Long-term trends of tropospheric carbon monoxide and hydrogen cyanide from analysis of high resolution infrared solar spectra

摘要: Abstract Long-term trend and seasonal variation of the mean free tropospheric volume mixing ratios carbon monoxide (CO) hydrogen cyanide (HCN) have been derived from analysis a time series solar absorption spectra recorded US National Solar Observatory on Kitt Peak (31.9°N, 111.6°W, 2.09 km altitude) spanning almost three decades. The results fit to CO 258 daily averages May 1977 April 2005 as function with model that assumes sinusoidal cycle linear long-term yield ratio 102 ± 3 ) parts per billion ( 10 - 9 unit volume) below 10 km altitude, 1 sigma. measurements show maximum in March minimum September an amplitude 22.3 1.5 % relative mean. best-fit corresponds 0.15 0.14 yr , sigma, To quantify possible impact periods intense fires, compared HCN, well-documented emission product biomass burning lifetime ∼ 5 months. best full HCN 208 1978 0.219 0.007 ppbv altitude similar cycle, though lower than for CO. Although same-day enhancements up factor 1.87 1.24 were measured values predicted by accounts cycles trends both molecules, excluding elevated fire emissions has no significant trends. Our result since late 1970s suggests global average decline reported 1990 through 1995 not continued troposphere. Similarly, same yields 2.09–10 km 0.219 ppbv 0.12 1978, also indicating above mid-latitude continental station. molecules suggest site was significantly impacted summer boreal fires during span some years cause widespread pollution northern higher latitude sites.