First ground‐based infrared solar absorption measurements of free tropospheric methanol (CH 3 OH): Multidecade infrared time series from Kitt Peak (31.9°N 111.6°W): Trend, seasonal cycle, and comparison with previous measurements

Atmospheric CH 3 OH (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 ν 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 CH 3 OH 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.