Diurnal characteristics of surface level O3 and other important trace gases in New England -: art. no. D09307

[1] Data obtained from spring 2001 to summer 2003 in New England by the Atmospheric Investigation, Regional Modeling, Analysis and Prediction (AIRMAP) program were used to document the diurnal characteristics of O-3, CO2, NO, and during selected intervals hydrocarbon and oxygenated species. The diurnal cycles of O-3 and oxygenated species showed a monotonic rise in mixing ratio following sunrise ( replenishment) that was mirrored by nighttime removal ( depletion) under the nocturnal inversion. The median depletion rate of O-3 was 4.9 ppbv h(-1) compared to a replenishment rate of 6.2 ppbv h(-1). The significant and rapid loss of O-3 at night combined with an anthropogenic hydrocarbon signature dominated by a vehicular source led us to the hypothesis that nocturnal O-3 depletion represented the combined effects of dry deposition and titration by NO released from mobile sources. Nighttime removal of O-3 averaged 31 ppbv ( median of 27 ppbv), with similar to 11 ppbv due to dry deposition and similar to 20 ppbv loss by titration with NO and NO2. The seasonally averaged diurnal cycles of O-3 and NO were very similar from year to year, indicating that although there was large variability in the daily levels of these species, their sources/sinks were quite consistent. Moreover, CO2 and selected hydrocarbons exhibited a diurnal cycle opposite to that of O-3, with the highest mixing ratios occurring at night. The diurnal cycles of oxygenated compounds such as methanol, acetaldehyde, methyl ethyl ketone, acetone + propanal, methyl vinyl ketone + methacrolein were investigated for a 2 day time period in July 2003. Our data are among the first to illustrate the diurnal cycle of these compounds. We used these species to demonstrate the importance of vertical mixing in driving the diurnal cycle of ground level O-3 in New England. Day/night ratios ranged from 2.3 for acetone + propanal to 11 for methyl vinyl ketone + methacrolein. Deposition velocities of 0.5- 1 m s(-1) were estimated for these species, which are significantly higher than values used in many models. Such efficient removal may have important implications for the chemical impact of these species, at least on a regional scale.