Altitude profiles of Carbon Monoxide (CO) and aerosols have been compared from the Network for Stratospheric Change (NDSC) mid-latitude southern hemisphere site at Lauder, New Zealand. The CO mixing ratio profile was derived from infrared spectra recorded with a very high resolution Fourier Transform interferometer using three lines of the (1-0) band between 2057 and 2160 cm-1. The aerosol surface area was derived from balloon-borne backscatter radiation at 940 nm. Both datasets show significant enhancements occurring over the observation site in the austral spring. When displayed together their combined effect illustrates the close correlation between CO and aerosols. Peak concentrations are consistently recorded between September and October over a five year time frame (1994--1999), with the enhancements typically occurring at heights of between 3 to 8 km. The temporal and spatial correlation between the aerosol plumes and enhanced CO concentrations are interpreted in terms of the effect of long range transport of biomass burning plumes in combination with the El Nino-Southern Oscillation (ENSO) cycles influence on southern hemisphere climate dynamics. ¿ 2001 American Geophysical Union