A group of atmospheric chemists have hit upon the first-ever direct detections of biological particles within ice clouds, and have understood the science of climatic change.
The team, led by Kimberly Prather and Kerri Pratt of the University of California at San Diego, Scripps Institution of Oceanography, sampled water droplet and ice crystal residues at high speeds while flying through clouds in the skies over Wyoming, US.
Analysis of the ice crystals revealed that the particles that started their growth were made up almost entirely of either dust or biological material such as bacteria, fungal spores and plant material.
This study is the first to yield direct data on how airborne microorganisms work to influence cloud formation.
"If we understand the sources of the particles that nucleate clouds, and their relative abundance, we can determine their impact on climate," said Pratt, lead author of the research paper.
The effects of tiny airborne particles called aerosols on cloud formation have been some of the most difficult aspects of weather and climate for scientists to understand.
In climate change science, which derives many of its projections from computer simulations of climate phenomena, the interactions between aerosols and clouds represent what scientists consider the greatest uncertainty in modeling predictions for the future.
"By sampling clouds in real time from an aircraft, these investigators were able to get information about ice particles in clouds at an unprecedented level of detail," said Anne-Marie Schmoltner of NSF's (National Science Foundation's) Division of Atmospheric Sciences, which funded the research.
"By determining the chemical composition of the very cores of individual ice particles, they discovered that both mineral dust and, surprisingly, biological particles play a major role in the formation of clouds," she added.
The Ice in Clouds Experiment - Layer Clouds (ICE-L) team mounted a mass spectrometer onto a C-130 aircraft operated by the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, and made a series of flights through a type of cloud known as a wave cloud.
The researchers performed in-situ measurements of cloud ice crystal residues and found that half were mineral dust and about a third were made up of inorganic ions mixed with nitrogen, phosphorus and carbon, the signature elements of biological matter.
The team demonstrated that both dust and biological material indeed form the nuclei of these ice particles, something that previously could only be simulated in laboratory experiments.
"This has really been kind of a holy grail measurement for us," said Prather.