HR: 0830h
AN: A51E-0727 [PDF]
TI: Vertical Concentration Profiles of Nitrous Acid in the Boundary Layer: Comparison of Observations and
1D Modeling Results
AU: * Stutz, J
EM: jochen@atmos.ucla.edu
AF: University of California Los Angeles, Dept. Atmospheric Sciences, 7127 Math Sciences, Los Angeles, CA
90095-1565 United States
AU: Geyer, A
EM: andreas@atmos.ucla.edu
AF: University of California Los Angeles, Dept. Atmospheric Sciences, 7127 Math Sciences, Los Angeles, CA
90095-1565 United States
AU: Wang, S
EM: shw@atmos.ucla.edu
AF: University of California Los Angeles, Dept. Atmospheric Sciences, 7127 Math Sciences, Los Angeles, CA
90095-1565 United States
AB:
Nitrous acid, HONO, is an important precursor for OH radicals in the polluted atmosphere. HONO accumulates in the nocturnal
boundary layer (NBL) and its photolysis at sunrise is often the dominant OH source at the ground. Although it is well known
that HONO is formed by the heterogeneous conversion of NO$_2$, the surfaces involved in this process have not been clearly
identified. The concentrations of HONO also depend strongly on the stability of the NBL. Many of the uncertainties about HONO
formation in the atmosphere originate in the poorly understood role of the various urban surfaces and the influence of
vertical mixing, which can lead to strong vertical concentration gradients of both HONO and NO$_2$.
In recent years we have performed several field experiments to study the NO$_2$ - HONO system in the polluted boundary layer
(e.g. TEXAQS, 2000, NEAQS/NAOPEX, 2002). In all studies we measured vertical concentration profiles of NO$_2$, HONO, and
various other trace gases in the boundary layer by Differential Optical Absorption Spectroscopy continuously throughout the
night and the following morning. Here we present a comprehensive analysis of the vertical distribution of NO$_2$ and HONO in
these urban environments. The observations will be compared with results from a one-dimensional chemical transport model in
order to investigate the influence of the ground, building surfaces, and aerosol on the formation of HONO. The altitude
dependence of the early morning OH formation will also be discussed.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
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