GAW Report No. 205 - IGAC Project

CHAPTER 7 – OVERVIEW OF INTERNATIONAL COLLABORATIVE RESEARCH ACTIVITIEScomposition and climate. MIRAGE-Mex was led by the US National Center for AtmosphericResearch (NCAR) in collaboration with academic researchers under US-NSF sponsorship. The USNCAR/NSF C-130 aircraft sampled air above and at different distances from Mexico City tomeasure how gases and particles age during transport, specifically tracking the chemical, physical,and optical properties that have the potential to affect air quality, weather, and climate on largegeographic scales. The Twin Otter conducted studies of fire emissions and their effect on the localand regional composition of the atmosphere.4) INTEX-B (Intercontinental Chemical Transport Experiment-B) was an integrated fieldcampaign designed to understand the transport and transformation of gases and aerosols ontranscontinental/intercontinental scales and to assess their impact on air quality and climate.Central to achieving this goal was the need to relate space-based observations with those fromairborne and surface platforms. The NASA DC-8 was operated from Houston, Texas with researchflights over Mexico and the Gulf of MexicoThe measurement phase consisted of using wide-ranging meteorological, gas and aerosolsinstruments at ground sites and on aircraft and satellites. All of these platforms together can beused to trace the evolution of the urban plume as it merges with the regional backgroundatmosphere (Figure 8). Three supersites, spaced ~ 30 km apart, were set up to examine theevolution of the primary emitted gases and fine particles. The designations “T0” (initial time), “T1”(first time step), and “T2” (second time step) in Figure 9 refer to the timing of transport of the urbanplume to different points in space and time. Additional platforms in or near Mexico City includedmobile vans containing scientific laboratories and mobile and stationary lidars. Seven researchaircraft provided information about the atmosphere over a large region and at various altitudes.Satellite-based instruments provided even larger geographical coverage. The overall campaign wascomplemented by meteorological forecasting and numerical simulations, as well as an ambient airquality monitoring network operated by the Mexico City government and meteorologicalmeasurements were provided by the Mexican National Weather Service. Together, theseobservations provided a very comprehensive characterization of the MCMA’s urban and regionalatmospheric composition and chemistry that will require extensive analyses and use in modelimprovement to yield maximum benefits.Figure 8 - MILAGRO Campaign Geographic Coverage. Measurements were performed in the MCMA (see Figure 9). Thesize of the circle (MAX-Mex, MIRAGE-Mex and INTEX-B) indicates the geographic coverage of the aircraft deployed258