Low temperature inversion seen from balloon

The photo is from a balloon flight carried out to measure ozone and NO2 aloft. The flight started soon after sunrise and lasted for about 2 hours. A temperature inversion is clearly seen in the horizon; pollutants trapped below cause the brownish colour of the air below the inversion. The ballon was at an altitude of about 2 km when this photo was taken; this is probably also the approximate height of the inversion, as it was best seen from this altitude.