Open Path, Aircraft-Based Ammonia Instrument using a Quantum Cascade Laser and Singular Valued Decomposition Algorithms

79517S The largest uncertainty in global climate change is the effects of aerosols, and it is critical that aerosol processes are well quantified in order to assess anthropogenic influences on climate. Ammonia is an important species in aerosol particle nucleation, growth, composition, and acidity. Unfortunately, fast ammonia measurements are scarce due to difficulty in sampling, especially from aircraft, even though 80% of ammonia sources are anthropogenic. This project will develop an open-path, airborne instrument capable of measuring tropospheric levels of ammonia using a continuous wave quantum cascade laser and singular valued decomposition algorithms. The instrument will measure ammonia every second, occupy the space of a shoe box, and have a resolution of 20 parts per trillion by volume. Phase I will focus on the performance characteristics of a quantum cascade laser and the testing of singular valued decomposition methods to reduce etalon noise. A 50 m, multiple pass optical cell will be used to acquire spectra of absorbing features in and around the ammonia absorption band. The ultimate noise level obtained using wavelength modulation spectroscopy and singular valued decomposition will provide a basis for Phase II. Commercial Applications and Other Benefits as described by the awardee: A fast, airborne ammonia instrument should greatly enable studies of particle nucleation and particle composition in both clean and polluted regions. Data obtained from the instrument will help predict aerosol formation rates in both urban and remote environments and ultimately help quantify anthropogenic activities on climate. The instrument also should have numerous applications in atmospheric chemistry field campaigns, regional air networks, and pollution monitoring. Other applications include the semiconductor industry, where ammonia poisons the photocatalytic doping process, and medicine, to diagnose renal diseases by measuring trace ammonia exhaled in breath.