Publications by Alain Clappier

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Two versions of the Emission Inventory (EI) are generated for the city of Bogota, Colombia. In the first version (EI-1), CORINAIR traffic emission factors (EFs) are used. In the second (EI-2), bulk traffic EF's calculated for the city, using in situ measur ...

Road traffic emissions, one of the largest source categories in megacity inventories, are highly uncertain. It is essential to develop methodologies to reduce these uncertainties to manage air quality more effectively. In this paper, we propose a methodolo ...

The Grenoble metropolitan area located in the French Alps with more than 400 thousand inhabitants suffers from periods of high ozone (O3) concentrations in summertime. Grenoble is moreover located in the Y shaped convergence of three deep valleys with surrounding mountains up to 3 000 m above sea level (asl) leading to a very complex wind pattern. During summer 1999, a major field campaign GRENOble PHOTochemistry (GRENOPHOT) involving standard ground based stations, LIDAR, aircraft, DOAS, microwave windprof

The Grenoble metropolitan area located in the French Alps with more than 400 thousand inhabitants suffers from periods of high ozone (O3) concns. in summertime. Grenoble is moreover located in the Y shaped convergence of three deep valleys with surrounding mountains up to 3,000 m above sea level (asl) leading to a very complex wind pattern. During summer 1999, a major field campaign GRENOble PHOTochem. (GRENOPHOT) involving std. ground based stations, LIDAR, aircraft, DOAS, microwave windprofilers was carri

Numerical simulations compared with field measurements are used to explain the effect of sea breezes on photochemical smog episodes in Athens during the Mediterranean Campaign of Photochemical Tracers on 12-14 September 1994. The numerical simulations, performed using a nonhydrostatic vorticity mesoscale model coupled to the Lurmann-Carter-Coyner photochemical module, are compared with ground-based lidar and aircraft measurements. The current analysis shows that the three selected days include the two main

In Havana, transport is blamed as a likely source of pollution issues. which is usually supported on arguments referring to a vehicle fleet mainly made of old cars (i.e., most models are American from the 1950s or Russian from the 1980s) with poor technica ...

The generation of heat in buildings, and the way this heat is exchanged with the exterior, plays an important role in urban climate. To analyze the impact on urban climate of a change in the urban structure, it is necessary to build and use a model capable ...

Hydroxyl radicals dominate daytime tropospheric chem., responsible for reactive removal of most trace gases (e.g., volatile org. compds.[VOC]), and is an active participant in the NO and NO2 cycle. Pump-and-probe LIDAR was used to examine the OH- chem. in the planetary boundary layer. This method consists of a high OH- concn. prodn. by a first laser beam (pump), including a flash photolysis of O3: O3 + hv (256 nm) -> O(1D) + O2, and the reaction, O(1D) + H2O -> 2OH. Its relaxation is followed by measuring t

Road traffic emission factors (EFs) are one of the main sources of uncertainties in emission inventories; it is necessary to develop methods to reduce these uncertainties to manage air quality more efficiently. Recently an alternative method has been propo ...

Preliminary work confirmed the important contribution of regional scale processes on pollutant concns. obsd. at local scales. For Grenoble, France, the model domain for simulations discussed, was selected considering the topog., urban area distribution, boundary conditions, and possible constraints in terms of computing time. The nesting technique used involved calcns. over a larger domain which contained the smaller domain. Two of the most important components of these models are the chem. mechanism and tr

An episode selection procedure was developed and applied to select sets of days representing characteristic meteorol. conditions leading to high ozone episodes over the Swiss Plateau. The selection procedure was applied to data extending from Jan. 1991 through Dec. 1998, and is comprised of two steps: First, days were classified according to obsd. air quality and meteorol. characteristics using classification and regression trees anal. (CART). Second, the CART results were used in conjunction with obsd. air

The increased resolution of numerical weather prediction models allows nowadays addressing more realistically urban meteorology and air pollution processes. This has triggered new interest in modelling and describing experimentally the specific features an ...

A 1D Canopy Interface Model (CIM) is developed to act as an interface between a meso-scale and a micro-scale atmospheric model and to better resolve the surface turbulent fluxes in the urban canopy layer. A new discretisation is proposed to solve the TKE e ...

