The spatial growth of individual contrails of commercial aircrafts in the time range from 1 min to 60 min behind the aircraft is investigated by means of a ground‐based scanning backscatter lidar. The growth in width varies between 18 m/min and 140 m/min, and the growth of the cross‐section between 3500 m²/min and 25000 m²/min. These values cover the findings of model calculations and former investigations. The vertical growth is often limited by boundaries of the humid layer at flight level, but values up to 18 m/min were observed. In a single case a vertical growth of 4.5 m/s during the early vortex regime was derived from video images.
By means of a scanning backscatter and depolarization lidar, contrails have been investigated for ages between a few seconds and 60 min. At environmental temperatures ≤−60°C the depolarization measured in the contrails rises from about 0.1 to 0.5 with time, whereas at higher temperatures around −50°C already the youngest contrails exhibit depolarization values of about 0.5. This indicates a strong dependence of the aerosol formation and growth on the environmental temperature which might influence their behavior in the atmosphere.
Three lidar systems at the northern hemisphere sites of Naha and Tsukuba, both in Japan, and Garmisch-Partenkirchen, Germany, have been observing the evolution, spread and decay of the aerosol cloud which had formed in the stratosphere after the explosive eruption of the Philippine volcano Pinatubo in mid-June 1991. Three years of lidar measurements show the depletion of the initial equatorial aerosol reservoir and the subsequent transport to the north. These lidar data are the basis for the calculation of the climatically relevant parameters aerosol optical depth, mass and surface area
Abstract. Air traffic is a source of trace gases in the upper troposphere and lower stratosphere. Contrails readily form from water vapor exhausts under favorable meteorological conditions. Since contrails are ice crystal clouds like natural cirrus clouds, they bear a greenhouse potential which has to be investigated. The IFU has built a scanning lidar system employing a pulsed Nd:YAG laser as the emitter and a 52-cm diameter telescope as the receiver. Signals are processed in several channels to investigate depolarization and wavelength dependencies of the light backscattered from ice crystals. These investigations are aimed at the formation and life cycles of contrails, their optical properties, and their climatological consequences in areas of dense air traffic. The experimental lidar setup is described and a sample measurement is shown.
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