3C: UV Radiation and Bio-aerosols

The Tropospheric Ultraviolet-Visible (TUV) model was enhanced to quantify photo-chemical and photo-biological processes in bio-aerosols, including pollen, spores, bacteria, and viruses. These airborne organisms may play a role in ice nucleation, organic chemistry of cloud drops, disease propagation, and evolutionary species distributions.  The DNA of these organism is often exposed and vulnerable to damage by UV radiation. Quantification of the lifetimes of these organisms requires integration of the solar UV spectrum with the biological sensitivity spectra that have been measured in the laboratory for may microbes.  We combined this laboratory knowledge and satellite-observed ozone and clouds in the TUV model, to compute a climatology of the DNA-damaging UV radiation experienced by organisms suspended in air.  Figure 1 shows large geographic and seasonal variations of this radiation at the surface and aloft. These calculations lay the groundwork for future community-wide capability to predict the transport and fate of biological particles, much like current capability of 3D models to represent standard air pollutants, including their atmospheric transformations, transport, and ultimate deposition back to the surface.

DNA-damaging UV fluence at ground-level (lower panels) and at 3 km altitude above ground.
Figure 1: DNA-damaging UV fluence at ground-level (lower panels) and at 3 km altitude above ground. Note different color scales. Climatology derived using satellite-observed ozone and clouds 1979-2000. (Madronich et al., 2017, submitted)