is found between models and with discharge observations. However, ISBA-A-gs has a lower mean evapotranspiration and a higher discharge than ISBA-Standard. Results for the impact of climate change are coherent on a yearly basis for evapotranspiration, total runoff, and discharge. However, the two versions of ISBA present contrasting seasonal variations. ISBA-A-gs develops a different vegetation cycle. The growth of the vegetation begins earlier and reaches a slightly lower maximum than in the present climate. This maximum is followed by a rapid decrease in summertime. In consequence, the springtime evapotranspiration is significantly increased when compared to ISBA-Standard, while the autumn evapotranspiration is lower. On average, discharge changes are more significant at the regional scale with ISBA-A-gs. [ABSTRACT FROM AUTHOR]

A longitudinal survey was conducted in France in a subclinically Salmonella-infected farrow-to-finish pig farm to describe the time-course of the serological response to Salmonella enterica in growing pigs. We used three batches of sows and their corresponding litters (n = 31 litters). Among these, 256 pigs randomly selected and individually identified were followed from the first week of age until slaughter. Serial individual blood samples were submitted to indirect Salmonella-ELISA testing. Salmonella shedding was investigated by bacteriological testing of faecal material regularly collected from the sows and pigs and by environment swabs taken from the pens. Caecal contamination was checked at the slaughterhouse. Information about litter composition (filiation), location of the pigs in post-weaning and fattening pens, sanitary events, sex and body weights was recorded. 11.6% of the pigs shed S. enterica; 52% of pigs seroconverted before slaughter. The age-related variation of the natural logarithm of calibrated optical densities (COD) of pigs was described with two linear mixed models. From 8 to 61 days of age, the decrease in COD with age was fitted with a model including random effects of the animal and the dam on the intercept and slope, a batch random effect on the intercept and an individual birth-weight fixed effect on the intercept. The dam random effect was explained by the parity of the sow, Salmonella shedding by the sow during the farrowing phase and the value of the optical density of colostrum collected at parturition. A second model fitting the increase in COD from 61 days of age until slaughter included the random effect on intercept of the batch and the random effects on slope and intercept of the animal, the dam and the pen in which the followed animals were located during the fattening phase and the environmental contamination as fixed effect. In this second model, no relation was found between individual slaughter-bacteriological results and increasing COD values. Considering seroconversion time between 61 days of age and slaughter, survival function were constructed using the Cox proportional-hazards model. Both methods suggested that seroconversions generally occurred during the last third of the fattening phase (from 140 days of age to slaughter), while shedding was observed during the first half of the fattening period. The fitted models suggest the existence of clusters (such as pen and litter of origin).

The direct immunofluorescent detection of pathogens on pork skin is evaluated. Calibrate contamination of pork skin with Salmonella Typhimurium (ST) and Listeria monocytogenes (Lm) is developed in 2 h at 4 degrees C. Then a specific indirect immunofluorescent staining protocol is optimized in order to obtain specific and intensive signals able to be detected by electronic cameras (deported microscopy). Despite the individual staining of ST and Lm is possible on pork skin and is specific and bright, the deported microscopy failed to detect these particles. After respectively 3 and 6 h, we obtain micro-colonies of ST and Lm. Due to the limited power of the video camera used, only the microscope permits the detection on the skin. However, our work gives standard conditions to mime the pathogens contamination and staining directly on a biological matrix such as pork skin. This work is a first step in the development of direct and rapid detection of pathogens on biological matrix.