Evaluation of ozonesondes, HALOE, SAGE II and III, Odin- OSIRIS and -SMR, and ENVISAT-GOMOS, -SCIAMACHY and -MIPAS ozone profiles in the tropics from SAOZ long duration balloon measurements in 2003 and 2004

International audienceThe performances of satellite and sondes ozone measuring instruments available in the tropics between 10 and 26 km during the southern hemisphere summer in 2003 and 2004, have been investigated by comparison with series of profiles obtained by solar occultation in the visible Chappuis bands using a SAOZ UV-Vis spectrometer carried by long duration balloons. When compared to SAOZ, systematic positive or negative altitude shifts are observed in the satellite profiles, varying from <50 m for the GOMOS v6.0b stellar occultation instrument, followed by +100/200 m for solar occultation systems (SAGE II v6.2, HALOE v19 above 22 km), but as large as -900 m for the OSIRIS limb viewing system. The ozone relative biases are generally limited, between -4% and +4%, for measurements in the visible Chappuis bands (SAGE II and SAGE III moon v3, GOMOS above 22 km and OSIRIS), the near IR (HALOE above 22 km) and the ozonesondes, but increase to +5.5% (SCIAMACHY IUP v1.63) though still in the visible, and +7% in the mid-IR (MIPAS NL v4.61) and the submillimetric range (SMR v222). Regarding precision, evaluated statistically from the zonal variability of ozone concentration, the best measurements are found to be those of SAGE II (2%), followed by HALOE above 22 km (3–4%), then the ozonesondes, SAGE III moon, SCIAMACHY and OSIRIS (4–5%), GOMOS above 22 km (~6%), MIPAS (8.5%) and finally SMR (16%). Overall, all satellite ozone measurements appear to be of little utility in the tropical troposphere except those of SAGE II (and eventually SAGE III), though low biased by 50% and of limited (50%) precision

Impact of vertical transport processes on the tropospheric ozone layering above Europe. Part I: Study of air mass origin using multivariate analysis, clustering and trajectories

A new method is proposed to classify ozone-rich layers observed in tropospheric profiles in terms of their origin using multivariate analysis. We combine principal component and discriminant analyses to quantify the respective ability of 21 measured physical parameters to describe the layers. Agglomerative hierarchical clustering shows the existence of clusters of air masses with specific physical characteristics. Quadratic discriminant analysis allows the definition of multidimensional borders between these clusters. The geophysical characteristics of the clusters are discussed and related to the origins of the layers: recently transported from the stratosphere (ST) or from the boundary layer (BL) or transported over long distances in the free troposphere. This clustering is compared to the results of a Lagrangian particle dispersion model for a 2-year period. The proportions of layers originating either from the BL or from the ST are highly consistent using both methods as well as the respective contribution of each reservoir to the total ozone mass. About 10% of the ozone measured in the tropospheric layers was exported recently from the BL and one-fifth has a recent stratospheric origin. The remaining proportion could not be attributed to any recent transport pathway. Season-dependent criteria allow very satisfactory reproduction of the seasonal variability of the layering as seen by the Lagrangian model. Analysis of the geographical origin of BL air masses suggests that the statistical clustering underestimates long-range transport, especially in fall

Detecting variability changes in Arctic total ozone column

International audienceTo better assess inter-annual variance changes in ozone time series, we study and propose a statistical procedure based on recent advances in wavelet multi-resolution analysis. This approach, novel to the field of ozone analysis, has the advantages of detecting significant changes in variance and of characterizing the distribution of these changes, including not only their timings but also their strengths.As a test case for our method, we study total ozone column time series from the TOMS (Total Ozone Mapping Spectrometer) Version 7 in the Arctic region over the period 1981–1992. This statistical procedure allows us to analyse the well-known winter–spring transition and the inter-annual variability behaviour. For this specific example, two distinct types of winter–spring transition can be clearly identified for the ozone series. As expected from dynamical studies of the vortex evolution, the first type is constituted of the years for which there exists a very abrupt and temporally localized ozone variability change. More precisely, we detect a significant peak in ozone variance at two multi-resolution wavelet levels. The second type is characterized by smooth ozone variance changes over time and space. Moreover, the Arctic vortex breakdown timing seems to occur, on average, 1 month earlier than our detected changes in ozone variability. These results suggest a potential link between these two phenomena

