Preprints
https://doi.org/10.5194/egusphere-2022-978
https://doi.org/10.5194/egusphere-2022-978
03 Jan 2023
 | 03 Jan 2023

Effect of radiation interaction and aerosol processes on ventilation and aerosol concentrations in a real urban neighbourhood in Helsinki

Jani Strömberg, Xiaoyu Li, Mona Kurppa, Heino Kuuluvainen, Liisa Pirjola, and Leena Järvi

Abstract. Large eddy simulation (LES) provides an optimal tool to examine air pollutant concentrations at high temporal and spatial resolutions within urban neighborhoods. The local mixing conditions are to a large extent a result of building morphology and thermal conditions impacting mechanically and thermally driven turbulence. However, the impact of thermal conditions on local air pollutant concentrations in real urban environments is not well understood nor the importance of including thermal processes in LES. Furthermore, LES of aerosol particle concentrations in urban areas rarely include aerosol processes, but rather aerosols are treated as passive scalars. The aim of this study is to examine the importance of radiative heating and aerosol processes in simulating local aerosol particle concentrations in a wide street canyon and its surroundings in Helsinki under morning rush hour with calm wind conditions using the LES model PALM. The model outputs are evaluated against mobile laboratory measurements of air temperature and total particle number concentration (Ntot), and drone measurements of lung deposited surface area (LDSA).

The inclusion of radiation interaction in LES has a significant impact on simulated near surface temperatures in our study domain increasing them on average by 3.8 °C from 8.6 °C to 12.4 °C. The thermal processes further strengthen the flow field, and enhance the ventilation of air pollutants from the street canyon by altering the canyon vortex. The enhanced ventilation reduces the pedestrian level (4 m) Ntot by 53 %. The reduction of Ntot due to aerosol processes is smaller, only 18 %. Aerosol processes have a larger effect in the smallest particle range, decreasing particle concentrations below 10 nm by up to 2.5 orders of magnitude whereas radiation interaction is more important in the larger particle range. Aerosol processes have a stronger impact than ventilation on LDSA, whereas radiation interaction shows a larger decrease in PM2.5 than in other aerosol metrics. The inclusion of radiation interaction in PALM improves the modelled near-surface temperatures and Ntot when compared to mobile laboratory measurements reducing the bias between the modelled and measured temperatures from -3.9 °C to +0.2 °C, and concentrations from +98 % to -13 %. With both aerosol and radiation interaction on, the underestimation was 16 %, which might be due to overestimation of the ventilation. The results show how inclusion of radiative interaction, and to a lesser extent aerosol processes, on LES are important for realistic simulation of near surface aerosol particle concentrations. This particularly in a calm wind situation such as modelled in this study.

Journal article(s) based on this preprint

24 Aug 2023
Effect of radiation interaction and aerosol processes on ventilation and aerosol concentrations in a real urban neighbourhood in Helsinki
Jani Strömberg, Xiaoyu Li, Mona Kurppa, Heino Kuuluvainen, Liisa Pirjola, and Leena Järvi
Atmos. Chem. Phys., 23, 9347–9364, https://doi.org/10.5194/acp-23-9347-2023,https://doi.org/10.5194/acp-23-9347-2023, 2023
Short summary

Jani Strömberg et al.

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-978', Anonymous Referee #1, 25 Jan 2023
  • RC2: 'Comment on egusphere-2022-978', Anonymous Referee #3, 27 Mar 2023
  • AC1: 'Comment on egusphere-2022-978', Jani Strömberg, 07 May 2023

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-978', Anonymous Referee #1, 25 Jan 2023
  • RC2: 'Comment on egusphere-2022-978', Anonymous Referee #3, 27 Mar 2023
  • AC1: 'Comment on egusphere-2022-978', Jani Strömberg, 07 May 2023

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Jani Strömberg on behalf of the Authors (29 May 2023)  Author's response   Author's tracked changes   Manuscript 
ED: Referee Nomination & Report Request started (08 Jun 2023) by Yun Qian
RR by Anonymous Referee #3 (17 Jun 2023)
RR by Anonymous Referee #1 (24 Jun 2023)
ED: Publish as is (25 Jun 2023) by Yun Qian
AR by Jani Strömberg on behalf of the Authors (04 Jul 2023)  Manuscript 

Journal article(s) based on this preprint

24 Aug 2023
Effect of radiation interaction and aerosol processes on ventilation and aerosol concentrations in a real urban neighbourhood in Helsinki
Jani Strömberg, Xiaoyu Li, Mona Kurppa, Heino Kuuluvainen, Liisa Pirjola, and Leena Järvi
Atmos. Chem. Phys., 23, 9347–9364, https://doi.org/10.5194/acp-23-9347-2023,https://doi.org/10.5194/acp-23-9347-2023, 2023
Short summary

Jani Strömberg et al.

Data sets

Input files and scripts for creating PALM simulation input files on Mäkelänkatu in Helsinki, Finland | Datasets and scripts to create input files for running PALM simulations Mona Kurppa, Jani Strömberg https://doi.org/10.5281/zenodo.3839684

Mäkelänkatu Simulations 2022 | Datasets to run PALM around Mäkelänkatu, Helsinki to study aerosol processes and radiation interaction Mona Kurppa, Jani Strömberg https://doi.org/10.5281/zenodo.7115705

Mäkelänkatu Scripts 2022 | Scripts used to analyze the output data from https://zenodo.org/record/7115705 Jani Strömberg, Mona Kurppa https://doi.org/10.5281/zenodo.7124021

Jani Strömberg 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.

Short summary
In this study we concluded that with low wind speeds, solar radiation has a larger decreasing effect (53 %) on pollutant concentrations than aerosol processes (18 %). Additionally, our results showed that with solar radiation included, pollutant concentrations were closer to observations (-13 %) than with only aerosol processes (+97 %). This has implications when planning simulations under calm conditions such as our case and deciding whether or not simulations need to include these processes.