Vertical profiles of NO3, N2O5, O3, and NOxin the nocturnal boundary layer: 2. Model studies on the altitude dependence of composition and chemistry

2004 ◽  
Vol 109 (D12) ◽  
Author(s):  
Andreas Geyer
Keyword(s):  
Boundary Layer ◽  
Nocturnal Boundary Layer ◽  
Vertical Profiles ◽  
Model Studies ◽  
Altitude Dependence ◽  
Layer 2

scholarly journals Vertical profiles of O<sub>3</sub> and NO<sub>x</sub> chemistry in the polluted nocturnal boundary layer in Phoenix, AZ: I. Field observations by long-path DOAS

2006 ◽  
Vol 6 (9) ◽  
pp. 2671-2693 ◽  
Author(s):  
S. Wang ◽  
R. Ackermann ◽  
J. Stutz
Keyword(s):  
Boundary Layer ◽  
Urban Areas ◽  
Dominant Role ◽  
Vertical Mixing ◽  
Nocturnal Boundary Layer ◽  
Trace Gas ◽  
Vertical Profiles ◽  
Chemical Production ◽  
Reactive Trace Gases ◽  
Vertical Gradients

Abstract. Nocturnal chemistry in the atmospheric boundary layer plays a key role in determining the initial chemical conditions for photochemistry during the following morning as well as influencing the budgets of O3 and NO2. Despite its importance, chemistry in the nocturnal boundary layer (NBL), especially in heavily polluted urban areas, has received little attention so far, which greatly limits the current understanding of the processes involved. In particular, the influence of vertical mixing on chemical processes gives rise to complex vertical profiles of various reactive trace gases and makes nocturnal chemistry altitude-dependent. The processing of pollutants is thus driven by a complicated, and not well quantified, interplay between chemistry and vertical mixing. In order to gain a better understanding of the altitude-dependent nocturnal chemistry in the polluted urban environment, a field study was carried out in the downtown area of Phoenix, AZ, in summer 2001. Vertical profiles of reactive species, such as O3, NO2, and NO3, were observed in the lowest 140 m of the troposphere throughout the night. The disappearance of these trace gas vertical gradients during the morning coincided with the morning transition from a stable NBL to a well-mixed convective layer. The vertical gradients of trace gas levels were found to be dependent on both surface NOx emission strength and the vertical stability of the NBL. The vertical gradients of Ox, the sum of O3 and NO2, were found to be much smaller than those of O3 and NO2, revealing the dominant role of NO emissions followed by the O3+NO reaction for the altitude-dependence of nocturnal chemistry in urban areas. Dry deposition, direct emissions, and other chemical production pathways of NO2 also play a role for the Ox distribution. Strong positive vertical gradients of NO3, that are predominantly determined by NO3 loss near the ground, were observed. The vertical profiles of NO3 and the calculated vertical profiles of its reservoir species (N2O5) confirm earlier model results suggesting complex vertical distributions of atmospheric denoxification processes during the night.

scholarly journals Biogenic VOC oxidation and organic aerosol formation in an urban nocturnal boundary layer: aircraft vertical profiles in Houston, TX

2013 ◽  
Vol 13 (5) ◽  
pp. 11863-11918
Author(s):  
S. S. Brown ◽  
W. P. Dubé ◽  
R. Bahreini ◽  
A. M. Middlebrook ◽  
C. A. Brock ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Nitrogen Oxides ◽  
Model Simulation ◽  
Field Measurements ◽  
Organic Aerosol ◽  
Nocturnal Boundary Layer ◽  
Vertical Profiles ◽  
Biogenic Hydrocarbons ◽  
Aerosol Formation ◽  
Aerosol Composition

Abstract. Organic compounds are a large component of aerosol mass, but organic aerosol (OA) sources remain poorly characterized. Recent model studies have suggested nighttime oxidation of biogenic hydrocarbons as a potentially large OA source, but analysis of field measurements to test these predictions is sparse. We present nighttime vertical profiles of nitrogen oxides, ozone, VOCs and aerosol composition measured during low approaches of the NOAA P-3 aircraft to airfields in Houston, TX. This region has large emissions of both biogenic hydrocarbons and nitrogen oxides. The latter serves as a source of the nitrate radical, NO3, a key nighttime oxidant. Biogenic VOCs (BVOC) and urban pollutants were concentrated within the nocturnal boundary layer (NBL), which varied in depth from 100–400 m. Despite concentrated NOx at low altitude, ozone was never titrated to zero, resulting in rapid NO3 radical production rates of 0.2–2.7ppbv h-1 within the NBL. Monoterpenes and isoprene were frequently present within the NBL and underwent rapid oxidation (up to 1ppbv h−1), mainly by NO3 and to a lesser extent O3. Concurrent enhancement in organic and nitrate aerosol on several profiles was consistent with primary emissions and with secondary production from nighttime BVOC oxidation, with the latter equivalent to or slightly larger than the former. Ratios of organic aerosol to CO within the NBL ranged from 14 to 38 μg m−3 OA/ppmv CO. A box model simulation incorporating monoterpene emissions, oxidant formation rates and monoterpene SOA yields suggested overnight OA production of 0.5 to 9 μg m−3.

