Combined influences of water vapor, ozone, aerosols and cirrus clouds in the upper-troposphere/lower-stratosphere (UTLS) region serve to strongly modulate radiative forcing of the earth's climate system. The composition of this region is affected not only by chemical processes, but also by dynamical ones such as cross-tropopause exchange and convective transports originating near the earth's surface. The Deep Convective Clouds and Chemistry (DC3) field campaign, to be conducted May-June 2012, will support study of the contrasting impacts of continental midlatitude thunderstorm systems on UTLS composition and chemistry within three regions (viz. northeastern Colorado, western Oklahoma and Texas, and northern Alabama) characterized by differing background chemistry and characteristic storm behavior. This award will support adaptation of an existing tunable diode laser-based instrument, the University of Colorado closed-path laser hygrometer, to make measurements of total water (from which condensed liquid and ice water contents may be derived) aboard the NSF/NCAR GV research aircraft during DC3. A new inlet specific to the selected sampling location aboard the GV will be designed and built in collaboration with a consultant from Embry-Riddle Aeronautical University to enable accurate sampling of a wide range of cloud particle sizes (10-400 micrometers).
The intellectual merit of this research rests on provision of precise and accurate measurements of total water at high spatial resolution within the upper reaches of midlatitude convective cloud systems, which will in-turn allow investigators to describe differing transport properties of shear-driven vs. airmass-type thunderstorms, their attendant evolving microphysical properties over cloud lifecycles, and how anvil radiative environments differ from region to region and with time during the interval 12-48 hours after cessation of active convection. Broader impacts will include graduate student training and public outreach, but will ultimately extend to improved understanding of controls on atmospheric ozone and associated links to climate assessment and policy formulation.
