Tinsley, Brian A.

Permanent URI for this collectionhttps://hdl.handle.net/10735.1/6084

Brian A. Tinsley is Professor Emeritus of Physics. He has been actively involved in observational and theoretical research on upper atmosphere processes (Aeronomy) for more than 45 years, and has served on many national and international organizations in this field. An overview of his research consists of two major themes

  • Observational and theoretical work on effects of global atmospheric electricity on weather and climate, both from external (solar wind) and internal (e.g., thunderstorm) sources.
  • Models of effects of current flow in the Global Electric Circuit on charging of aersols and cloud droplets, and effects of such charges on cloud microphysics.

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    Parameterization of Aerosol Scavenging Due to Atmospheric Ionization Under Varying Relative Humidity
    (Amer Geophysical Union, 2017-04-12) Zhang, Liang; Tinsley, Brian A.; 0000 0003 7214 6140 (Tinsley, BA); Zhang, Liang; Tinsley, Brian A.
    Simulations and parameterizations of the modulation of aerosol scavenging by electric charges on particles and droplets for different relative humidities have been made for 3 mu m radii droplets and a wide range of particle radii. For droplets and particles with opposite-sign charges, the attractive Coulomb force increases the collision rate coefficients above values due to other forces. With same-sign charges, the repulsive Coulomb force decreases the rate coefficients, and the short-range attractive image forces become important. The phoretic forces are attractive for relative humidity less than 100% and repulsive for relative humidity greater than 100% and have increasing overall effect for particle radii up to about 1 mu m. There is an analytic solution for rate coefficients if only inverse square forces are present, but due to the presence of image forces, and for larger particles the intercept, weight, and the flow around the particle affecting the droplet trajectory, the simulated results usually depart far from the analytic solution. We give simple empirical parameterization formulas for some cases and more complex parameterizations for more exact fits to the simulated results. The results can be used in cloud models with growing droplets, as in updrafts, as well as with evaporating droplets in downdrafts. There is considered to be little scavenging of uncharged ice-forming nuclei in updrafts, but with charged ice-forming nuclei it is possible for scavenging in updrafts in cold clouds to produce contact ice nucleation. Scavenging in updrafts below the freezing level produces immersion nuclei that promote enhanced freezing as droplets rise above it.

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