The Yellow-Green Rain: Pollen

Well, it's really springtime in Mississippi now. I almost want to have an umbrella when I'm in the yard to keep the pollen from falling down on me. Of course, that wouldn't keep it out of my nose. Luckily it's not bothering me nearly so bad as it's bothering my children. After running around outside, they come inside looking for Kleenex to wipe their sniffly noses. Over the weekend their allergies were bad enough at night to significantly cut into my sleep.

One factor in the pollen problem is the fact that we haven't had significant rain in several days. Air quality and pollen levels normally improve after rain, due to the "scavenging" effect of the raindrops in removing aerosols from the atmosphere. Of course, the moist conditions can also help to trigger the release of more pollen. A big obstacle to better coordination in research, understanding, and forecasting of health impacts from weather is that we have very little idea what is floating around out there on any given day, especially for global transport. It is fairly well established that a significant proportion of aerosols are biogenic, such as pollen. But it is still quite difficult to routinely collect and identify them.

And we really don't know how large of an impact biogenic aerosols may have on the weather and climate. Potential direct impacts could include nucleation of cloud droplets and radiative interactions. Some of the issues involved were discussed in a 2005 article in the Bulletin of the American Meteorological Society. The role of aerosols is also summarized in this NASA brochure. Or you can check out the slightly sensationalized article "Airborne Dandruff Can Turn On Rain" from Australia.