Study of aerosols in the atmosphere by twilight scattering
Photometric measurements of the light scattered from the twilight sky in the direction of the sun’s vertical at an angle of 70° from the zenith, were made during IGY-IGC (1957–59) at Mt. Abu with a photometer the telescope of which covered a circular field of about 1 degree.
Observations showed that there were changes in the slopes of the curves of intensity against the depression θ of the sun below the horizon, when θ was 5–6°. This could be explained by assuming the existence of an aerosol layer at 20–25 km. The height of the layer could however vary from 15 to 30 km.
The lowest heights of the stratospheric aerosol layer at Abu were found to occur in June and the highest in November–December.
A second feebler maximum corresponding to a scattering layer at a height of 45–50 km. was also found on a number of occasions.
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