The Chemistry of a Thunderstorm
Date Posted: May 16, 2012
May 15 marks the beginning of a large-scale, comprehensive field project to measure how thunderstorms transport, produce and process chemicals that form ozone, a greenhouse gas that affects Earth's climate, air quality and weather patterns.
During the 45-day Deep Convective Clouds and Chemistry (DC3) project, more than 100 researchers from NOAA and 29 other organizations, including lightning experts and atmospheric chemists, will use research radars, weather balloons and specially-equipped aircraft to measure changes in the atmospheric chemistry before, during and after thunderstorms.
Thunderstorms act like elevators; their updrafts loft pollution and moisture-rich air to the upper atmosphere where they mix or chemically react in sunlight to produce ozone.
"Usually, these kinds of chemical reactions just simmer along slowly in the upper troposphere," said Tom Ryerson, research chemist with the NOAA Earth System Research Laboratory. "These storms have the potential to crank up reaction rates to more of a boil."
Lightning has a role too. Researchers believe lightning is the largest natural source of a variety of nitrogen-based chemical compounds known as NOx that contribute to ozone concentrations.
This study should provide measurements of these two kinds of ozone formation, providing important insights into the origins of ozone in the upper part of the atmosphere.
The DC3 project will collect data in the diverse weather environments of northern Alabama, northeastern Colorado and central Oklahoma where research facilities already have similar weather instruments. The three research aircraft will be centrally located in Kansas to deploy quickly to a targeted storm.
The NOAA National Severe Storms Laboratory and The University of Oklahoma will provide the ground-based facilities for DC3. NSSL will operate a mobile Doppler radar, four instrumented minivans, and launch balloon borne instruments into storms to measure electric fields, the type and number of precipitation particles, winds, temperature, humidity and pressure.
"This information will improve our understanding of how storms produce lightning," said Don MacGorman, NSSL scientist. "It will help us learn how to use lightning mapping data to improve storm forecasts and warnings."
Lightning mapping arrays operated by OU, NSSL, Texas Tech University and NASA will provide the location, size, and frequency of lightning in storms to go with aircraft measurements of atmospheric chemicals so that they can determine how much NOx lightning produces.
When a thunderstorm breaks up, the observations won't end. Owen Cooper and Jerome Brioude, both with the NOAA Earth System Research Laboratory and the NOAA Cooperative Institute for Research for Environmental Sciences at the University of Colorado, will use weather forecasting models to understand where the air lofted into the troposphere by a thunderstorm travels. A day later, one of the research airplanes will target that region, so scientists can look at how the air mass composition changed: how much ozone formed during the last 24 hours, for example, and whether chemical reactions created particulate matter, too.
The DC3 project runs from May 15-June 30, and is funded by the National Science Foundation, NOAA and NASA. The scientists leading the project are from the National Center for Atmospheric Research, Pennsylvania State University, Colorado State University, and NOAA.