EGU21-10402
https://doi.org/10.5194/egusphere-egu21-10402
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

The Relationship Between Atmospheric Boundary Layer Structure, Brown Haze, and Air Pollution in Auckland, New Zealand

Hannah Marley1, Kim Dirks2, Andrew Neverman3, Ian McKendry4, and Jennifer Salmond5
Hannah Marley et al.
  • 1School of Environment, Faculty of Science, The University of Auckland, Auckland, New Zealand (hmar717@aucklanduni.ac.nz)
  • 2Department of Civil and Environmental Engineering, Faculty of Engineering, The University of Auckland, Auckland, New Zealand
  • 3Manaaki Whenua – Landcare Research, Palmerston North, New Zealand
  • 4Department of Geography, Faculty of Arts, University of British Columbia, Vancouver, Canada
  • 5School of Environment, Faculty of Science, The University of Auckland, Auckland, New Zealand

A brown air pollution haze that forms over some international cities during the winter has been found to be associated with negative health outcomes and high surface air pollution levels. Previous research has demonstrated a well-established link between the structure of the atmospheric boundary layer (ABL) and surface air quality; however, the degree to which the structure of the ABL influences for formation of local-scale brown haze is unknown. Using continuous ceilometer data covering seven consecutive winters, we investigate the influence of the structure of the ABL in relation to surface air pollution and brown haze formation over an urban area of complex coastal terrain in the Southern Hemisphere city of Auckland, New Zealand. Our results suggest the depth and evolution of the ABL has a strong influence on severe brown haze formation. When days with severe brown haze are compared with those when brown haze is expected but not observed (based on favorable meteorology and high surface air pollution levels), days with severe brown haze are found to coincide with significantly shallower daytime convective boundary layers (~ 48% lower), and the nights preceding brown haze formation are found to have significantly shallower nocturnal boundary layers (~ 28% lower). On severe brown haze days the growth rate during the morning transition phase from a nocturnal boundary layer to a convective daytime boundary layer is found to be significantly reduced (70 m h-1) compared to days on which brown haze is expected but not observed (170 m h-1). Compared with moderate brown haze, severe brown haze conditions are found to be associated with a significantly higher proportion of days with a distinct residual layer present in the ceilometer profiles, suggesting the entrainment of residual layer pollutants may contribute to the severity of the haze. This study illustrates the complex interaction between the ABL structure, air pollution, and the presence of brown haze, and demonstrates the utility of a ceilometer instrument in understanding and predicting the occurrence of brown haze events.

How to cite: Marley, H., Dirks, K., Neverman, A., McKendry, I., and Salmond, J.: The Relationship Between Atmospheric Boundary Layer Structure, Brown Haze, and Air Pollution in Auckland, New Zealand, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10402, https://doi.org/10.5194/egusphere-egu21-10402, 2021.

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