Frequency Comb-Based Remote Sensing of Greenhouse Gases over Kilometer Air Paths
Abstract
We demonstrate coherent dual frequency-comb spectroscopy for detecting variations in greenhouse gases. High signal-to-noise spectra are acquired spanning 5990 to 6260 cm^-1 (1600 to 1670 nm) covering ~700 absorption features from CO2, CH4, H2O, HDO, and 13CO2, across a 2-km open-air path. The transmission of each frequency comb tooth is resolved, leading to spectra with <1 kHz frequency accuracy, no instrument lineshape, and a 0.0033-cm^-1 point spacing. The fitted path-averaged concentrations and temperature yield dry-air mole fractions. These are compared with a point sensor under well-mixed conditions to evaluate current absorption models for real atmospheres. In heterogeneous conditions, time-resolved data demonstrate tracking of strong variations in mole fractions. A precision of <1 ppm for CO2 and <3 ppb for CH4 is achieved in 5 minutes in this initial demonstration. Future portable systems could support regional emissions monitoring and validation of the spectral databases critical to global satellite-based trace gas monitoring.
Keywords
Cite
@article{arxiv.1406.3326,
title = {Frequency Comb-Based Remote Sensing of Greenhouse Gases over Kilometer Air Paths},
author = {Gregory B. Rieker and Fabrizio R. Giorgetta and William C. Swann and Jon Kofler and Alex M. Zolot and Laura C. Sinclair and Esther Baumann and Christopher Cromer and Gabrielle Petron and Colm Sweeney and Pieter P. Tans and Ian Coddington and Nathan R. Newbury},
journal= {arXiv preprint arXiv:1406.3326},
year = {2014}
}