Characterization of aerosol pollution in North of France : relation between mass, optical properties , vertical distribution and meteorology

Une atmosphère saine est un besoin élémentaire pour le bien être et la santé humaine. La matière particulaire en suspension (Particle Matter, PM) est bien connue pour avoir un impact significatif sur la santé. Les mesures de PM2.5 et PM10 au niveau du sol reflètent l’influence de la dynamique de la couche limite et du mélange des aérosols locaux ou advectés sur de grandes distances. Le lien entre épaisseur optique en aerosol (aerosol optical thickness, AOT) et PM dépend de la relation entre propriétés optiques et massiques et de la distribution verticale des particules dans l’atmosphère. Nous présentons 3 expériences de terrain dédiées à la caractérisation des aérosols de pollution dans le Nord de la France: la première lors d’un évenement de pollution printanier sur Lille, la seconde durant un événement de pollution hivernal sur Dunkerque et la troisième durant des occurrences de brise de mer sur le littoral Dunkerquois. Nous avons utilisé 2 systèmes Lidar différents, le premier dans le visible (532 nm) et le second dans l’UV (355 nm); un photomètre solaire automatique et des mesures de PM2.5 et PM10 par TEOM. L’altitude supérieure de la couche de mélange (Mixed boundary layer, MBL) est détectée par Lidar et nous avons été capable de suivre le développement classique de la couche limite convective ainsi que des décroissances brutales d’altitude de la MBL dues à la brise de mer. Les profils d’extinction aérosols ont été estimés en utilisant un rapport Lidar de 67 sr à 532 nm à Lille, 77 sr à 532 nm et 30 sr à 355 nm à Dunkerque. Nous avons analysé l’impact du transport grande échelle de masses d’air polluée, du développement convectif de la MBL et du développement de la cellule de brise de mer sur les profils verticaux d’extinction en aérosols. Le signal Lidar dans les premières centaines de mètres est très bien corrélé (coefficient de corrélation supérieur à 0.9) avec les concentrations massiques mesurées au sol dans tous les cas. Il est également montré que l’introduction de la hauteur de la MBL permet une meilleure détermination des PM à partir de l’épaisseur optique.Clean air is considered to be a basic requirement for human health and well-being. Particulate matter is known to have a significant impact on health. The variability of Particle Matter (PM2.5 and PM10) concentrations recorded at ground-level is influenced by the boundary layer dynamics, local emissions, and advection and mixing of large scale transported aerosols. The link between columnar aerosol optical thickness (AOT) and ground-level PM depends on the relationship between mass and optical properties and on the vertical distribution of aerosols in the atmosphere. We present three field experiments dedicated to the characterization of pollution aerosols in the North of France: the first one during a spring pollution episode in metropolitan area of Lille (50.61°N, 3.14°E), the second one during a winter pollution episode in the industrial coastal city of Dunkerque (51°04'N; 2°38'E) and the third one during summer sea breezes on coastal area of Dunkerque. We have used 2 different Lidar systems, one in the UV (355 nm) and the other one in the visible (532 nm), an automatic sun photometer, and PM2.5 and PM10 measurements with TEOM. The mixed layer (MBL) top altitude is detected from the Lidar signal and we were able to monitor the classical diurnal evolution of the convective continental boundary as well as short-time decreases in the MBL height due to sea breeze occurrences. The aerosol extinction profiles were estimated using a Lidar ratio of 67 sr at 532 nm in Lille, and 77 sr at 532 nm and 30 sr at 355 m in Dunkerque. We have analyzed the impact of long range transport of polluted air masses, convective development of the MBL, and sea breeze development on the vertical profile of aerosol extinction coefficient. The Lidar signal in the first few hundred meters is well correlated (correlation coefficient above 0.9) with the PM concentrations in all cases. It is found that introducing the Lidar derived MBL height enable a better estimation of PM from measured AOT. Clean air is considered to be a basic requirement for human health and well-being. Particulate matter is known to have a significant impact on health. The variability of Particle Matter (PM2.5 and PM10) concentrations recorded at ground-level is influenced by the boundary layer dynamics, local emissions, and advection and mixing of large scale transported aerosols. The link between columnar aerosol optical thickness (AOT) and ground-level PM depends on the relationship between mass and optical properties and on the vertical distribution of aerosols in the atmosphere. We present three field experiments dedicated to the characterization of pollution aerosols in the North of France: the first one during a spring pollution episode in metropolitan area of Lille (50.61°N, 3.14°E), the second one during a winter pollution episode in the industrial coastal city of Dunkerque (51°04'N; 2°38'E) and the third one during summer sea breezes on coastal area of Dunkerque. We have used 2 different Lidar systems, one in the UV (355 nm) and the other one in the visible (532 nm), an automatic sun photometer, and PM2.5 and PM10 measurements with TEOM. The mixed layer (MBL) top altitude is detected from the Lidar signal and we were able to monitor the classical diurnal evolution of the convective continental boundary as well as short-time decreases in the MBL height due to sea breeze occurrences. The aerosol extinction profiles were estimated using a Lidar ratio of 67 sr at 532 nm in Lille, and 77 sr at 532 nm and 30 sr at 355 m in Dunkerque. We have analyzed the impact of long range transport of polluted air masses, convective development of the MBL, and sea breeze development on the vertical profile of aerosol extinction coefficient. The Lidar signal in the first few hundred meters is well correlated (correlation coefficient above 0.9) with the PM concentrations in all cases. It is found that introducing the Lidar derived MBL height enable a better estimation of PM from measured AOT

