HR: 0830h
AN: A51D-0715    [PDF]
TI: Measurements of HNO$_3$ on the NOAA Research Vessel Ronald H. Brown During NEAQS 2002
AU: Dibb, J E
EM: jack.dibb@unh.edu
AF: Climate Change Research Center, Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH 03824 United States
AU: Scheuer, E
AF: Climate Change Research Center, Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH 03824 United States
AU: Whitlow, S I
AF: Climate Change Research Center, Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH 03824 United States
AU: Vozella, M
AF: Climate Change Research Center, Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH 03824 United States
AU: * Talbot, R W
AF: Climate Change Research Center, Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH 03824 United States
AB: Nitric acid was measured at 5 minute resolution with an automated mist chamber/ion chromatograph sampling/analysis system. More than 3000 measurements were made from 29 July through 10 August, 2002, mainly in the Gulf of Maine but also during the transect to South Carolina at the end of the cruise. Mixing ratios of HNO$_3$ varied over a wide range from day to day in response to synoptic conditions, with southeasterly flow bringing much cleaner air to the sampling region on several days. The maximum mixing ratio (7.1 ppbv) was observed in Boston Harbor, but the prevailing westerly flow carried regionally polluted air masses to the ship for most of the study, resulting in an overall mean HNO$_3$ mixing ratio of 1.1 ppbv. Pronounced diurnal variability was superimposed on these synoptic changes. Peak mixing ratios were observed each day around solar noon (mean for the interval 11:00 - 15:00 local time was 2.01 ppbv), with minima near sunrise and sunset. The morning hours between 6:00 - 8:00 almost always had the lowest HNO$_3$ mixing ratios each day, overall the mean during this period was 0.57 ppb. Interestingly, nitric acid increased after dark to a secondary maximum, averaging 0.98 ppbv for the 4 hours centered around midnight. The nighttime peak of HNO$_3$ was generally much broader than the daily maximum in the early afternoon, suggesting sustained production of HNO$_3$ in the dark (see Brown et al., this session).
DE: 0345 Pollution--urban and regional (0305)
DE: 0365 Troposphere--composition and chemistry
DE: 0368 Troposphere--constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting