Multiphase mass transfer in convective systems with a particular reference to natural and urban aerosols

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• Siddharth Gumber (British Antarctic Survey and St. Edmund's College, University of Cambridge)
• Friday 22 March 2024, 14:00-15:00
• BAS Cambridge Seminar Room 2 and Zoom.

If you have a question about this talk, please contact Siddharth Gumber.

South Asia constitutes about 24% of the world’s population and grapples with the menace of anthropogenically sourced soot and black carbon particles. This talk will discuss how particles sourced from unregulated vehicular traffic over congested cities impact the lower boundary layer resulting in reduced visibility and other micro-climatic perturbations. Whilst the genesis and consequences of semi-direct radiative effects are well documented, the subsequent transformative stages of ageing of such particles in an atmosphere rich in inorganic pollutant gases are not fully investigated. In this seminar, I shall talk about first quantifying the particle size distribution of emissions from diesel vehicles and then discuss the chemico-thermodynamical effects that operate upon such emissions where the assumption of hydrophilicity breaks down. Binary diffusivity profiles are fine-tuned by accounting for the finite dipole moment of water vapour with a sophisticated Lennard-Jones diffusivity model. This was necessary because laboratory estimates only pertain to sea level pressures and temperatures, whilst the scavenging action on particle surfaces operates much higher up at lower pressures and temperatures because strong eddies buoy particle mixtures up through dynamical processes. This talk will crucially highlight that moist thermodynamics is mediated by alterations in material accretion on sub-micron vehicle-generated particles. These particles behave as condensation nuclei for subsequent growth involving the microphysical processes of auto-conversion, accretion, collision and coalescence within the remit of Computational Fluid Dynamical (CFD) models. Microphysics impacts the adiabaticity of isolated parcels of turbulent eddies, which is explored through parcel and large-scale dynamical models with resolved boundary layer eddies and multiphase cloud patches. As an important outcome, the results from this work might provide crucial information to city planners and regulators dealing with the relocation of inhabitants of low-lying shantytowns prone to flooding through early-warning systems. Finally, this research has led to conceptual advances on the re-distribution and transformation of vehicle-mediated particles released in complex mixtures of aerosols entailing solution non-ideal effects.

This talk is part of the BAS Atmosphere, Ice and Climate Seminars series.

This talk is included in these lists:

• BAS Atmosphere, Ice and Climate Seminars
• BAS Cambridge Seminar Room 2 and Zoom

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