Preprints
https://doi.org/10.5194/acp-2021-288
https://doi.org/10.5194/acp-2021-288

  12 May 2021

12 May 2021

Review status: this preprint is currently under review for the journal ACP.

Extreme Ice Crystal Events Linked to Biomass and Fossil Fuel Combustion

Graciela B. Raga1, Darrel Baumgardner2, Blanca Rios1, Yanet Díaz-Esteban1, Alejandro Jaramillo1, Martin Gallagher3, Bastien Sauvage5, Pawel Wolff5, and Gary Lloyd3,4 Graciela B. Raga et al.
  • 1Centro de Ciencias de la Atmósfera, Universidad Nacional Autónoma de México, Mexico City, Mexico
  • 2Droplet Measurement Technologies, LLC, Longmont, CO, USA
  • 3Centre for Atmospheric Science, University of Manchester, Manchester M13 9PL, UK
  • 4National Centre for Atmospheric Science (NCAS), University of Manchester, Manchester M13 9PL, UK
  • 5Laboratoire d'aérologie (LA), CNRS UMR-5560 et Observatoire Midi-Pyrénées, Université de Toulouse, France

Abstract. Eight years of upper tropospheric (UT) ice crystal measurements with the Backscatter Cloud Probe (BCP), operated as part of the In-Service Aircraft for a Global Observing System (IAGOS), have been analyzed to assess the frequency and characteristics of extreme ice crystal events (EIE), defined in this study as encounters with clouds that have number concentrations exceeding 5000 L−1. A total of 6490 events, in clouds of horizontal extent ≥ 2.5 km, were identified during the period from December 2011 to March 2020 in the global band between 30° S and 30° N. Evaluation of in situ measurements of carbon monoxide in these UT clouds, combined with back-trajectories and carbon monoxide emission inventories, allow the identification of regional anthropogenic sources. An evaluation of low- and upper-level kinematic variables from the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2), combined with spatial distribution of aerosol optical depth and regions of biomass burning, reveal the physical mechanism by which the particles are lofted to flight levels in regions of deep convection. The maps of lightning frequency derived from the World Wide Lightning Location Network (WWLLN) contribute additional evidence of the role of deep convection lofting ice forming aerosols to the UT. The MERRA-2 analysis shows clear spatial correlations that link dust, black carbon (BC), organic carbon (OC) and sulfate particles with regions of EIE. Given the composition of the source aerosols and the nature of their transport to the UT, the ice clouds are likely of liquid origin whereby droplets formed on these particles are lofted and freeze heterogeneously as have been reported in previous studies. The results from this study have important ramifications related to climate change, satellite measurement validation, weather forecasting and aircraft operations.

Graciela B. Raga et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-288', Anonymous Referee #2, 10 Jun 2021
  • RC2: 'Comment on acp-2021-288', Anonymous Referee #3, 24 Jun 2021
  • RC3: 'Comment on acp-2021-288', Anonymous Referee #1, 06 Jul 2021

Graciela B. Raga et al.

Graciela B. Raga et al.

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Short summary
The In-Service Aircraft for a Global Observing System (IAGOS) is a small fleet of commercial aircraft that carry a suite of meteorological, gas, aerosol and cloud sensors and have been measuring worldwide for almost 9 years, since late 2011. Extreme Ice Events (EIE) have ben identified from the IAGOS cloud measurements and linked to surface emissions for biomass and fossil fuel consumption. The results reported here are highly relevant for climate change and flight operations forecasting.
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