Ground‐based remote sensing of methane height profiles with a tunable diode laser heterodyne spectrometer

Height distributions of methane in the troposphere and stratosphere were derived from high resolution absorption spectra observed with a ground‐based tunable diode laser heterodyne spectrometer. The center wavenumber of the measured methane absorption line is 1223.1561 cm−1. In the retrieval of methane height profiles, a volume mixing ratio of methane was assumed to have a constant value in the troposphere and to decrease with a constant rate in the stratosphere. The tropospheric mixing ratio and the decreasing rate in stratosphere were derived to be 1.7±0.1 ppmv and −0.06 ppmv/km, respectively, for measurements at Tsukuba (36.0°N, 140.1°E) on December 17 and 20, 1991.