eas6792 air pollution meteorology
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Transcript of eas6792 air pollution meteorology
eas6792eas6792air pollution meteorologyair pollution meteorology
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Diurnal vertical concentration Diurnal vertical concentration profile of CO in an urban profile of CO in an urban
environmentenvironment
byby
BurBurççak Kaynakak Kaynak
IntroductionIntroductionAir quality in urban areas
connection between air pollution and human health emissions and concentrations of primary pollutants
shows extremely strong spatial and temporal variations
characterization of urban air pollution is fairly complicated
CO and other pollutants may concur in several chemical processes,
contributing to the formation of other pollutants (o3)
have injurious effects on the health damage vegetation and materials, alter temperature and wind distribution,
generally affect urban climates
IntroductionIntroduction
Concentrations of pollutants in urban areas balance between pollutant accumulation and dispersion
Strong gradients of gaseous and particulate pollutants (in the vertical and horizontal direction) mainly due to
activities of emission sources rapid mixing dilution of emissions
CO is a good indicator to understand the dispersion and advection processes in the urban areas
IntroductionIntroductionThe diurnal vertical profile of CO in a suburban area will be calculated by Euler explicit method and compared with the actual measurements
assumptions:velocity (u) and eddy diffusion coefficient (Kz) profiles for typical urban atmospherediurnal emission profiles of CO, scaled according to the max. emissionsboundary layer heights for 2 cases: day time(1200m), night time (200m)no sources or sinks (long lifetime of CO)
Measurements for Measurements for comparisoncomparison
“Wintertime vertical profiles of air pollutants over a suburban area in central
Taiwan” (Chen et al., 2002.)
Vertical CO profiles through 1200 m
Assumptions_Assumptions_input datainput data
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Measurements_Measurements_CO diurnal CO diurnal profilesprofiles
Measurements_Measurements_CO vertical CO vertical profilesprofiles
System equationSystem equationδC/δt = Kz(z)*δ2C/δz2 +u(z)*(Co-C)/ δz
By using Taylor series, at steady state
0 = Kz(z)[ C(z+Δz)-2 C(z)+ C(z-Δz)]/ Δz2 + (u(z)C(z))/Δz
say C(z+Δz) =Ci+1C(z) =CiC(z-Δz) =Ci-1
0 = Kz i[ Ci+1 - 2Ci + Ci-1]/ Δz2 + (u i Ci)/Δz
So Ci+1 = [ 2Ci - Ci-1] - (u i Ci)*Δz/Kz i
Findings_Findings_vertical profile for day vertical profile for day @[email protected].
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CO (ppm)
z (m
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disp. without u
u addition
2 nd disp.
Expected outcomesExpected outcomesthe average vertical profile of vehicular pollutant conc.s the general exponential form (rather than simple exponential function or Gaussian distribution)
Maximums morning hours w/ relatively high traffic and low mixing
Good correlation between traffic load and mechanical mixing
Decreasing CO concentrations with height
ProblemsProblems
The concentrations are going to “zero” or “-” values immediately
Possible reasons could be:The explicit method is unstableThe velocities assumed are too high that they swept all the COProblems in writing the algorithm or in coding in the Mathlab program
Future workFuture work
Finding the problems in the solutionObtaining a reasonable vertical profileComparison of the day and night profilesEffect of the traffic emission loads on vertical profilesComparison of the numerical solution with the measurements in the reference noted
Thanks for listening…any questions ???