Characterization of aerosol pollution in North of France (relation between mass, optical properties , vertical distribution and meteorology)

Une atmosphère saine est un besoin élémentaire pour le bien être et la santé humaine. La matière particulaire en suspension (Particle Matter, PM) est bien connue pour avoir un impact significatif sur la santé. Les mesures de PM2.5 et PM10 au niveau du sol reflètent l influence de la dynamique de la couche limite et du mélange des aérosols locaux ou advectés sur de grandes distances. Le lien entre épaisseur optique en aerosol (aerosol optical thickness, AOT) et PM dépend de la relation entre propriétés optiques et massiques et de la distribution verticale des particules dans l atmosphère. Nous présentons 3 expériences de terrain dédiées à la caractérisation des aérosols de pollution dans le Nord de la France: la première lors d un évenement de pollution printanier sur Lille, la seconde durant un événement de pollution hivernal sur Dunkerque et la troisième durant des occurrences de brise de mer sur le littoral Dunkerquois. Nous avons utilisé 2 systèmes Lidar différents, le premier dans le visible (532 nm) et le second dans l UV (355 nm); un photomètre solaire automatique et des mesures de PM2.5 et PM10 par TEOM. L altitude supérieure de la couche de mélange (Mixed boundary layer, MBL) est détectée par Lidar et nous avons été capable de suivre le développement classique de la couche limite convective ainsi que des décroissances brutales d altitude de la MBL dues à la brise de mer. Les profils d extinction aérosols ont été estimés en utilisant un rapport Lidar de 67 sr à 532 nm à Lille, 77 sr à 532 nm et 30 sr à 355 nm à Dunkerque. Nous avons analysé l impact du transport grande échelle de masses d air polluée, du développement convectif de la MBL et du développement de la cellule de brise de mer sur les profils verticaux d extinction en aérosols. Le signal Lidar dans les premières centaines de mètres est très bien corrélé (coefficient de corrélation supérieur à 0.9) avec les concentrations massiques mesurées au sol dans tous les cas. Il est également montré que l introduction de la hauteur de la MBL permet une meilleure détermination des PM à partir de l épaisseur optique.Clean air is considered to be a basic requirement for human health and well-being. Particulate matter is known to have a significant impact on health. The variability of Particle Matter (PM2.5 and PM10) concentrations recorded at ground-level is influenced by the boundary layer dynamics, local emissions, and advection and mixing of large scale transported aerosols. The link between columnar aerosol optical thickness (AOT) and ground-level PM depends on the relationship between mass and optical properties and on the vertical distribution of aerosols in the atmosphere. We present three field experiments dedicated to the characterization of pollution aerosols in the North of France: the first one during a spring pollution episode in metropolitan area of Lille (50.61N, 3.14E), the second one during a winter pollution episode in the industrial coastal city of Dunkerque (5104'N; 238'E) and the third one during summer sea breezes on coastal area of Dunkerque. We have used 2 different Lidar systems, one in the UV (355 nm) and the other one in the visible (532 nm), an automatic sun photometer, and PM2.5 and PM10 measurements with TEOM. The mixed layer (MBL) top altitude is detected from the Lidar signal and we were able to monitor the classical diurnal evolution of the convective continental boundary as well as short-time decreases in the MBL height due to sea breeze occurrences. The aerosol extinction profiles were estimated using a Lidar ratio of 67 sr at 532 nm in Lille, and 77 sr at 532 nm and 30 sr at 355 m in Dunkerque. We have analyzed the impact of long range transport of polluted air masses, convective development of the MBL, and sea breeze development on the vertical profile of aerosol extinction coefficient. The Lidar signal in the first few hundred meters is well correlated (correlation coefficient above 0.9) with the PM concentrations in all cases. It is found that introducing the Lidar derived MBL height enable a better estimation of PM from measured AOT. Clean air is considered to be a basic requirement for human health and well-being. Particulate matter is known to have a significant impact on health. The variability of Particle Matter (PM2.5 and PM10) concentrations recorded at ground-level is influenced by the boundary layer dynamics, local emissions, and advection and mixing of large scale transported aerosols. The link between columnar aerosol optical thickness (AOT) and ground-level PM depends on the relationship between mass and optical properties and on the vertical distribution of aerosols in the atmosphere. We present three field experiments dedicated to the characterization of pollution aerosols in the North of France: the first one during a spring pollution episode in metropolitan area of Lille (50.61N, 3.14E), the second one during a winter pollution episode in the industrial coastal city of Dunkerque (5104'N; 238'E) and the third one during summer sea breezes on coastal area of Dunkerque. We have used 2 different Lidar systems, one in the UV (355 nm) and the other one in the visible (532 nm), an automatic sun photometer, and PM2.5 and PM10 measurements with TEOM. The mixed layer (MBL) top altitude is detected from the Lidar signal and we were able to monitor the classical diurnal evolution of the convective continental boundary as well as short-time decreases in the MBL height due to sea breeze occurrences. The aerosol extinction profiles were estimated using a Lidar ratio of 67 sr at 532 nm in Lille, and 77 sr at 532 nm and 30 sr at 355 m in Dunkerque. We have analyzed the impact of long range transport of polluted air masses, convective development of the MBL, and sea breeze development on the vertical profile of aerosol extinction coefficient. The Lidar signal in the first few hundred meters is well correlated (correlation coefficient above 0.9) with the PM concentrations in all cases. It is found that introducing the Lidar derived MBL height enable a better estimation of PM from measured AOT.LILLE1-Bib. Electronique (590099901) / SudocSudocFranceF