Evaluation of SHADOZ sondes, HALOE and SAGE II ozone profiles at the tropics from SAOZ UV-Vis remote measurements onboard long duration balloons

International audienceLong series of ozone profiles from 6 to 28 km at the Southern Tropics have been obtained from solar occultation measurements at twilight using a SAOZ spectrometer borne by long duration balloons. Two flights have been performed from Bauru in Brazil both in the summer, in February and March 2001 and 2003, from where the balloons are moving westward at almost constant latitude (20°±5° S). The flight in 2001 passed right over Reunion Island where the SAOZ measurements could be compared to those of both tropospheric and stratospheric ozone lidars. In the stratosphere, compared to that of SAOZ, the measurements of the SHADOZ ozonesondes network, and the HALOE and SAGE II instruments in orbit are found a little noisier (2–3% for SAGE II, 3–4% for HALOE, 4–5% for the sondes), and of insignificant or small high biased (SAGE II). No differences in altitude could be found between SAOZ and SAGE II at all levels, and HALOE above 22 km. But the ozonesondes appear to be systematically displaced upwards by some 400–700 m at all levels, and the HALOE profiles do show an increasing altitude bias at decreasing altitude below 22 km. In the upper troposphere, the SAOZ measurements are found consistent with those of the sondes at Reunion Island and high biased on average over the Western Pacific, at American Samoa and Fiji. Compared to SAOZ, SAGE II shows a 50–60% low bias similar to that already found with the ozonesondes, and a 2–2.5 times larger zonal variability, suggesting a degradation of its precision below the tropopause. Finally, the unrealistic large offsets and variability in the HALOE data compared to all others suggest that its measurements are no reliable in the tropical troposphere below 17 km

Cirrus Classification at Midlatitude from Systematic Lidar Observations

Systematic cirrus lidar measurements performed in the south of France during 2000 are analyzed statistically to search for cloud classes. The classes are based on cloud characteristics (cloud thickness, light backscattering efficiency, and its variance), cloud absolute geometric height, cloud height relative to the tropopause, and the temperature at the cloud level. The successive use of principal component analysis, cluster methods, and linear discriminant analysis allows the identification of four cirrus classes. Almost all the cirrus detections correspond to three classes with similar proportion of the total cirrus detected (around 30%). The absolute geometric height and the thickness are found to be the main discriminant variables. The first cirrus class corresponds to thin clouds above the local tropopause (absolute geometric height: 11.5 km), or at least around the tropopause, while another class corresponds also to thin clouds but at a lower altitude range in the troposphere (absolute geometric height: 8.6 km). The third class corresponds to thick clouds (thickness of 3.2 km) located below the tropopause, in an altitude range between the two first classes (absolute geometric height: 9.8 km). As expected, the high-altitude cirrus class is characterized with the lowest mean temperature. It is noted that the temperature is closely related to the altitude and so the role of temperature in the cirrus classes cannot be disentangled from the role of the altitude

Valorisation de la digitalisation des séries pluviographiques anciennes. Apport pour l’estimation des précipitations extrêmes en France

