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SUMMARY:Multiphase mass transfer in convective systems with a particular r
 eference to natural and urban aerosols - Siddharth Gumber (British Antarct
 ic Survey and St. Edmund's College\, University of Cambridge)
DTSTART:20240322T140000Z
DTEND:20240322T150000Z
UID:TALK218689@talks.cam.ac.uk
CONTACT:Siddharth Gumber
DESCRIPTION:South Asia constitutes about 24% of the world's population and
  grapples with the menace of anthropogenically sourced soot and black carb
 on particles. This talk will discuss how particles sourced from unregulate
 d vehicular traffic over congested cities impact the lower boundary layer 
 resulting in reduced visibility and other micro-climatic perturbations. Wh
 ilst the genesis and consequences of semi-direct radiative effects are wel
 l documented\, the subsequent transformative stages of ageing of such part
 icles in an atmosphere rich in inorganic pollutant gases are not fully inv
 estigated. In this seminar\, I shall talk about first quantifying the part
 icle 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 tempe
 ratures\, whilst the scavenging action on particle surfaces operates much 
 higher up at lower pressures and temperatures because strong eddies buoy p
 article 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 beha
 ve as condensation nuclei for subsequent growth involving the microphysica
 l processes of auto-conversion\, accretion\, collision and coalescence wit
 hin the remit of Computational Fluid Dynamical (CFD) models. Microphysics 
 impacts the adiabaticity of isolated parcels of turbulent eddies\, which i
 s explored through parcel and large-scale dynamical models with resolved b
 oundary layer eddies and multiphase cloud patches. As an important outcome
 \, the results from this work might provide crucial information to city pl
 anners and regulators dealing with the relocation of inhabitants of low-ly
 ing shantytowns prone to flooding through early-warning systems. Finally\,
  this research has led to conceptual advances on the re-distribution and t
 ransformation of vehicle-mediated particles released in complex mixtures o
 f aerosols entailing solution non-ideal effects.
LOCATION:BAS Cambridge Seminar Room 2 and Zoom
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