In Trees Make Rain V we saw how trees enable microbes to put just the right kind of particles in the air to make it rain. It turns out that these are the most productive of all three known types of nucleating particles:
- Meteor dust particles, which serve as ice nucleators mostly at temperatures colder than -15 degrees Celsius);
- Inorganic soil particles (mainly clays), which also serve as ice nucleators mostly at temperatures colder than -15 degrees Celsius; and
- Biological particles, which serve as ice nucleators temperatures as warm as, or warmer than, -5 degrees Celsius.
This is shown in detail in a paper called “The Biologic Origin of Snowflakes and Raindrops” by the Suburban Emergency Management Project.
The most active ice nucleators are biological in origin, declare Christner, et al. in their paper recently published in Science (February 29, 2008). (11) “This is important because the formation of ice in clouds is required for snow and most rainfall. Dust and soot particles can serve as ice nuclei, but biological ice nuclei are capable of catalyzing freezing at much warmer temperatures”, the researchers explain. (14) In other words, a mechanism exists whereby snowflakes and other precipitation can form when cloud temperatures in the troposphere are relatively warm.
Here’s the link, http://www.nonaiswa.org/wordpress/orgin-of-the-snowflakes/
and archived as a pdf: The_Biologic_Origin_of_Snowflakes_and_Raindrops
and here’s the referenced article (11): Ubiquity of Biological Ice Nucleators in Snowfall
See also Evidence for biological shaping of hair ice (pdf, archived here: bg-12-4261-2015)
and a related article: From rain clouds to ‘hair ice’: how microscopic organisms engineer Earth’s climate
archived here: microscopic_organisms_engineer_climate.pdf