Les séries pluviométriques infra-quotidiennes disponibles dans la base de données climatologiques de Météo-France sont généralement de durée assez courte pour l’estimation locale des valeurs extrêmes (moins de 20 ans) tandis que d’importants fonds documentaires au format papier existent dans les archives des Centres Départementaux et des différents gestionnaires de réseau. Dans le cadre du projet EXTRAFLO, subventionné par l’Agence Nationale de la Recherche (ANR), Météo-France a validé en contexte opérationnel, un outil moderne de digitalisation des pluviogrammes, nommé Digitalise. Des actions de digitali-sation de plusieurs longues séries ont été engagées pour évaluer leur apport pour la connaissance des valeurs extrêmes. Après avoir vérifié les conditions d’utilisation de la méthode, une procédure de validation des données a été définie. La comparaison des données pluviographiques anciennes aux observations quotidiennes des pluviomètres met en évidence quelques biais significatifs dans les différentes gammes d’intensité, bien corrélées avec le type d’instrument utilisé. Ces nouvelles séries présentent toutefois un grand intérêt pour l’estimation des extrêmes pluviométriques notamment aux pas de temps infra quotidien, avec une réduction significative des intervalles de confiance liée à l’allongement des chroniques Sur la base de ces résultats, un programme de saisie de séries pluviographiques anciennes est en cours de définition avec les services régionaux de Météo-France et pourra être étendu aux partenaires intéressés pouvant bénéficier de la mise à disposition gracieuse du logiciel Digitalise

Rift Valley fever dynamics in Senegal: a project for pro-active adaptation and improvement of livestock raising management

The multi-disciplinary French project “Adaptation à la Fièvre de la Vallée du Rift” (AdaptFVR) has concluded a 10-year constructive interaction between many scientists/partners involved with the Rift Valley fever (RVF) dynamics in Senegal. The three targeted objectives reached were (i) to produce - in near real-time - validated risk maps for parked livestock exposed to RVF mosquitoes/vectors bites; (ii) to assess the impacts on RVF vectors from climate variability at different time-scales including climate change; and (iii) to isolate processes improving local livestock management and animal health. Based on these results, concrete, pro-active adaptive actions were taken on site, which led to the establishment of a RVF early warning system (RVFews). Bulletins were released in a timely fashion during the project, tested and validated in close collaboration with the local populations, i.e. the primary users. Among the strategic, adaptive methods developed, conducted and evaluated in terms of cost/benefit analyses are the larvicide campaigns and the coupled bio-mathematical (hydrological and entomological) model technologies, which are being transferred to the staff of the “Centre de Suivi Ecologique” (CSE) in Dakar during 2013. Based on the results from the AdaptFVR project, other projects with similar conceptual and modelling approaches are currently being implemented, e.g. for urban and rural malaria and dengue in the French Antille

An overview of the HIBISCUS campaign

International audienceThe EU HIBISCUS project consisted of a series of field campaigns during the intense convective summers in 2001, 2003 and 2004 in the State of São Paulo in Brazil. Its objective was to investigate the impact of deep convection on the Tropical Tropopause Layer (TTL) and the lower stratosphere by providing a new set of observational data on meteorology, tracers of horizontal and vertical transport, water vapour, clouds, and chemistry in the tropical Upper Troposphere/Lower Stratosphere (UT/LS). This was achieved using short duration research balloons to study local phenomena associated with convection over land, and long-duration balloons circumnavigating the globe to study the contrast between land and oceans. Analyses of observations of short-lived tracers, ozone and ice particles show strong episodic local updraughts of cold air across the lapse rate tropopause up to 18 or 19 km (420-440 K) in the lower stratosphere by overshooting towers. The long duration balloon and satellite measurements reveal a contrast between the composition of the lower stratosphere over land and oceanic areas, suggesting significant global impact of such events. The overshoots are shown to be well captured by non-hydrostatic meso-scale Cloud Resolving Models indicating vertical velocities of 50-60 m s−1 at the top of the Neutral Buoyancy Level (NBL) at around 14 km, but, in contrast, are poorly represented by global Chemistry-Transport Models (CTM) forced by Numerical Weather Forecast Models (NWP) underestimating the overshooting process. Finally, the data collected by the HIBISCUS balloons have allowed a thorough evaluation of temperature NWP analyses and reanalyses, as well as satellite ozone, nitrogen oxide, water vapour and bromine oxide measurements in the tropics