First ground-based infrared solar absorption measurements of free tropospheric methanol (CH3OH): Multidecade infrared time series from Kitt Peak (31.9°N 111.6°W): Trend, seasonal cycle, and comparison with previous measurements

摘要

Atmospheric CH_3OH (methanol) free tropospheric (2.09-14-km altitude) time series spanning 22 years has been analyzed on the basis of high-spectral resolution infrared solar absorption spectra of the strong V_8 band recorded from the U.S. National Solar Observatory on Kitt Peak (latitude 31.9°N, 111.6°W, 2.09-km altitude) with a 1-m Fourier transform spectrometer (FTS). The measurements span October 1981 to December 2003 and are the first long time series of CH3OH measurements obtained from the ground. The results were analyzed with SFIT2 version 3.93 and show a factor of three variations with season, a maximum at the beginning of July, a winter minimum, and no statistically significant long-term trend over the measurement time span.