Using Surveillance Flight Track Data and Terrestrial Sky Imaging to Record Airspace Contrail Statistics: the Washington D.C. Airspace

The United Nations International Panel for Climate Change (IPCC) attributes 2% of the Earth’s total anthropogenic climate change to Aircraft Induced Clouds (also known as Contrails). Contrails, produced when water vapor and soot, emitted by jet form cirrus-like clouds, reflect back to Earth outgoing "thermal" radiation that would otherwise leave the atmosphere for space, thus resulting in global heating. Researchers have proposed mitigations including navigational avoidance that requires flights to avoid the airspaces in which the atmospheric conditions are conducive to the formation of contrails. The current accuracy of the forecasts for the relative humidity of the atmosphere are considered insufficient to meet the accuracy requirements to perform navigational avoidance.This paper describes the first of several incremental steps to improve the forecast of atmospheric conditions for the purpose of contrail prediction and contrail avoidance. This paper describes the results of the analysis of terrestrial sky images for six months for the airspace over the Washington D.C. region. An average of 594 flights per day transited the airspace above FL320. Twenty-nine percent (34%) of the days had at least one hour with (natural) cirrus clouds, and 13% of the total daylight hours had (natural) cirrus clouds. One in every 67 flights in the airspace above FL 320 generated a long-lived contrail. This confirms that only a small number of flights would need a cruise flight level adjustment to avoid generating a contrail. The implications of these results, limitations of the study, and future work are discussed.