scholarly journals Biogenic VOC oxidation and organic aerosol formation in an urban nocturnal boundary layer: aircraft vertical profiles in Houston, TX

2013 ◽  
Vol 13 (22) ◽  
pp. 11317-11337 ◽  
Author(s):  
S. S. Brown ◽  
W. P. Dubé ◽  
R. Bahreini ◽  
A. M. Middlebrook ◽  
C. A. Brock ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Nitrogen Oxides ◽  
Model Simulation ◽  
Field Measurements ◽  
Organic Aerosol ◽  
Nocturnal Boundary Layer ◽  
Vertical Profiles ◽  
Biogenic Hydrocarbons ◽  
Aerosol Formation ◽  
Aerosol Composition

Abstract. Organic compounds are a large component of aerosol mass, but organic aerosol (OA) sources remain poorly characterized. Recent model studies have suggested nighttime oxidation of biogenic hydrocarbons as a potentially large OA source, but analysis of field measurements to test these predictions is sparse. We present nighttime vertical profiles of nitrogen oxides, ozone, VOCs and aerosol composition measured during low approaches of the NOAA P-3 aircraft to airfields in Houston, TX. This region has large emissions of both biogenic hydrocarbons and nitrogen oxides. The latter category serves as a source of the nitrate radical, NO3, a key nighttime oxidant. Biogenic VOCs (BVOC) and urban pollutants were concentrated within the nocturnal boundary layer (NBL), which varied in depth from 100–400 m. Despite concentrated NOx at low altitude, ozone was never titrated to zero, resulting in rapid NO3 radical production rates of 0.2–2.7 ppbv h−1 within the NBL. Monoterpenes and isoprene were frequently present within the NBL and underwent rapid oxidation (up to 1 ppbv h−1), mainly by NO3 and to a lesser extent O3. Concurrent enhancement in organic and nitrate aerosol on several profiles was consistent with primary emissions and with secondary production from nighttime BVOC oxidation, with the latter equivalent to or slightly larger than the former. Some profiles may have been influenced by biomass burning sources as well, making quantitative attribution of organic aerosol sources difficult. Ratios of organic aerosol to CO within the NBL ranged from 14 to 38 μg m−3 OA/ppmv CO. A box model simulation incorporating monoterpene emissions, oxidant formation rates and monoterpene SOA yields suggested overnight OA production of 0.5 to 9 μg m−3.

scholarly journals Vertical profiles of NO<sub>x</sub> chemistry in the polluted nocturnal boundary layer in Phoenix, AZ: I. Field observations by long-path DOAS

2006 ◽  
Vol 6 (1) ◽  
pp. 45-106
Author(s):  
S. Wang ◽  
R. Ackermann ◽  
J. Stutz
Keyword(s):  
Boundary Layer ◽  
Urban Areas ◽  
Dominant Role ◽  
Vertical Mixing ◽  
Nocturnal Boundary Layer ◽  
Trace Gas ◽  
Vertical Profiles ◽  
Chemical Production ◽  
Reactive Trace Gases ◽  
Vertical Gradients

Abstract. Nocturnal chemistry in the atmospheric boundary layer plays a key role in determining the initial chemical conditions for photochemistry during the following morning as well as influencing the budgets of O3 and NO2. Despite its importance, chemistry in the nocturnal boundary layer (NBL), especially in heavily polluted urban areas, has received little attention so far, which greatly limits the current understanding of the processes involved. In particular, the influence of vertical mixing on chemical processes gives rise to complex vertical profiles of various reactive trace gases and makes nocturnal chemistry altitude-dependent. The processing of pollutants is thus driven by a complicated, and not well quantified, interplay between chemistry and vertical mixing. In order to gain a better understanding of the altitude-dependent nocturnal chemistry in the polluted urban environment, a field study was carried out in the downtown area of Phoenix, AZ, in summer 2001. Vertical profiles of reactive species, such as O3, NO2, and NO3, were observed in the lowest 140 m of the troposphere throughout the night. The disappearance of these trace gas vertical profiles during the morning coincided with the morning transition from a stable NBL to a well-mixed convective layer. The vertical gradients of trace gas levels were found to be dependent on both surface NOx emission strength and the vertical stability of the NBL. The vertical gradients of Ox, the sum of O3 and NO2, were found to be much smaller than those of O3 and NO2, revealing the dominant role of NO emissions followed by the O3+NO reaction for the altitude-dependence of nocturnal chemistry in urban areas. Dry deposition, direct emissions, and other chemical production pathways of NO2 also play a role for the Ox distribution. Strong positive vertical gradients of NO3, that are predominantly determined by NO3 loss near the ground, were observed. The vertical profiles of NO3 and its reservoir species (N2O5) confirm earlier model results suggesting complex vertical distributions of atmospheric denoxification processes during the night.

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