The carbon monoxide tape recorder

Using Aura MLS data we have identified the stratospheric ‘tape recorder’ in carbon monoxide (CO). Unlike the water vapor tape recorder, which is forced by the upper tropospheric seasonal variation in dehydration processes, the CO tape recorder is linked to seasonal changes in biomass burning. Since CO has a chemical lifetime of only a few months, the CO tape recorder barely extends above 20 km. The tape head for CO appears to be close to 360 K near the same location as the water vapor tape head (Read et al., 2004). Both tape heads are below the equatorial cold point tropopause but above the base of the tropical tropopause layer. The Global Modeling Initiative chemical transport model forced by the climatology of biomass burning reproduces the CO tape recorder. The tape recorder signal in the GMI model becomes more distinct from 360 K to 380 K suggesting that convective detrainment plays a decreasingly important role with altitude.