多尺度空气质量模式系统及其验证 I.模式系统介绍与气象要素模拟

A Multi-Scale Air Quality Modeling System and Its Evaluation I. Introduction to the Model System and Simulation of Meteorological Parameters

主要介绍一个多尺度空气质量模式系统及其在东亚地区的应用。这套模式系统充分考虑了天气系统与中、小尺度气象过程对污染物的输送、扩散、转化和迁移过程的影响,区域与城市尺度之间大气污染物的相互影响,以及污染物在大气中的气相与液相化学过程、非均相化学过程、气溶胶过程和干湿沉积过程对浓度分布的影响,可用于区域与城市尺度对流层臭氧、大气气溶胶、能见度和其他空气污染物的预报和环境评价。模拟的气象要素(风向、风速、温度和湿度)与TRACE-P和ACE-Asia期间三架飞机上获取的观测资料的比较结果表明,模拟值与其相应的观测值具有非常好的一致性,它们的相关系数都超过了0·96。

A multi-scale air quality modeling system and its application to East Asia are introduced. This modeling system consisting of two major components, the Model-3 Community Multi-scale Air Quality modeling system （CMAQ） and the Regional Atmospheric Modeling System （RAMS）, has the capability to take into account the influences of synoptic weather system and meso- and micro-scale meteorological processes upon transport, diffusion, transformation and deposition of atmospheric pollutants, the interactions of the pollutants in regional and urban scales, and the impacts of gaseous, aqueous and heteorogeneous chemistry, aerosol processes and deposition upon spatial-temporal concentration distributions of the pollutants, and can be used to forecast tropospheric ozone and aerosol concentrations, visibility and mixing ratios of other pollutants and assess air quality in regional and urban scales. In this application CMAQ is configured with the chemical mechanism of the Regional Acid Deposition Model version 2 （RADM2）, including organic aerosol processes from direct emissions and production from long-chain alkanes, alkyl-substituted benzene, etc. To depict aerosol evolution processes in the atmosphere, the aerosol module, a major extension of the Regional Particulate Model （RPM）, is included. In the module the particle size distribution is represented as the superposition of three lognormal sub-distributions, and the processes of coagulation, particle growth by the addition of new mass, particle formation, dry deposition, cloud processing, aerosol chemistry, etc.are included. While regional three-dimensional meteorological fields including boundary-layer turbulence, cloud and precipitation necessary for CMAQ simulations are provided by RAMS instead of the default meteorological driver MM5. With the modeling system, meteorological fields and three-dimensional distributions of trace gases and aerosols over East Asia during the period 22 April to 05 May 2001 are simulated. During the simulations, three dimensional meteorological fields for the RAMS inputs are obtained from the European Center for Medium-range Weather Fore- cast （ECMWF） 1°×1°reanalysis datasets, and they are available every six hours. For CMAQ, the anthropogenic emissions of nitrogen oxides, carbon monoxide, volatile organic compounds （VOCs） and sulfur dioxide are obtained from the emission inventory of 1°×1°specially prepared to support the projects of the Transport and Chemical Evolution over the Pacific （TRACE-P） and the Aerosol Characterization Experiment-Asia （ACE-Asia） and from the Emission Database for Global Atmospheric Research （EDGAR）. In order to evaluate the model performance, model results including meteorological parameters （such as wind speed and direction, temperature and water vapor content） and concentrations of some trace gases and aerosols （such as ozone, OH radicals, carbon monoxide, nitrogen oxides, ethane, sulfate and nitrate aerosols） are compared with observations obtained from instruments on board three aircraft during the TRACE-P and the ACE-Asia field campaigns being conducted over a broad area covering northeastern Asia and the western Pacific in the springtime of 2001. In comparing the model results with the aircraft measurements, the model results are sampled along flight tracks and with a 1 hour temporal resolution. Comparison of the simulated meteorological parameters （such as wind speed and direction, temperature and specific humidity） with the observations shows that the modeled meteorology reproduces quantitatively most of the major observed features. For example, the correlation coefficients for wind speed and direction, temperature and specific humidity each exceed 0. 96 for all TRACE-P and ACE-Asia observation points. Comparison results about trace gases and aerosols are analyzed in companion papers.