Open AccessVertical profiles of NO 3 , N 2 O 5 , O 3 , and NO x in the nocturnal boundary layer: 1. Observations during the Texas Air Quality Study 2000
Author(s) -
Stutz Jochen,
Alicke Björn,
Ackermann Ralf,
Geyer Andreas,
White Allen,
Williams Eric
Publication year - 2004
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2003jd004209
Subject(s) - trace gas , differential optical absorption spectroscopy , altitude (triangle) , mixing ratio , deposition (geology) , atmospheric sciences , atmospheric chemistry , atmosphere (unit) , aerosol , chemical composition , planetary boundary layer , boundary layer , troposphere , chemistry , environmental science , absorption (acoustics) , ozone , meteorology , physics , geology , geometry , geomorphology , thermodynamics , optics , mathematics , organic chemistry , sediment
Nocturnal chemistry in urban areas can considerably influence the composition of the boundary layer by removing nitrogen oxides and hydrocarbons, as well as changing the size and composition of aerosol particles. Although these processes can have a severe impact on pollution levels at night and during the following day, little quantitative information is available. In particular, the vertical variation of trace gas concentrations and chemistry at night has received little attention and is thus poorly understood. Here we present differential optical absorption spectroscopy (DOAS) measurements of the vertical distributions of O 3 , NO 2 , and NO 3 during the Texas Air Quality Study 2000 near Houston, TX. Distinct vertical profiles, with lower mixing ratios of O 3 and NO 3 near the ground than above 100 m altitude, were observed. Mixing ratios of NO 3 aloft reached 50 ppt and above, and steady state N 2 O 5 levels were calculated to be 100–300 ppt. A one‐dimensional chemical transport model reveals that the formation of the vertical trace gas distributions is driven by deposition, surface emissions of NO, reactions of O 3 and NO 3 , and vertical mixing. The removal of O 3 in Houston is found to proceed by dry deposition, while NO x is primarily lost above 10 m altitude by N 2 O 5 chemistry. The study shows that chemistry in polluted areas is strongly altitude dependent in the lowest 100 m of the nocturnal atmosphere. This altitude dependence should be considered in future field and model studies of urban air pollution.