Cloud Physics

Airborne measurements of cloud and precipitation particles are used to study microphysical processes involved in their formation and evolution.

Clouds form and evolve through the interaction of a range of physical processes. Dynamical processes which may be modulated by radiative heating and cooling lead to the lifting of air parcels and the condensation of water vapour. Microphysical processes lead to the formation of cloud droplets and ice crystals on pre-existing aerosol nuclei and their subsequent growth to form precipitation. We study these processes using a range of instrumentation that is flown on board the FAAM BAe146 research aircraft.

The instrumentation includes a range of probes to both count and size particles spanning the size range 0.1 to several thousand micrometres (0.0001 to several millimetres). These probes use the scattering of laser light from single particles and imaging techniques, both of which can give information on the size and phase (liquid or ice) of the particles. We are also developing improved techniques to measure the bulk ice water content of cold clouds. This can vary by three orders of magnitude between convective clouds in the lower troposphere and cirrus in the upper troposphere.

We work closely with colleagues in the Parametrizations group, from UK universities including Leeds and Manchester and also internationally to provide guidance on the improved representation of cloud and precipitation processes in the Unified Model.

Key Aims

  • Improved understanding of microphysical processes in cloud and precipitation systems.
  • Use of high-resolution numerical models to assist in the interpretation of field observations.
  • Guidance on the development of improved parametrization schemes for microphysical processes in the Unified Model.
  • Development of improved observational techniques to study microphysical processes and bulk cloud properties.

Current projects

  • COPE - the Convective Precipitation Experiment. This field campaign took place in July and August 2013 to examine precipitation from organized convective systems over SW England, using both aircraft, ground-based radar and other supporting observations including additional radiosondes and aerosol measurements. The results will be used to examine the performance of different versions of the Unified Model and their ability quantitatively to forecast precipitation from such systems. The project's UK university participants have a website here.
  • PIKNMIX - this is a flight campaign to examine a variety of mixed-phase cloud systems (those that contain both ice and supercooled liquid water), with the aircraft based at Prestwick in Scotland. One set of measurements was obtained in February 2012 and there will be a further campaign in Nov 2013.
  • COSMICS - Cold-air Outbreak and Sub-Millimetre Ice Cloud Studies. This will continue (from PIKNMIX) the study of cloud processes in cold-air outbreaks, focusing on the transition that takes place between stratiform cloud coverage and open-cellular convection.

Previous projects

  • VOCALS-REx This was a large field project that took place in Oct/Nov 2008. It involved research aircraft and ships in a major study of physical processes in the stratocumulus forming off the coast of Peru and Chile.
  • CONSTRAIN - a UK-based campaign to study microphysical process in ice and mixed-phase cloud layers. The aircraft was based at Prestwick in Scotland for 3 weeks.
  • COALESC - a campaign to study stratocumulus around the UK in Feb/Mar 2011. It also involved ground-based observations by the Meteorological Research Unit.

Last updated: 25 October 2013