Development of a new 1D urban canopy model: coherences between surface parameterizations

A 1-D Canopy Interface Model (CIM) was developed in order to better simulate the effect of urban obstacles on the atmosphere in the boundary layer. The model solves the Navier-Stokes equations on a high-resolved gridded vertical column. The effect of the surface is simulated testing a set of theories and urban parameterizations. The final proposition guarantees its coherence with past theories in any atmospheric stability and terrain configuration. Obstacle characteristics are computed using surface and volume porosities in each cell of the model domain. These porosities are used to weight several terms in the Navier-Stokes equations. A 1.5-order turbulence closure is used in order to compute the turbulent coefficients with the TKE. The mixing length takes into account the density of the obstacles and their height. The turbulent scheme is designed in order to keep CIM coherent with the Prandtl theory in neutral atmospheric conditions and with the MOST in stratified atmospheric stability when CIM is used over plane surfaces. The modifications brought to the main governing equations are discussed following theoretical analysis and experiences with CIM, simulating the averaged meteorological variables (wind speed, turbulent kinetic energy (TKE), temperature and humidity). Simulations are compared with analytical solutions, when possible, and also simulations issued from a computational fluid dynamics (CFD) model. The results show how constant values, usually prescribed, can be theoretically estimated and how the buoyancy term of the turbulent kinetic energy balance equation should be adjusted accordingly. After modifications, it is shown that CIM is coherent with past propositions in any case of atmospheric stabilities over plane surfaces. The use of CIM in presence of obstacles is based on the extension of the 1.5 order turbulence closure to compute the turbulent coefficients with the TKE. CIM shows simulations in good agreement with the CFD simulations in the presence of obstacles. It is able to reproduce an inertial sub-layer as described by the Prandlt and constant-flux layer theory above a displacement height over a homogeneous canopy

Evaluation of building energy use: from the urban to the building scale

A 1-D canopy interface model (CIM) has been developed recently and integrated in the meso-scale meteorological WRF v3.5 model in order to improve the surface representation. One of the objectives of such a model is to prepare for the coupling of micro-scale models with meso-scale models so as to improve building energy consumption estimates at the urban scale as well as improve meteorological variables calculation in urban canyons. The objective of the present study is to evaluate the value of the use of a module able to produce highly resolved vertical profiles of these variables. We will discuss the strategy that will be used to couple the WRF system with the CitySim software. The one-way coupling methodology for the WRF-CIM-CitySim is detailed here. It is expected that the WRF-CIM system can provide enhanced meteorological profiles to CitySim and that this can hence improve the energy consumption calculation at the building scale. This coupled system, could be used by urban planners or architects, as it would provide a significant advantage in the evaluation of building energy use and urban planning scenarios. Future work will focus on a two-way coupling in order to improve the feedback response in the meteorological model

Les Strasbourgeois face à la pollution de l’air

Malgré une tendance à la réduction des émissions de polluants dans l’atmosphère au cours des dernières décennies, dans les pays industrialisés, les populations urbaines sont toujours exposées à des niveaux de pollution dangereux pour leur santé. Dans ce contexte, outre les recherches portant sur les phénomènes physiques, la ZAEU s’est engagée depuis plusieurs années à étudier les « représentations sociales » des risques et particulièrement les risques liés à la pollution de l’air. En effet, la manière dont la lutte contre les pollutions et le réchauffement climatique s’organise est corrélée aux représentations qu’en ont les acteurs sociaux. Ces dernières déterminent aussi grandement les politiques et leur acceptation par la société

The preliminary study of urbanization, fossil fuels consumptions and CO2 emission in Karachi

According to population, Karachi is the first largest city of Pakistan and 9th largest in the world. During last three decades, it has faced mass urbanization, huge population growth, many fold increase in vehicles and industrial development. As a result the demand of more energy in form of fossil fuels increased for domestic, industrial and transportation purpose. In this research the maximum available data of Karachi about urbanization, population and vehicles growth, industrialization, energy consumption and CO2 emissions are analyzed. Time periods considered for this work are according to the availability of the data. The results show that during 1947 to 2008, both urban population and urban area increased to 1500%. During 1990 to 2008, the percentage growth in vehicles is double than that of population growth during this time period. During 1980 to 2007 the consumption of oil and petrol, natural gas and coal increased to 219%, 365% and 287%, respectively. The emission of CO2 jumped from 39 million metric tons in 1980 to 151 million metric tons in 2007

