http://discovermagazine.com/2012/apr/07-does-rain-come-from-life-in-the-clouds/?

Summary:  In an April 2012 article in Discover magazine called “Does Rain come from Life in the Skies,” Douglas Fox reports on a growing number of scientists who believe that there are biological ecosystems in the clouds.  These scientists claim that it is these biosystems and how they work that answers the question, why certain clouds form raindrops and other very similar clouds do not.  Scientists already know that pure water can drop in a cloud to -40 degrees F before it freezes and forms ice which is the beginning of rain.  It confused some scientists to find that with dirt or other seeding of the clouds, that rain could form earlier.  The reason it is confusing is that sometimes even though there isn’t enough dust and other debris to form rain and the temperature is not cold enough, it still rains.  Fox flew with atmospheric chemist Kimberly Prather who along with others believe that it is the amount and type of bacteria that gets kicked up with the dust that determines whether raindrops are formed.  When studying clouds they have found bacteria with “ice genes” which make it easy for these bacteria to form ice.  Microbiologists are now finding and listing bacteria that have this particular ability to cause rain and believe that it is an entire ecosystem that creates rain.  Even more amazing is that it is bacteria and dust from Asia and Africa which effect rain in the United States and bacteria from the United States that effect Europe.  Also, the cloud systems are interesting because clouds that may look as though they are not moving or doing anything special are still involved in the constant process of evaporation and condensation.  The maximum amount of time a water droplet can condense before evaporating is 1 hour and clouds last and travel for many hours.  Scientists have discovered that there is a particularly strong bacteria found on rotting leaves called Pseudomonas syringae that can make water freeze at a relatively warm 28 degree F temperature. Obviously there are other scientists which disagree on the importance of bacteria in the clouds and it still remains a question as to whether it is a true biosystem or if it is just another thing that seeds the clouds and makes the weather harder to predict.

Reaction:  The reason I found this article interesting is that it always seems like the weather people struggle to predict the weather correctly. Maybe some how determining the amount and type of microbes in the clouds, meteorologists could better predict weather patterns. Also, it is weird to think that bacteria in the clouds could influence the weather and rain amounts. If it turns out to be true, maybe we can control the weather and how much rain certain areas get.

Questions

1)      Will this information someday help us to figure out ways around droughts since we can now use more than chemicals to seed clouds?

2)      Could this information be helpful to control flooding by decreasing rainfall when an area is already over come with too much water?

3)      If there are microbes in clouds, then how does air pollution effect them?