Ozone and nitrogen dioxide absorption at twilight
This is a focus on the deep twilight spectra of the clear sky in the UV and blue regions of the spectra shown in the previous two plots. The shallow broad depression over the wavelength range from 350–450nm is due to the absorption of nitrogen dioxide, most probably originating from vehicle exhaust in the southern part of Bath. The computed transmission spectrum of a column of 2 x 10^17 NO_2 molecules per sq cm is shown as the red line (100% transmission is at a y-axis value of 2.5e-3).
This column density has not been scaled to fit the data but it illustrates the broad dip around 400nm and the stronger narrow spectral features are correlated with the structure in the observed spectrum: the Maya has too low a spectral resolution to see these features clearly.
The ozone transmission (green line) has also been computed, using a column of 4 x 10^19 O_3 molecules per sq cm. This shows part of the Huggins band on the left and the blue wing of the Chappuis band on the right. Again, the spectrometer does not fully resolve the fine structure of the band.
The overall slope, clearly apparent from 350–450nm, in the measured data is due to the combined effects or Rayleigh and aerosol scattering.
Ozone and nitrogen dioxide absorption at twilight
This is a focus on the deep twilight spectra of the clear sky in the UV and blue regions of the spectra shown in the previous two plots. The shallow broad depression over the wavelength range from 350–450nm is due to the absorption of nitrogen dioxide, most probably originating from vehicle exhaust in the southern part of Bath. The computed transmission spectrum of a column of 2 x 10^17 NO_2 molecules per sq cm is shown as the red line (100% transmission is at a y-axis value of 2.5e-3).
This column density has not been scaled to fit the data but it illustrates the broad dip around 400nm and the stronger narrow spectral features are correlated with the structure in the observed spectrum: the Maya has too low a spectral resolution to see these features clearly.
The ozone transmission (green line) has also been computed, using a column of 4 x 10^19 O_3 molecules per sq cm. This shows part of the Huggins band on the left and the blue wing of the Chappuis band on the right. Again, the spectrometer does not fully resolve the fine structure of the band.
The overall slope, clearly apparent from 350–450nm, in the measured data is due to the combined effects or Rayleigh and aerosol scattering.