Ground-based and satellite observations in the United States indicate that elevated pollen levels during spring contribute to increased cloud ice and precipitation, even in temperatures between -15 and -25 degrees Celsius. Could pollen affect cloud formation?
In this article we are going to tell you How pollen influences cloud formation and precipitation patterns.
Pollen and ice formation
According to Dr. Jan Kretzschmar, lead author of the study, “The laboratory results show that pollen acts as ice nuclei, affecting the freezing temperature of water within clouds and facilitating precipitation.” In the absence of these ice nucleating particles (INPs), cloud water freezes only at temperatures below -38 degrees Celsius. The results of this research were published in Environmental Research Letters.
"In the Breathing Nature Cluster of Excellence project, we asked the question of whether this effect could be observed beyond the confines of the laboratory and examined the impacts of climate change and biodiversity loss on it," says co-author Professor Johannes Quaas, who is a professor of theoretical meteorology in Leipzig and a spokesperson for the Breathing Nature consortium.
The importance of pollen in cloud formation
In a global context, the influence of pollen on ice formation is comparatively minor compared to that of dust, for example. However, its impact is considerable both regionally and seasonally. Especially during spring, substantial amounts of pollen are emitted into the atmosphere, reaching cold air layers.
Kretzschmar explains that due to its size, Pollen has a brief presence in the atmosphere. “Our research highlights the importance of the smallest pollen fragments, which are generated when pollen disintegrates in humid conditions. These tiny particles persist in the air for a long period and, when present in adequate quantities, can penetrate the coldest layers of the atmosphere, thus initiating ice formation.”
Climate change exacerbates the effects of pollen
Human-induced climate change is altering the onset of the pollen season, extending its duration and increasing atmospheric pollen concentrations. These patterns are projected to become more pronounced as the century progresses, possibly leading to an increase in both the frequency and intensity of localized precipitation.
Another facet of the study concerns the importance of biodiversity. Numerous plant species emit substantial amounts of pollen simultaneously each spring, influencing cloud formation and the concentration of ice particles in the atmosphere. Further research into these interactions is essential to improve understanding of the role of pollen in climate evolution and integrate it into future climate models.
Kretzschmar says: “If we accurately simulate the impact of pollen and its interactions with the climate, we can improve the accuracy of our predictions.” The research was carried out in collaboration with the Institute of Meteorology at the University of Leipzig, the Leibniz Institute for Tropospheric Research (TROPOS), the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig and the Max Planck Institute for Biogeochemistry.
Condensation nuclei
Although pollen is commonly associated with plant pollination processes and allergic reactions, it also plays an important role in cloud formation. Pollen grains, along with their constituent particles (known as pollen subparticles or SPPs), They can function as condensation nuclei, serving as a basis for the development of ice clouds or cirrus clouds., which are composed of crystallized water.
A Texas A&M University research team consisting of Brianna Matthews, Alyssa Alsante, and Sarah Brooks examined the influence of humidity variations on the emission of pollen and pollen particles from ryegrass (Lolium sp.) and ragweed (Ambrosia trifida). In addition, the group explored the role of these particles in cloud formation. The results of their study were published in the American Chemical Society's Journal of Earth and Space Chemistry.
Is pollen a contributing factor to climate change?
Ongoing climate change, a consequence of human actions, is causing an increase in global average temperatures, which in turn prolongs the duration of pollen release. When exposed to air humidity, Pollen grains can be broken down into tiny pollen particles less than a micron in size.
Both pollen grains and particles have the ability to accumulate and trigger the nucleation of droplets within the atmosphere. This phenomenon leads to the creation of multiple clouds that maintain or preserve their water reserves. Although this water retention can be advantageous by reflecting solar radiation back into space, thus contributing to the cooling of the Earth, also has the potential to capture and re-emit heat radiating from the Earth's surface.
This phenomenon is part of a beneficial feedback system, known as cloud-greenhouse feedback, which contributes to the intensification of global warming.
Pollen analysis and climate modelling
To understand the impact of humidity and wind on pollen, researchers collected pollen samples from ryegrass and ragweed, exposing them to varying degrees of air humidity and brief bursts of wind inside a fully equipped chamber. This simulation was designed to replicate conditions found in the natural environment.
The research team evaluated the number of SPPs associated with each pollen grain and their nucleation capabilities. Unexpectedly, the estimated SPPs for these plants were significantly lower than previous experiments had indicated; specifically, The measurements were found to be between 10 and 100 times greaterThis discrepancy in experimental results may be attributed to the previous use of less precise techniques to disperse pollen and generate SPP.
The researchers found that whole pollen grains, rather than solid pollen particles, were more efficient at facilitating cloud formation. The parameters reviewed, along with the amounts of emitted particles and pollen grains, have the potential to improve the accuracy of climate models.
I hope that with this information you can learn more about how pollen influences cloud formation and precipitation patterns.