Rachel Hawker

Rachel Hawker




Research interests

My current research involves using the Met Office Unified Model (UM) and the Cloud Aerosol Interacting Microphysics Module (CASIM) to conduct high resolution simulations of deep convective clouds in the Tropical Atlantic. These simulations are used to determine the separate and interacting impacts of heterogeneous freezing and secondary ice nucleation (specifically the Hallett Mossop process). The Tropical Atlantic is an important climatological region and is subject to a large dust loading from the adjacent Saharan desert. Dust is an effective ice nucleating particle (INP) and can impact cloud properties and lifetime. There is a large amount of literature documenting the ice nucleating ability of dust as measured in laboratory and field-based studies. However, there is still uncertainty regarding the best way to represent dust in models and there is a large number of parameterisations to choose from. The impact on cloud properties of choosing one method of ice nucleation over another is not conclusively quantified, something we aim to address in my work. INP alone cannot account for the large ice number concentrations observed in convective clouds indicating the importance of a secondary ice production mechanism. The most well-known mechanism is the Hallett Mossop process. However, the rate of ice production by this mechanism is not certain along with the location or time at which Hallett Mossop will occur in a cloud's lifetime. In my work I look at the effect on cloud properties of Hallett Mossop occuring within a cloud.



Price, H.C., Baustian, K.J., McQuaid, J.B., Blyth, A., Bower, K.N., Choularton, T., Cotton, R.J., Cui, Z., Field, P.R., Gallagher, M., Hawker, R., Merrington, A., Miltenberger, A., Neely, R.R., Parker, S.T., Rosenberg, P.D., Taylor, J.W., Trembath, J., Vergara-Temprado, J., Whale., T.F., Wilson, T.W., Young, G. and Murray, B.J., 2018. Atmospheric Ice?Nucleating Particles in the Dusty Tropical Atlantic. Journal of Geophysical Research: Atmospheres, 123(4), pp.2175-2193.


  • BSc Environmental Science, University of East Anglia

Research groups and institutes

  • Atmospheric Chemistry and Aerosols
  • Institute for Climate and Atmospheric Science