Laser Spectroscopic Studies of Atmospheric Cooling and Heating Processes
Our group is interested in cooling and heating mechanisms in Earth's upper atmosphere. We use laser spectroscopy to measure rate coefficients of relevant energy transfer processes contributing to these heating and cooling processes. Accurate knowledge of the important rate coefficients will be necessary to correctly interpret data being acquired by NASA's SABER experiment, which is part of the ongoing TIMED satellite mission. These are also crucial input parameters in the aeronomic models being used to track long-term climate change.
The dominant cooling mechanism in the mesosphere and lower thermosphere involves vibrational excitation of carbon dioxide by collision with atomic oxygen followed by relaxation of the carbon dioxide through spontaneous emission of infrared radiation. Much of this radiation escapes into space, thereby removing ambient kinetic energy from the atmosphere and accomplishing a local cooling effect. We are measuring the efficiency of this vibrational energy transfer process using transient diode laser absorption spectroscopy in the mid-infrared spectral region. Rate coefficients are being measured over the range of temperatures encountered in the relevant region of the atmosphere.
Ozone is involved with up to 80% of the heating processes in the mesosphere and lower thermosphere, yet ozone kinetics have not been studied to a great extent because the experiments are difficult. However, a detailed understanding of the kinetics and dynamics with which ozone exchanges energy with its surroundings is necessary to accurately model the upper atmosphere. We plan to perform experiments similar to those used in our carbon dioxide-O studies to measure the kinetics of ozone-O interactions
Karen J. Castle
Department of Chemistry,