Analytical Chemistry Seminar: Dr. Andrew Rollins
Jointly sponsored by the Department of Chemistry and Biochemistry, CIRES, and the Environmental Program
Chemical and Physical Processes Controlling Organic Aerosols and Tropopause Cirrus: An Observational Perspective
Dr. Andrew Rollins, NOAA Chemical Sciences Division
Condensed mass in the atmosphere in the form of aerosol and cloud particles is a significant driver of climate and heterogeneous atmospheric chemistry. The processes that control the formation of these particles are complex, and understanding them is frequently limited by the ability to accurately measure the gas and particulate species required to test our theories. In this talk I will discuss results from two recent projects where new analytical instrumentation has been developed and used to inform our understanding of gas/particle partitioning processes involving organic aerosols and cirrus clouds. The first study presented exploits high time resolution measurements of organic nitrate aerosols using a laser induced fluorescence based technique. Laboratory and field measurements using this instrument have been used to probe the influence of nitrogen oxide chemistry on the formation of secondary organic aerosols (SOA) in the troposphere. Observations during the California Nexus (CalNex) field study demonstrate the significance of nitrate radical initiated SOA formation at night, and important nonlinearities in this chemistry.
In the second half of the talk I will discuss measurements of water vapor and ice water content in the tropical tropopause layer (TTL) using a new tunable diode laser based hygrometer operated on the NASA Global Hawk aircraft. Confidence in the accuracy of these historically challenging measurements is strengthened by use of an in-situ calibration system, and excellent agreement with a separate hygrometer operated in parallel. These measurements have provided evidence for the transport of water in excess of saturation through the TTL and into the stratosphere.