Preprints
https://doi.org/10.5194/egusphere-2023-1026
https://doi.org/10.5194/egusphere-2023-1026
20 Jun 2023
 | 20 Jun 2023

Evaluation of vertical transport in the Asian monsoon 2017 from CO2 reconstruction in the ERA5 and ERA-Interim reanalysis

Bärbel Vogel, Michael Volk, Johannes Wintel, Valentin Lauther, Jan Clemens, Jens-Uwe Grooß, Gebhard Günther, Lars Hoffmann, Johannes C. Laube, Rolf Müller, Felix Ploeger, and Fred Stroh

Abstract. Atmospheric concentrations of many greenhouse gases especially CO2 are increasing globally. In particular the rapid increase of anthropogenic CO2 emissions in Asia contributes strongly to the acceleration of the CO2 growth rate in the atmosphere. During the Asian monsoon season, greenhouse gases as well as pollution emitted near the ground rapidly propagate up to an altitude of 13 km (~360 K potential temperature) with slower ascent and mixing with the stratospheric background above. However, CO2 sources in South Asia are poorly quantified. Here, differences in transport of air in the regions of the Asian summer monsoon 2017 were inferred using the Chemical Lagrangian Model of the Stratosphere (CLaMS) driven by three data sets, namely two ECMWF reanalyses in different resolutions (ERA-Interim, ERA5 and ERA5 1° x 1°). These model results are assessed using unique airborne measurements up to altitudes of ~20 km (~475 K) during the Asian summer monsoon 2017 conducted with the Geophysica aircraft during the StratoClim campaign in Nepal. Trajectory-based transport times, air mass source regions at the Earth's surface, mean effective ascent rates and age spectra as well as mean age of air from 3-dimensional CLaMS simulations are compared using the three data sets and evaluated by observation-based ascent rates. Our findings confirm that because of a better spatial and temporal resolution, ERA5 reanalysis yields a better representation of convection than ERA-Interim. Further, our findings show that transport times from the surface to the Asian monsoon anticyclone as well as the origin of air at the Earth's surface are both very sensitive to the used reanalysis. Above 430 K, the mean effective ascent rates derived from ERA5 back-trajectories and ERA5 1° x 1° (~0.2–0.3 K/day) are in good agreement with the observation-based mean ascent rates inferred from long-lived trace gases such as C2F6 and HFC-125 derived from air samples collected by the whole air sampler aboard Geophysica. Mean effective ascent rates derived from ERA-Interim back-trajectories are much faster ~0.5 K/day at these altitudes. In the Asian monsoon region at 470 K, mean age of air is larger than 3 years for ERA5 1° x 1° and about 2 years for ERA-Interim, whereas an observation-based age of air is up to 2.5 years.

A reliable reconstruction (simulation) of vertical CO2 profiles during the Asian monsoon is a challenge for model simulations because the seasonal variability of CO2 at the ground, mixing with aged stratospheric air and the vertical velocities (including convection as well as vertical ascent caused by diabatic heating in the UTLS) have to be represented accurately in the simulations. Up to 410 K, the presented CO2 reconstruction agrees best with high-resolution in situ aircraft CO2 measurements using ERA5 compared to ERA5 1° x 1° and ERA-Interim, indicating a better representation of Asian monsoon transport for the newer ECMWF reanalysis product ERA5. Above 410 K the uncertainties of the CO2 reconstruction are increasing because of mixing with aged air.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.

Journal article(s) based on this preprint

11 Jan 2024
Evaluation of vertical transport in ERA5 and ERA-Interim reanalysis using high-altitude aircraft measurements in the Asian summer monsoon 2017
Bärbel Vogel, C. Michael Volk, Johannes Wintel, Valentin Lauther, Jan Clemens, Jens-Uwe Grooß, Gebhard Günther, Lars Hoffmann, Johannes C. Laube, Rolf Müller, Felix Ploeger, and Fred Stroh
Atmos. Chem. Phys., 24, 317–343, https://doi.org/10.5194/acp-24-317-2024,https://doi.org/10.5194/acp-24-317-2024, 2024
Short summary
Bärbel Vogel, Michael Volk, Johannes Wintel, Valentin Lauther, Jan Clemens, Jens-Uwe Grooß, Gebhard Günther, Lars Hoffmann, Johannes C. Laube, Rolf Müller, Felix Ploeger, and Fred Stroh

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1026', Anonymous Referee #1, 04 Sep 2023
  • RC2: 'Comment on egusphere-2023-1026', Anonymous Referee #2, 21 Sep 2023

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1026', Anonymous Referee #1, 04 Sep 2023
  • RC2: 'Comment on egusphere-2023-1026', Anonymous Referee #2, 21 Sep 2023

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Bärbel Vogel on behalf of the Authors (03 Nov 2023)  Author's response   Author's tracked changes   Manuscript 
ED: Referee Nomination & Report Request started (06 Nov 2023) by Bernd Funke
RR by Anonymous Referee #2 (18 Nov 2023)
ED: Publish as is (20 Nov 2023) by Bernd Funke
AR by Bärbel Vogel on behalf of the Authors (22 Nov 2023)  Manuscript 

Journal article(s) based on this preprint

11 Jan 2024
Evaluation of vertical transport in ERA5 and ERA-Interim reanalysis using high-altitude aircraft measurements in the Asian summer monsoon 2017
Bärbel Vogel, C. Michael Volk, Johannes Wintel, Valentin Lauther, Jan Clemens, Jens-Uwe Grooß, Gebhard Günther, Lars Hoffmann, Johannes C. Laube, Rolf Müller, Felix Ploeger, and Fred Stroh
Atmos. Chem. Phys., 24, 317–343, https://doi.org/10.5194/acp-24-317-2024,https://doi.org/10.5194/acp-24-317-2024, 2024
Short summary
Bärbel Vogel, Michael Volk, Johannes Wintel, Valentin Lauther, Jan Clemens, Jens-Uwe Grooß, Gebhard Günther, Lars Hoffmann, Johannes C. Laube, Rolf Müller, Felix Ploeger, and Fred Stroh
Bärbel Vogel, Michael Volk, Johannes Wintel, Valentin Lauther, Jan Clemens, Jens-Uwe Grooß, Gebhard Günther, Lars Hoffmann, Johannes C. Laube, Rolf Müller, Felix Ploeger, and Fred Stroh

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Short summary
Atmospheric concentrations of the greenhouse gas carbon dioxide have increased substantially because of human activities. However, their sources in South Asia are poorly quantified. Here, we present high temporal and vertical resolution aircraft measurements up to 20 km during the Asian summer monsoon where rapid upward transport of surface pollutants to greater altitudes occurs. Using model simulations, we successfully reconstruct observed CO2 profiles and evaluate meteorological reanalysis.