Tuesday, 15 January 2002: 9:15 AM
The Phoenix 2001 field campaign: evolution of oxidants during the morning transition period
A field experiment was conducted in Phoenix, AZ during June 2000 to study the accumulation of ozone precursors and other pollutants in the stable nocturnal boundary layer and to investigate the subsequent breakup of this layer and the evolution of the air chemistry in the lowest kilometer of the atmosphere during the morning hours. Instruments to measure O3, NO, NOy, CO, PAN, and VOCs were located on the 16th and 39th floor of a building in downtown Phoenix, and near-surface measurements of O3, NO, NO2, NOx, and CO were available from a site near the building. Additional information on the vertical distributions of O3, SO2, NO2, HCHO, HONO, and NO3 was available from a dual optical absorption spectrometer mounted at the 39th floor that sampled multiple paths using an array of three retroreflectors mounted on other buildings in the downtown area. A Gulfstream-1 airplane made repeated passes over the downtown region and areas to the west at heights ranging from 400 to 700 m above the surface between approximately 0730 and 1015 LST on 12 days. The airplane measured O3, NO, NOy, CO, and VOCs; in combination with the surface and building measurements, these flights allowed sampling of the boundary layer chemistry from the surface to near and above the top of the developing mixed layer during the morning transition hours. Detailed meteorological information was collected from an array of 3 radar wind profilers with radio acoustic sounding systems for virtual temperature measurements, 4 sodars, up to 15 radiosondes per day released from two sites - one near the downtown area and one in a more rural area to the west, a tethered balloon, 6 surface meteorological stations, and 41 temperature data loggers. Ozone profiles were also obtained from a second tethered balloon and from ozonesondes launched twice a day. An overview of the experimental arrangement and operating procedures is given, and examples of the development of the boundary layer and its effects on the vertical profiles of trace species concentrations is provided.