Evaluation of Vertical Fluxes of Nitrogen Oxide to the Troposphere from the Wide Land Surfaces

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The vertical fluxes of nitrogen oxide (NOX) including nitrogen dioxide (NO2) and nitrogen mono-oxide (NO) to the troposphere from the wide land surfaces in Miyagi Prefecture and the neighborhood areas have been hourly estimated during 8 years (1991-1998). The fundamental studies were composed of the experimental observations of NOX vertical profiles, the theoretical analyses and the researches of vertical static stabilities in the urban area. The vertical profiles of NOX were measured at the main street of 27 m-width in the urban area of Sendai City. The volumetric summations NOX of NO2 and NO are conserved in the urban canopy layer and the vertical profiles of NOX in the street canyon were clarified to have two layers by the measurements and the theoretical studies of turbulent transfers of NOX. The vertical profiles of NOX density in the upper layer have a logarithmic shape being represented by the nearly first-order equation of Inz where z is the height from the road surface. In the … More lower layer the density of NOX is nearly constant independent of the height. The transitional height of the logarithmic layer and the constant layer is about z=1〜2 m. The theory of vertical transfer of NOX were formulated. The estimation methods of friction NOX-density were introduced and the values of friction NOX-density were calculated from the data of the routine NOX-observatories controlled by the government and the prefectures. The friction velocities and the static stability were calculated from the observational data of official meteorological observatories by use of the new theoretical heat-budget model improved in the present research project in which the differences between urban canopy and the urban canyon and the roles of snowfall and the snow cover are considered. The vertical fluxes of NOX were hourly calculated with the values of the friction NOX-density and the friction velocity.The averaged fluxes transformed into NO2 mass during 8 years were 625 kg per one year and per the road area of 27 m X 100 m at the roads considered as the source site of NOX and the averaged values were decreased in about one third of those at the roads in the urban area being far away from the roads. Less