A new indicator is proposed to det. whether tropospheric O3 prodn. in a specific area is limited by volatile org. compds. (VOC) or NOx. This indicator, tVOCOH/tNOxOH, describes the ratio of OH- lifetime vs. losses by reaction with VOC and NOx. Whereas tNOxOH can be obtained by conventional measurements, the new pump and probe OH approach makes it possible to also obtain tVOCOH. Indicator values above a threshold value of 0.2 +- 50% are representative of NOx-satd. conditions, where an increase of NOx emissio

A new method to investigate atmospheric chemical kinetics is presented. It is based on the pump and probe principle. Preliminary measurements are described on the decay rate of OH in the planetary boundary layer its concentration has been raised by laser flash photolysis of background ozone and subsequent reaction of the O(1D) with atmospheric water vapor. The measured OH disappearance kinetics are compared with model calculations yielding information on the fast reaction of OH. The presented point measurem

The first combined reconstruction of range-resolved wind velocities and O3 concns. is presented from the anal. of a single DIAL data set analyzed with a correlation method to det. wind speeds. The system can be used for the measurement of a unique component of the wind velocity with an accuracy comparable to that of stand-alone fixed beam correlation lidar instruments. A photochem. model is also developed to predict the spatio-temporal evolution of O3 concns., originated by both chem. and transport effects.

During the Limitation of Oxidant Prodn. (LOOP) campaign, different instruments were deployed, providing a complete data set. This will be used to evaluate the model and its ability to reproduce pollution events. Then, the complete data set will be used for a better definition of the model inputs. The final aim of the LOOP project is to use the model to test different abatement strategies, particularly by defining the region where ozone prodn. is NOx or VOC sensitive.

Eulerian photochem. grid models are widely used in the making of policy decisions concerning emission controls. However, significant uncertainties persist in a host of crucial input parameters. Quantifying and understanding their implications have become imperative from both the scientific and policy perspectives. Meteorol. uncertainties have a special significance because efforts to quantify them using conventional techniques based on expert ests. have failed to account for the complex correlations in thei

The links between air pollution gas phase chem., aerosol chem. processes, and solar radiation are calcd. to improve air quality models. Air quality models are used to simulate pollutant content of the city plumes such as for Los Angeles.

OH- radical reactivity with total volatile org. compds. (VOC), SkVOC[VOC], is directly obtained in the planetary boundary layer (PBL). A method is based on a perturbation technique where high initial OH- concns. are created by flash photolysis of O3 and subsequent reaction of O(1D) with H2O. Laser-induced fluorescence measures residual OH- concn. at different time delays after the perturbation (

Alain Clappier

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Air quality modelling over Bogota, Colombia: Combined techniques to estimate and evaluate emission inventories

Estimation of road traffic emission factors from a long term tracer study

Étude d'un épisode photochimique à l'aide d'un modèle méso-échelle et de mesures intensives sur la région de Grenoble

Study of a photochemical episode over the Grenoble area using a mesoscale model and intensive measurements

Effect of sea breeze on air pollution in the greater Athens area. Part I: Numerical simulations and field observations

Evidence of traffic-generated air pollution in Havana

A new building energy model coupled with an urban canopy parameterization for urban climate simulations-part I. formulation, verification, and sensitivity analysis of the model

In-situ OH kinetics study providing an indicator for ozone formation limitation

An evaluation of the estimation of road traffic emission factors from tracer studies

Measurement campaign and numerical modelling in the complex topography of the Grenoble area (France) during summer '99

Episode selection for ozone modelling and control strategies analysis on the Swiss Plateau

Towards improving the simulation of meteorological fields in urban areas through updated/advanced surface fluxes description

On the Coherence in the Boundary Layer: Development of a Canopy Interface Model

Total VOC reactivity in the planetary boundary layer 2. A new indicator for determining the sensitivity of the ozone production to VOC and NOx

Direct measurement of the total reaction rate of OH in the atmosphere

Ozone flux measurements in the troposphere with a shot per shot DIAL instrument operated in the UV spectral region during the MEDCAPHOT campaign

Photo-oxidant formation in the Milan metropolitan area

Uncertainties in photochemical grid modeling of ozone. The impact of uncertainties in meteorological inputs

Numerical simulation of the links between air pollution, aerosols and solar radiation

Total VOC reactivity in the planetary boundary layer 1. Estimation by a pump and probe OH experiment