Assimilation de données photochimiques et prévision de la pollution troposphérique

The Chemistry-Transport Models (CTM) are now sufficiently efficient to simulate realistic photochemical pollutant concentrations. Nevertheless, the complexity of involved processes and the temporal and spatial variability of the emission sources make it impossible to perfectly reproduce pollutant concentrations. If an intrinsic parameter or an input is not well described, A huge error results. CHIMERE is a CTM which covers the major part of Europe with a resolution of about fifty kilometers. It offers the possibilty to zoom and simulate pollutant concentrations in a more detailed way over some key regions, such as Ile-de-France and the Berre and Marseille regions. We present results of a comparison of the continental and regional simulations with surface observations and aircraft measurements from the ESQUIF campagne (Etude et Simulation de la QUalité de l'Air en Ile-de-France). This comparison allows us to quantify the total error made in ozone and nitrogen dioxyde concentrations. We also present different methods (e.g. Statistical Interpolation and Kriging) we have tested and adapted to the pollution case in order to correct this error. We compare the methods and show in an objective way that it is possible to obtain more realistic three-dimensional maps of pollutants (e.g. analyses) by combining both simulations and surface observations. A series of real time experiements realized in the PIONEER project show that the forecast error may propagate from one region to another. The european scale ozone analyses are thus used to reinitialize the forecast model. The aim is then to answer the question of whether it possible to improve short time forecasts by using better initial values instead of the forecasts for the day before.Les Modèles de Chimie-Transport (CTM) simulent aujourd'hui de façon assez réaliste les concentrations des espèces responsables de la pollution photochimique estivale. Cependant, la complexité des phénomènes mis en jeu et la variabilité spatiale et temporelle des émissions de polluants sont telles que, quel que soit le modèle utilisé, il est impossible de reproduire parfaitement ces concentrations. Lorsqu'un paramètre interne ou d'entrée du modèle est mal décrit une erreur importante peut etre observée certains jours. Le modèle CHIMERE est un CTM couvrant la majeur partie de l'Europe avec une résolution d'une cinquantaine de kilomètres. Il offre la possibilité de zoomer et de simuler de façon plus détaillée les concentrations des polluants sur des régions clefs, telles que l'Ile-de-France et la région de Berre et de Marseille.Les simulations de ce modèle ont été compaés avec des observations de surface et des données aéroportées de la campagne d'Etude et Simulation de la QUalité de l'Air en Ile-de-France (ESQUIF) à l'échelle européenne et régionale. Cette comparaison a permis ainsi de quantifier l'erreur globale commise sur les concentrations d'ozone et de son précurseur, le dioxyde d'azote. Différentes méthodes (Interpolation Statistique, Krigeage) ont été testées et adaptées au cas de la pollution dans le but de corriger cette erreur. Elles ont été comparées et validées de manière objective. Il a été montré que la combinaison des observations de surface et des simulations du modèle permet d'obtenir efficacement des cartes tridimensionnelles (i.e. des analyses) de concentration des deux polluants, plus réalistes que les simulations brutes.Les expériences menées depuis trois ans dans le cadre du projet PIONEER (Prévisibilité et Incertitude de l'Ozone à l'échelle Européenne et Régionale) montrent que l'erreur de prévision peut éventuellement se propager d'une région vers une autre. Les analyses des concentrations d'ozone, produites à l'échelle européenne ont été également utilisées pour réinitialiser le modèle de prévision. L'objectif était alors de savoir s'il est possible d'améliorer aussi les prévisions à court termes en utilisant de meilleurs états initiaux que les prévisions de la veille

Assimiliation de données photochimiques et prévision de la pollution troposphérique

PALAISEAU-Polytechnique (914772301) / SudocSudocFranceF

Multi-scale modeling of the urban meteorology: Integration of a new canopy model in the WRF model

International audienc