QBO and QTO of the atmospheric trace element carbon monoxide during 1989–2001: An update

An analysis of the 12-month running means of CO (carbon monoxide) concentrations at various latitude belts during the 13 years 1989–2001 indicated oscillations with peak spacings in the QBO, QTO (quasi-biennial and quasi-triennial oscillations, 2–3 and 3–4 year) ranges. For middle and high northern latitudes, the QBOs of CO almost resembled the QBO of stratospheric low latitude winds. For other latitudes, there was no similarity with stratospheric winds. CO had a significant QTO in the range 3.0–3.3 years, but it did not match well with the major periodicity of ENSO (El Niño/Southern oscillation) at 4.3 years. The relative importance of the two mechanisms proposed by Hamilton and Fan [Journal of Geophysical Research 105 (2000) 20581–20587], namely the transport mechanism (dynamic stratospheric QBO modulating the interannual variations of long-lived tropospheric constituents) and the ozone mechanism (stratospheric QBO, affecting stratospheric ozone, affecting the UV radiation filtering down, affecting OH radical in the troposphere, affecting CO) is discussed. Both mechanisms seem to be partly operative in some latitudes.