Contrail life cycle and properties from one year of MSG/SEVIRI rapid-scan images
The Automatic Contrail Tracking Algorithm (ACTA) -developed to automatically follow contrails as they age, drift and spread- enables the study of a large number of contrails and the evolution of contrail properties with time. In this paper we present a year's worth of tracked contrails, from August 2008 to July 2009 in order to derive statistically significant mean values. The tracking is performed using the 5 min rapid-scan mode of the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on board of the Meteosat Second Generation satellites (MSG). The detection is based on the high spatial resolution of the images provided by the Moderate Resolution Imaging Spectroradiometer on board of the Terra satellite (Terra/MODIS), where a Contrail Detection Algorithm (CDA) is applied. The results show the satellite-derived average lifetimes of contrails and contrail-cirrus along with the probability density function (PDF) of other geometric characteristics such as mean coverage, distribution and width. In combination with specifically developed algorithms (RRUMS and COCS, explained below) it is possible to derive the radiative forcing (RF), energy forcing (EF), optical thickness (τ), and altitude of the tracked contrails. Mean values here retrieved are: duration, 1 h; length, 130 km; width, 8 km; altitude, 11.7 km; optical thickness, 0.34. Radiative forcing and energy forcing are shown for land/water backgrounds in day/night situations.