An overview of the MILAGRO 2006 Campaign: Mexico City emissions and their transport and transformation

Abstract

Abstract. MILAGRO (Megacity Initiative: Local And Global Research Observations) is an international collaborative project to examine the behavior and the export of atmospheric emissions from a megacity. The Mexico City Metropolitan Area (MCMA) -one of the world's largest megacities and North America's most populous city -was selected as the case study to characterize the sources, concentrations, transport, and transformation processes of the gases and fine particles emitted to the MCMA atmosphere and to evaluate the regional and global impacts of these emissions. The findings of this study are relevant to the evolution and impacts of pollution from many other megacities.The measurement phase consisted of a month-long series of carefully coordinated observations of the chemistry and physics of the atmosphere in and near Mexico City duringCorrespondence to: L. T. Molina (ltmolina@mit.edu) March 2006, using a wide range of instruments at ground sites, on aircraft and satellites, and enlisting over 450 scientists from 150 institutions in 30 countries. Three ground supersites were set up to examine the evolution of the primary emitted gases and fine particles. Additional platforms in or near Mexico City included mobile vans containing scientific laboratories and mobile and stationary upward-looking lidars. Seven instrumented research aircraft provided information about the atmosphere over a large region and at various altitudes. Satellite-based instruments peered down into the atmosphere, providing even larger geographical coverage. The overall campaign was complemented by meteorological forecasting and numerical simulations, satellite observations and surface networks. Together, these research observations have provided the most comprehensive characterization of the MCMA's urban and regional atmospheric composition and chemistry that will take years to analyze and evaluate fully.Published by Copernicus Publications on behalf of the European Geosciences Union. L. T. Molina et al.: Mexico City emissions and their transport and transformationIn this paper we review over 120 papers resulting from the MILAGRO/INTEX-B Campaign that have been published or submitted, as well as relevant papers from the earlier MCMA-2003 Campaign, with the aim of providing a road map for the scientific community interested in understanding the emissions from a megacity such as the MCMA and their impacts on air quality and climate. This paper describes the measurements performed during MILAGRO and the results obtained on MCMA's atmospheric meteorology and dynamics, emissions of gases and fine particles, sources and concentrations of volatile organic compounds, urban and regional photochemistry, ambient particulate matter, aerosol radiative properties, urban plume characterization, and health studies. A summary of key findings from the field study is presented.

Elucidating severe urban haze formation in China

“…The combination of the enormously efficient aerosol nucleation and growth over an extended period (2−4 d or longer) yields a high mass concentration with numerous large particles during the severe PM 2.5 episodes in Beijing, uniquely different from those typically observed in other regions worldwide (7). On the other hand, the particle chemical compositions measured in Beijing are quite similar to those commonly measured in other global regions, consistent with the chemical constituents dominated by secondary aerosol formation (31,33). Photochemical oxidation of VOCs and NO x from urban traffic emissions and SO 2 from regional industrial sources is primarily responsible for the large secondary formation during the severe PM 2.5 events, but the contribution from primary emissions and regional transport of PM 2.5 is small.…”

“…Hence, our analysis of the aerosol chemical composition indicates dominant secondary aerosol constituents throughout the episodes, i.e., the nucleation mode particles containing mainly secondary organics and PM 2.5 during the polluted period consisting primarily of secondary organics, sulfate, nitrate, and ammonium. Interestingly, while the evolutions in the particle size distribution and mass concentration for the severe PM 2.5 episodes in Beijing are noticeably distinct, the aerosol chemical compositions measured by AMS in our study are similar to those commonly measured in other global urban regions (29,(31)(32)(33). For example, the mass fractions of organic, sulfate, and nitrate measured by AMS are typically 45%, 23%, and 18% in urban regions worldwide (29,(31)(32)(33), comparable to the values of 43%, 17%, and 22% averaged over our entire measurement period in Beijing (Fig.…”

NASA LaRC airborne high spectral resolution lidar aerosol measurements during MILAGRO: observations and validation

“…In this paper we present the NASA Langley airborne HSRL measurements from the MILAGRO field campaign (Molina et al, 2009). This campaign was designed to study the evolution of trace gases and aerosols above and downwind of Mexico City and employed ground-based instrumentation in and around the urban megacity along with numerous airborne instruments on seven aircraft.…”

PM1 Chemical Characterization during the ACU15 Campaign, South of Mexico City

“…The chemistry, and processes of the atmosphere in Mexico City have been broadly studied in two large campaigns: MCMA03 which occurred in April of 2003 [10], and MILAGRO (Megacity Initiative: Local And Global Research Observations) in March 2006 [11]. MCMA03 focused on mobile laboratory measurements, and on a highly instrumented "supersite" at the urban site CENICA (CEN) located east of the city.…”