Aerosol extinction measurements are crucial to understanding the effects of atmospheric particles on ozone depletion (stratosphere), radiation (stratosphere and troposphere), visibility (troposphere) and public health (boundary layer). Despite the acute need, no existing instrument can measure direct, in situ aerosol extinction profiles from the ground to the mid-stratosphere. Satellite-based instruments, including NASA’s new Stratospheric Aerosol and Gas Experiment III-ISS, report extinction globally but are currently validated by indirect measurements with ~40% uncertainty. This uncertainty could be eliminated by measuring extinction directly with the balloon-borne Open-path Cavity Ringdown Spectrometer (BOPCRDS) we will develop in this project. The BOPCRDS (expected precision is 0.05 Mm-1) will cost <$25,000, and its open-path configuration will enable it to measure ambient extinction (rather than extinction from dried particles or estimated from size distribution measurements) from 0-30 km altitude, thereby significantly advancing the current state-of-the-art. During Phase I we will (1) design and build the BOPCRDS, (2) test it at -60 degrees Celsius and on a vibration table, (3) compare measurements against theory using gases with known extinction cross-sections, (4) deploy it during a SAGE III-ISS overpass and demonstrate its utility for satellite validation by comparing its measurements against the current state-of-the-art instruments. In Phase II, we will develop a multi-wavelength, miniature BOPCRDS with expanded dynamic range and target price of $5,000. Increased dynamic range could make the BOPCRDS useful for measuring stratospheric aerosol during volcanically active periods and tropospheric profiles in polluted regions.
This technology supports NASA’s efforts to improve understanding of the Earth’s radiation balance and predict climate changes. By supporting this project, NASA would obtain measurement capabilities that would support model validation efforts. In Phase II, we will develop a multi-wavelength, miniature BOPCRDS with expanded dynamic range and target price of $5,000. Increased dynamic range could make the BOPCRDS useful for measuring stratospheric aerosol during volcanically active periods and tropospheric profiles in polluted regions.
The BOPCRDS will be invaluable for validating instruments at DOE’s ARM facility--a need recently stated by DOE. It could also reduce the necessity for costly, manned airborne science flights and will be attractive to researchers studying the Asian Tropical Aerosol Layer (ATAL) and those studying the impact of volcanoes on stratospheric aerosol.