Bacteria and fungi are ubiquitous in the atmosphere. The diversity and abundance of airborne microbes may be strongly influenced by atmospheric conditions or even influence atmospheric conditions themselves by acting as ice nucleators. However, few comprehensive studies have described the diversity and dynamics of airborne bacteria and fungi based on culture-independent techniques. We document ...

[1] This study investigates the effects of cloud condensation nuclei (CCN) and ice nuclei (IN) on ice formation in mixed-phase clouds using an adiabatic parcel model. The simulations with lower updrafts represent mixed-phase stratiform clouds, and those with higher updrafts represent deep convective clouds. Increasing CCN concentration can lead to more ice crystals with smaller sizes, but does ...

[1] Formation and evolution of cirrostratus in response to weak, uniform, and constant synoptic forcing is simulated using a one-dimensional numerical model with explicit microphysics, in which the particle size distribution in each grid box is fully resolved. A series of tests of the model response to nucleation modes (homogeneous-freezingonly/heterogeneous nucleation) and heterogeneous nuclea...

The aerosol chamber AIDA was used as a moderate expansion cloud chamber with cooling rates at the onset of ice nucleation between –1.3 and –3.0 K min−1 to investigate the nucleation and growth of ice crystals in sulphuric acid, ammonium sulphate, and mineral dust aerosols at temperatures between 196 and 224 K. Supercooled sulphuric acid droplets with mean diameters of about 0.2 to 0.3 μm nuclea...

It is not well understood what determines the degree of supercooling of apoplastic sap in trees, although it determines the number and duration of annual freeze-thaw cycles in a given environment. We studied the linkage between apoplastic ice nucleation temperature, tree water status, and conduit size. We used branches of 10 gymnosperms and 16 angiosperms collected from an arboretum in Helsinki...