Impact of sea breeze on vertical structure of aerosol optical properties in Dunkerque, France

International audienceDuring July 2008, we used an elastic backscattering LIDAR to monitor the aerosol vertical distribution at the coastal area of Dunkerque, France. Here we report the sea breeze event which was observed with more highlighted effect of aerosol on 25 July. By combining LIDAR measurements with Sun photometer-retrieved aerosol optical thickness, we estimated an average LIDAR ratio of 33 sr (± 14 sr) for the estimation of aerosol extinction profiles during the sea breeze. The LIDAR derived aerosol extinction in the first 200 m is clearly affected by the sea breeze and increases by more than 100% at the time of sea breeze arrival. A sharp convective boundary layer height decrease is observed in the LIDAR data due to the formation of the thermal internal boundary layer in the lowest part of the sea-to-land flow. PM2.5 concentration increases due to the thermal internal boundary layer formation and reaches its maximum between 1 and 2h after the front overpass. Except during the front overpass, the PM2.5 is well correlated to the inverse of the mixing height detected by the LIDAR

Impact of the mixing boundary layer on the relationship between PM2.5 and aerosol optical thickness

International audienceThe purpose of this paper is to study the relationship between columnar aerosol optical thickness and ground-level aerosol mass. A set of Sun photometer, elastic backscattering lidar and TEOM measurements were acquired during April 2007 in Lille, France. The PM2.5 in the mixed boundary layer is estimated using the lidar signal, aerosol optical thickness, or columnar integrated Sun photometer size distribution and compared to the ground-level station measurements. The lidar signal recorded in the lowest level (240 m) is well correlated to the PM2.5 (R 2 ¼ 0.84). We also show that the correlation between AOT-derived and measured PM2.5 is significantly improved when considering the mixed boundary layer height derived from the lidar. The use of the Sun photometer aerosol fine fraction volume does not improve the correlation

Stratus-Fog Formation and Dissipation: A 6-Day Case Study

15th international symposium for the advancement of boundary-layer remote sensing (ISARS), 28-30 June 2010, Paris, FranceInternational audienceA suite of active and passive remote sensing instruments and in-situ sensors deployed at the SIRTA Observatory (Instrumented Site for Atmospheric Remote Sensing Research), near Paris, France, for a period of six months (October 2006-March 2007) document simultaneously radiative, microphysical and dynamic processes driving the continental-fog life cycle. The study focuses on a 6-day period between 23 and 29 December 2006 characterized by several stratus-cloud lowering and lifting events and almost 18 h of visibility below 1 km. Conceptual models and different possible scenarios are presented here to explain the formation, the development and the dissipation phases of three major stratus-fog events and to quantify the impact of each driving process. For example, slowly evolving large-scale conditions characterized by a slow continuous cloud-base lowering, followed by a rapid transient period conductive to fog formation and dissipation, are observed for cases 1 and 3. During this stable period, continuous cloud-top radiative cooling (≈ -160 Wm-2) induces a progressive and slow lowering of the cloud base: larger droplets at cloud top (cloud reflectivity approximately equals to -20 dBZ) induce slow droplet fall to and beyond cloud base (Doppler velocity ≈ -0.1 ms-1), cooling the sub-cloud layer by evaporation and lowering the saturation level to 100 m (case 1) or to the surface (cases 2 and 3). Suddenly, a significant increase in Doppler velocity magnitude ≈ -0.6 ms-1 and of turbulent kinetic energy dissipation rate around 10-3 m2s-3 occurs at cloud base (case 1). These larger cloud droplets reach the surface leading to fog formation over 1.5 h. The Doppler velocity continues to increase over the entire cloud depth with a maximum value of around -1 ms-1 due to the collection of fog droplets by the drizzle drops with high collection efficiency. As particles become larger, they fall to the ground and lead to fog dissipation. Hence, falling particles play a major role in both the formation and also in the dissipation of the fog. These roles co-exist and the balance is driven by the characteristics of the falling particles, such as the concentration of drizzle drops, the size distribution of drizzle drops compared to fog droplets, Doppler velocity and thermodynamic state close to the surface