Preprints
https://doi.org/10.5194/egusphere-2022-628
https://doi.org/10.5194/egusphere-2022-628
 
20 Jul 2022
20 Jul 2022

Satellite observations of seasonality and long-term trend in cirrus cloud properties over Europe: Investigation of possible aviation impacts

Qiang Li and Silke Groß Qiang Li and Silke Groß
  • Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, D-82234 Oberpfaffenhofen, Germany

Abstract. Aircrafts emit exhaust gases and soot into the atmosphere, which may increase global cirrus cloudiness and as well change the properties of already existing cirrus. In the first COVID-19 lockdown in Europe, changes in cirrus cloud occurrence and properties were detected with the lidar measurements of CALIPSO, which is supposed to be caused by the reduction in civil aviation accordingly. In the last 10 years before COVID, however, aviation grew strongly in terms of CO2 emissions and flight densities in Europe. In the current study, 10-year lidar measurements of cirrus clouds with CALIPSO are analyzed. The Linear contrails and contrail cirrus induced by global aviation have long been known to contribute to climate change by warming the atmosphere. Besides increasing global cirrus cloudiness, aviation may change the properties of the natural cirrus clouds by soot emissions which leads to increased heterogeneous freezing. In the first COVID-19 lockdown in Europe, changes in cirrus cloud properties and occurrence were detected with the lidar measurements of CALIPSO, which is supposed to be caused by the reduction in civil aviation accordingly. In the last 10 years before COVID, however, aviation grew strongly in terms of CO2 emissions and flight densities in Europe. In this study, 10-year lidar measurements of cirrus clouds with CALIPSO are analyzed to determine the seasonality and long-term trends in cirrus clouds as well as their correlations with the ambient temperatures and air traffic. Cirrus clouds follow a distinct seasonal cycle in their occurrence rate (OR) and particle linear depolarization ratio (PLDR) δp. Cirrus clouds appear within a broader altitude range in winter than in summer and they are characterized by larger OR and δp values in winter than in summer. The monthly medians of δp as well as the deseasonalized time series of them in the 10-year period before COVID show both positive trends which are statistically significant according to the Mann-Kendall (MK) significance test. However, the cirrus occurrence shows a negative trend, which might be connected with the background meteorological conditions. Since the cirrus δp strongly depends on the ambient temperatures in cirrus, we further remove the contributions induced by temperatures from the cirrus δp with a simple linear regression model. The derived residuals show significant positive trends with the MK test. To compare the cirrus δp and the air traffic densities, the deseasonalization of the data have previously been conducted since the seasonal cycles in both are not consistent. The deseasonalized time series of the cirrus δp and CO2 emissions from aviation both show an increasing trend and their correlation coefficients are r = 0.54 at the confidence level above 99.5 %. Finally, the comparisons between the cirrus δp and aviation in every season were carried out and revealed a strong correlation in other seasons than in summer.

Qiang Li and Silke Groß

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-628', Anonymous Referee #1, 05 Oct 2022
    • AC1: 'Reply on RC1', Qiang Li, 11 Nov 2022
  • RC2: 'Comment on egusphere-2022-628', Anonymous Referee #2, 14 Oct 2022
    • AC2: 'Reply on RC2', Qiang Li, 11 Nov 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-628', Anonymous Referee #1, 05 Oct 2022
    • AC1: 'Reply on RC1', Qiang Li, 11 Nov 2022
  • RC2: 'Comment on egusphere-2022-628', Anonymous Referee #2, 14 Oct 2022
    • AC2: 'Reply on RC2', Qiang Li, 11 Nov 2022

Qiang Li and Silke Groß

Qiang Li and Silke Groß

Viewed

Total article views: 379 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
267 97 15 379 6 6
  • HTML: 267
  • PDF: 97
  • XML: 15
  • Total: 379
  • BibTeX: 6
  • EndNote: 6
Views and downloads (calculated since 20 Jul 2022)
Cumulative views and downloads (calculated since 20 Jul 2022)

Viewed (geographical distribution)

Total article views: 327 (including HTML, PDF, and XML) Thereof 327 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 29 Nov 2022
Download
Short summary
The IPCC report identified that cirrus clouds have significant impacts on the radiation balance comparable to the CO2 effects, which, however, are still hard to parameterize. The current study aims to investigate the possible aviation impact on cirrus properties based on the analysis of 10-year lidar measurements of CALIPSO. The results reveal that there is a significant positive trend in cirrus depolarization ratio in the last 10 years before COVID, which is strongly correlated with aviation.