Real-time Measurements of Biological Aerosol Particles in Clouds

Some types of biological particles are known to efficiently nucleate ice at relatively warm temperatures in the atmosphere, with the potential to influence cloud microphysical properties and climate. However, the prevalence (or lack thereof) of these particle types in different parts of the atmosphere and in clouds is a matter of debate. Current techniques are mostly limited to near-ground sampling or to limited aircraft sampling with complex instrumentation. Many types of biological particles fluoresce when exposed to ultraviolet light, and the Wideband Integrated Bioaerosol Sensor (WIBS-4A) takes advantage of this characteristic to perform real-time measurements of biological particles. During the IDEAS-2013 test campaign based in Colorado (USA), the WIBS-4A was flown behind a counterflow virtual impactor (CVI) to measure concentrations of biological particles in clouds of different types, temperatures, and altitudes. Preliminary results from this first-ever combination of instruments on the high-performance Gulfstream-V research aircraft will be presented. Concentrations of fluorescent particles measured by the WIBS will also be related to ice nuclei concentrations and properties of particles collected simultaneously on filters.