Csu Atmospheric Scientist Studies Particulates, How Clouds Form in Skies Above Colorado, Wyoming

Note to Editors: Photos of Professor Paul DeMott are available with the news release at http://www.newsinfo.colostate.edu/.

The air gets a little thin at 25,000 feet above south-central Colorado, but that makes it ripe for the picking for Colorado State University atmospheric researcher Paul DeMott.

Since the end of October, DeMott has been grabbing air samples out of the skies above Colorado to study how certain tiny particles form ice in clouds as far south as the New Mexico border and as far north as north-central Wyoming. He’s part of a select group of scientists flying out of Rocky Mountain Metropolitan Airport in Jefferson County in a specially equipped C-130 aircraft owned by the National Science Foundation (NSF) and operated by the National Center for Atmospheric Research (NCAR).

The National Science Foundation-funded project to study cloud formation processes ends in mid-December.

Ultimately, the research could improve climate modeling, helping scientists predict with more certainty where and how clouds and precipitation form and the impact of changing atmospheric composition on clouds. Special particles called ice nuclei result from desert dusts, from some biological processes and possibly from pollution, which are needed to form ice in clouds. Scientists have spent decades trying to understand the processes.

"If we can measure these particulates and how they make ice, can we predict exactly how ice will form in the ideal cloud?" DeMott said, noting that, for now, CSU is the only university with an instrument to take continuous air samples from in and around clouds and measure in real time the ice-forming ability of particles inside a plane. "We need to understand all the mechanisms for first forming ice. Then we can identify the nature of other processes we don’t understand that don’t have anything to do with particulates – processes that cause the amount of ice to multiply, for example."

As part of the NSF grant, CSU and other scientists have temporarily retrofitted the C-130 with their equipment. They’ve spent two to five days a week since October flying about five hours a day to study clouds. Fall provides ideal weather for studying ice formation in clouds forming over the mountains and Front Range that contain smooth air flow, also known as wave or lenticular clouds. The field campaign, called the Ice in Clouds Experiment, is led by NCAR scientist Andrew Heymsfield.

DeMott, working with two other CSU research scientists and two postdoctoral researchers, is the principal investigator on a three-year, $650,000 NSF grant he obtained in 2006. On the NCAR plane, he and his CSU team take air samples into a small chamber through a special port on the side of the plane. A diffusion chamber cools and humidifies the air and particles between two plates of ice toward conditions where ice forms – essentially allowing DeMott to "grow" clouds by simulating the conditions in the atmosphere. He then evaluates how many particles will form ice crystals for specific cloud conditions. The C-130 then passes through the wave clouds to measure, with other instruments, how much ice really does form. DeMott and other investigators also use specialized instruments to determine the chemical makeup of the particulates forming ice.

Earlier this year, his grant took him to Japan in trans-Pacific flights on another NSF study of how dust and pollution from Asia travels as far east as the United States and beyond. While the particles are released at the planet’s surface, they ultimately move across the planet multiple times when storms loft them to higher altitudes, DeMott said. His research looked at the quantity of ice nuclei and their changes in the time and distance from their source. He expects to publish that research in a peer-reviewed journal within the next six months.

DeMott is a senior research scientist in the Atmospheric Chemistry Group in the Department of Atmospheric Science, which has been designated by the university as a Program of Research and Scholarly Excellence. The department has been recognized internationally for its work on such major projects as CloudSat, the world’s first cloud-profiling radar in orbit, and is home to two University Distinguished Professors, Graeme Stephens and Tom Vonder Haar.