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Preprints
https://doi.org/10.5194/egusphere-2024-2142
https://doi.org/10.5194/egusphere-2024-2142
16 Sep 2024
 | 16 Sep 2024

Influence of Temperature and Humidity on Contrail Formation Regions in EMAC: A Spring Case Study

Patrick Peter, Sigrun Matthes, Christine Frömming, Patrick Jöckel, Luca Bugliaro, Andreas Giez, Martina Krämer, and Volker Grewe

Abstract. While carbon dioxide emissions from aviation often dominate climate change discussions, the significant impact of non-CO2 effects like contrails and contrail-cirrus must not be overlooked, particularly for the mitigation of climate effects. This study evaluates key atmospheric parameters influencing contrail formation, specifically temperature and humidity, using various model setups of a general circulation model (GCM) with different vertical resolutions and two nudging methods for specified dynamics setups. Comparing simulation results with reanalysis data for March and April 2014 reveals a systematic cold bias in mean temperatures across all altitudes and latitudes, particularly in the mid-latitudes where the bias is about 3–5 K, unless mean temperature nudging is applied. In the upper-troposphere/lower stratosphere, the humidity of the nudged GCM simulations shows a wet bias, while a dry bias is observed at lower altitudes. These biases result in overestimated regions for contrail formation in GCM simulations compared to reanalysis data. A point-by-point comparison along flown trajectories with measurement aircraft data shows similar biases. Exploring relative humidity over ice (RHice) threshold values for identifying ice-supersaturation regions provides insights into the risks of false alarms for contrail formation, together with information on hit rates. Accepting a false alarm rate of 16 % results in a hit rate of about 40 % (RHice threshold 99 %), while aiming for an 80 % hit rate increases the false alarm rate to at least 35 % (RHice threshold 91–94 %). A comprehensive one-day case study, involving aircraft-based observations and satellite data, confirms contrail detection in regions identified as potential contrail coverage areas by the GCM.

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Short summary
Our study examines how temperature and humidity representations influence contrail (-cirrus)...