Pollen grains emitted from vegetation can rupture, releasing subpollen particles (SPPs) as fine atmospheric particulates. Previous laboratory research demonstrates potential for SPPs as efficient cloud condensation nuclei (CCN). We develop the first model of atmospheric pollen grain rupture, and implement the mechanism in regional climate model simulations over spring pollen season in the United States with a CCN-dependent moisture scheme. The source of SPPs (surface or in-atmosphere) depends on region and sometimes season, due to the distribution of relative humidity and rain. Simulated concentrations of SPPs are approximately 1-10 or 1-1,000 cm-3, depending on the number of SPPs produced per pollen grain (nspg). Lower nspg (103) produces a negligible effect on precipitation, but high nspg (106) in clean continental CCN background concentrations (100 CCN cm-3) shows SPPs suppress average seasonal precipitation by 32% and shift rates from heavy to light while increasing dry days. This effect is likely smaller for polluted air.
pollen_rupture_precipitation_BASE_ensemble_daily.nc - data for BASE ensemble average
pollen_rupture_precipitation_SPPHIGH_ensemble_daily.nc - data for SPPHIGH ensemble average
pollen_rupture_precipitation_SPPLIT_ensemble_daily.nc - data for SPPLIT ensemble average
Citation to related publication:
Wozniak, M. C., Solmon, F., Steiner, A. L. (2018). Pollen Rupture and Its Impact on Precipitation in Clean Continental Conditions. Geophysical Research Letters, 45(14), 7156-7164. https://doi.org/10.1029/2018GL077692