Features and trends in Atmospheric Trace Molecule Spectroscopy (ATMOS) version 3 stratospheric water vapor and methane measurements

Mixing ratios of water vapor entering the stratosphere are inferred from Atmospheric Trace Molecule Spectroscopy (ATMOS) measurements to be 3.28 ppm in 1985, 3.53 ppm in 1992, 3.67 ppm in 1993, and 3.65 ppm in 1994, yielding an average increase of 0.041±0.007 (1σ) ppm/yr or 1.2±0.2%/yr between 1985 and 1994. Strong evidence for a seasonal cycle in water vapor is apparent below 45km in the tropics, and ascent rates derived from these tropical profiles are comparable to previous estimates. An enhancement in the sum [H 2 O]+2[CH 4 ] apparent between 45 and 60km in the tropics appears to be consistent with remnants of a seasonal cycle in [H 2 O].