Carbon dioxide observations at Izaña baseline station, Tenerife (Canary Islands): 1984—1988

Atmospheric carbon dioxide concentrations have been monitored at Izaña Observatory (Tenerife, Canary Islands) during 1984—88. Because of its position on top of a mountain plateau at 2367 m above sea level, the sampled air at this baseline station is usually representative of the free troposphere in the southern part of the North Atlantic. A criterion to select those half-hourly values representative of baseline conditions is established and from these selected data, daily means are calculated. Oscillations produced by different synoptic situations still remain in the selected record and its power spectrum shows a hint of significant frequencies in the typical synoptic range. A low-pass filter with a cutoff frequency of 2 months was used to obtain a record free from synoptic influences representing “background” air and yielding a mean annual cycle with a peak-to-peak amplitude of approximately 7 ppmv.