the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 09 Feb 2023
Lagrangian transport simulations using the extreme convection parametrization: an assessment for the ECMWF reanalyses
Paul Konopka
Jan Clemens
Bärbel Vogel
Abstract. Atmospheric convection plays a key role in tracer transport from the planetary boundary layer to the free troposphere. Lagrangian transport simulations driven by global meteorological input data such as the European Centre for Medium-Range Weather Forecasts (ECMWF's) ERA5 and ERA-Interim reanalysis typically lack proper explicit representations of convective up- and downdrafts because of the limited spatiotemporal resolution of the input data. Lagrangian transport simulations for the troposphere can be improved by applying parametrizations to better represent the effects of unresolved convective transport in the global meteorological reanalysis data. Here, we implemented and assessed the effects of the extreme convection parametrization (ECP) in the Massive Parallel Trajectory Calculations (MPTRAC) model. The ECP is conceptually simple. It requires the convective available potential energy (CAPE) and the height of the equilibrium level (EL) of the meteorological data for input. Assuming that unresolved convective events yield well-mixed vertical columns of air, the ECP randomly redistributes the air parcels vertically between the surface and the EL, if CAPE is present. We analyzed statistics of explicitly resolved and parametrized convective updrafts and found that the frequencies of strong updrafts due to the ECP, i.e., 20 K potential temperature increase over 6 h or more, increase by 2 to 3 orders of magnitude for ERA5 and 3 to 5 orders of magnitude for ERA-Interim compared to the explicitly resolved updrafts. To assess the effects of the ECP on tropospheric tracer transport, we conducted transport simulations for the artificial tracer e90, which is released globally near the surface and has a constant e-folding lifetime of 90 days throughout the atmosphere. The e90 simulations were conducted for the year 2017 with both, ERA5 and ERA-Interim data. Next to sensitivity tests on the choice of the CAPE threshold, an important tuning parameter of the ECP, we suggest a possible improvement of the ECP method, i.e., to take into account the convective inhibition (CIN) indicating the presence of warm, stable layers that prevent convective updrafts in the real atmosphere. While ERA5 has higher spatiotemporal resolution and explicitly resolves more convective updrafts than ERA-Interim, we found there is still a need for both reanalyses to apply a convection parametrization such as the ECP to better represent tracer transport from the planetary boundary layer into the free troposphere on the global scale.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
(10693 KB)
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(10693 KB) - BibTeX
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- Final revised paper
Journal article(s) based on this preprint
Lars Hoffmann et al.
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2023-72', Anonymous Referee #1, 22 Mar 2023
This is a well written paper describing the implementation of the extreme convection parameterization into the MPTRAC model and sensitivity simulations describing the impact of using this parameterization on tracer transport. My recommendation is for this paper to be published with minor edits.
It is mentioned in Section 2.2 that MPTRAC is used to investigate free troposphere and stratosphere transport processes. It does not mention why it is not used for boundary layer applications until the end of Section 3.7. This should be mentioned in Section 2.2 followed by a discussion of the importance of the depth the tracers are initialized near the surface so they cover the depth of the PBL. I recommend moving Section 3.7 into or soon after Section 2.2.
Throughout the paper, meteorological model output and reanalysis products are referred to as data. I prefer the word 'data' be reserved for measurements. I suggest re-wording this throughout the paper. For example, I suggest changing the second sentence of the abstract to something like: “Lagrangian transport simulations driven by meteorological fields from global models or reanalysis products, such as the European Centre for Medium-Range Weather Forecasts’ (ECMWF’s) ERA5 and ERA-Interim reanalysis, typically lack proper explicit representations of convective up- and downdrafts because of the limited spatiotemporal resolution of the meteorology.
Introduction, page 2, line 27: add comma between conditions and such: “…severe weather conditions, such as …”
Throughout the paper it is mentioned that trajectories were performed. I suggest rephrasing that 10^6 trajectories were performed to a dispersion simulation with 10^6 particles. I think of a trajectory as following the mean wind whereas a dispersion simulation includes a turbulent component.
Throughout the Results section (especially toward the beginning), be abundantly clear that ECP simulations is a simulation with a CAPE threshold of 0. Same for all of the figure captions.
Section 3.2, page 11, line 249 – page 12, line 250: Is this shown that it is similar to Konopka et al. (2022)?
Section 3.6: Suggest changing the title of this section: Change “Improvement” to “Sensitivity”
Citation: https://doi.org/10.5194/egusphere-2023-72-RC1 - RC2: 'Comment on egusphere-2023-72', Anonymous Referee #2, 31 Mar 2023
- AC1: 'Comment on egusphere-2023-72', Lars Hoffmann, 12 May 2023
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-72', Anonymous Referee #1, 22 Mar 2023
This is a well written paper describing the implementation of the extreme convection parameterization into the MPTRAC model and sensitivity simulations describing the impact of using this parameterization on tracer transport. My recommendation is for this paper to be published with minor edits.
It is mentioned in Section 2.2 that MPTRAC is used to investigate free troposphere and stratosphere transport processes. It does not mention why it is not used for boundary layer applications until the end of Section 3.7. This should be mentioned in Section 2.2 followed by a discussion of the importance of the depth the tracers are initialized near the surface so they cover the depth of the PBL. I recommend moving Section 3.7 into or soon after Section 2.2.
Throughout the paper, meteorological model output and reanalysis products are referred to as data. I prefer the word 'data' be reserved for measurements. I suggest re-wording this throughout the paper. For example, I suggest changing the second sentence of the abstract to something like: “Lagrangian transport simulations driven by meteorological fields from global models or reanalysis products, such as the European Centre for Medium-Range Weather Forecasts’ (ECMWF’s) ERA5 and ERA-Interim reanalysis, typically lack proper explicit representations of convective up- and downdrafts because of the limited spatiotemporal resolution of the meteorology.
Introduction, page 2, line 27: add comma between conditions and such: “…severe weather conditions, such as …”
Throughout the paper it is mentioned that trajectories were performed. I suggest rephrasing that 10^6 trajectories were performed to a dispersion simulation with 10^6 particles. I think of a trajectory as following the mean wind whereas a dispersion simulation includes a turbulent component.
Throughout the Results section (especially toward the beginning), be abundantly clear that ECP simulations is a simulation with a CAPE threshold of 0. Same for all of the figure captions.
Section 3.2, page 11, line 249 – page 12, line 250: Is this shown that it is similar to Konopka et al. (2022)?
Section 3.6: Suggest changing the title of this section: Change “Improvement” to “Sensitivity”
Citation: https://doi.org/10.5194/egusphere-2023-72-RC1 - RC2: 'Comment on egusphere-2023-72', Anonymous Referee #2, 31 Mar 2023
- AC1: 'Comment on egusphere-2023-72', Lars Hoffmann, 12 May 2023
Peer review completion
Journal article(s) based on this preprint
Lars Hoffmann et al.
Lars Hoffmann et al.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
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