Observations of NOx, ΣPNs, ΣANs, and HNO3 at a rural site in the California Sierra Nevada Mountains: summertime diurnal cycles
1Department of Chemistry, University of California, Berkeley, CA, USA
2Department of Environmental Science, Policy and Management, University of California, Berkeley, CA, USA
3Department of Earth and Planetary Science, University of California, Berkeley, CA, USA
*now at: Scripps Institution of Oceanography, Univ. of California, San Diego, La Jolla, USA
**now at: Cooperative Institute for Research in Environmental Science (CIRES), University of Colorado, Boulder, CO, USA
Abstract. Observations of NO, NO2, total peroxy nitrates (ΣPNs), total alkyl nitrates (ΣANs), HNO3, CO, O3, and meteorological parameters were obtained from October 2000 through February 2002 at 1315 m a.s.l., 38.97° N, 120.6° W on Sierra Pacific Industries land, adjacent to the University of California Blodgett Forest Research Station (UC-BFRS). We describe the data set with emphasis on the diurnal cycles during summertime 2001. We show that transport of the Sacramento urban plume is a primary factor responsible for diurnal variation in total reactive nitrogen mixing ratios as well as in NOx, ΣPNs and ΣANs, all of which exhibit a late afternoon/early evening peak. In contrast, HNO3 has a peak just after local noon indicating that HNO3 is in near steady state during the day with production due to photochemistry and removal by deposition and mixing with the background free troposphere. Boundary layer dynamics influence mixing ratios of all species in the early morning. Analysis of the morning feature suggests that higher mixing ratios of NOx and HNO3 persist in the residual layer than in the nocturnal boundary layer indicating the presence of nocturnal sinks of both species. Nighttime observations also indicate large HNO3 and ΣANs production through oxidation of alkenes by NO3.