Atmospheric humidity and temperature data can predict contrail formation over a location
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Peer-reviewed literature demonstrates that atmospheric temperature and humidity data, via meteorological models like ERA5, are utilized to estimate and predict contrail formation.
Abstract. Aviation contributes to global emissions of carbon dioxide, aerosol particles, water vapor (WV), and other compounds. WV promotes the formation of condensation trails (contrails), which are known for their net warming effect on the climate. Contrail formation is often estimated using the Schmidt–Appleman criterion (SAc) together with meteorological data from the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5 atmospheric reanalysis model. We compare ERA5 output of temperature and relative humidity in the upper troposphere and lower stratosphere with 5 years of In-service Aircraft for a Global Observing System (IAGOS) observations over the North Atlantic. Good agreement was found for the temperature fields, with a maximum bias of −0.4 K (200 hPa level), while larger biases were found for relative humidity of up to −5.5 % (250 hPa level). Using original ERA5 data, conditions prone to contrail formation occurred 50.3 % and 7.9 % of the time for non-persistent and persistent contrails, respectively, while 44.0 % and 12.1 % were flagged in the IAGOS data. We propose a multivariate quantile mapping (QM) correction to remove systematic biases by post-processing ERA5 temperature and relative humidity fields with respect to contrail formation. The QM correction was applied to post-process ERA5 data, reducing the temperature bias to less than 0.1 K and the relative humidity bias to less than −1.5 %, resulting in 44 % and 10.9 % of the data points now being flagged for non-persistent and persistent contrail formation, respectively. Our bias correction generalizes well compared to the IAGOS observations. How it generalizes outside the IAGOS regions remains to be investigated.
is determined by the air temperature, atmospheric pressure, and ice supersaturation (the amount by which the relative humidity exceeds 100%). Cirrus in
Cirrus (cloud classification symbol: Ci) is a genus of high-altitude cloud made of ice crystals. Cirrus clouds typically appear delicate and wispy with white strands. In the Earth's atmosphere, cirrus are usually formed when warm, dry air rises, causing water vapor deposition onto mineral dust and metallic particles at high altitudes. Globally, they form anywhere between 6,000 and 20,000 meters (2
Scientists have studied the properties of cirrus using several different methods. Lidar (laser-based radar) gives highly accurate information on the cloud's altitude, length, and width. Balloon-carried hygrometers measure the humidity of the cirrus cloud but are not accurate enough to measure the depth of the cloud. Radar units give information on the altitudes and thicknesses of cirrus clouds. Another data source is satellite measurements from the Stratospheric Aerosol and Gas Experiment program. These satellites measure where infrared radiation is absorbed in the atmosphere, and if it is absorbed at cirrus altitudes, then it is assumed that there are cirrus clouds in that location. NASA's Moderate-Resolution Imaging Spectroradiometer gives information on the cirrus cloud cover by measuring reflected infrared radiation of various specific frequencies during the day. During the night, it determines cirrus cover by detecting the Earth's infrared emissions. The cloud reflects this radiation back to the ground, thus enabling satellites to see the "shadow" it casts into space. Visual observations from aircraft or the ground provide additional information about cirrus clouds. Particle Analysis by Laser Mass Spectrometry (PALMS) is used to identify the type of nucleation seeds that spawned the ice crystals in a cirrus cloud.
Cirrus clouds have an average ice crystal concentration of 300,000 ice crystals per 10 cubic meters (270,000 ice crystals per 10 cubic yards). The concentration ranges from as low as 1 ice crystal per 10 cubic meters to as high as 100 million ice crystals per 10 cubic meters (just under 1 ice crystal per 10 cubic yards to 77 million ice crystals per 10 cubic yards), a difference of eight orders of magnitude. The size of each ice crystal is typically 0.25 millimeters, but they range from as short as 0.01 millimeters up to several millimeters. The ice crystals in contrails can be much smaller than those in naturally occurring cirrus cloud, being around 0.001 millimeters to 0.1 millimeters in length.
In addition to forming in different sizes, the ice crystals in cirrus clouds can crystallize in different shapes: solid columns, hollow columns,…
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