Zonal asymmetries in southern hemisphere column ozone: Implications of biomass burning

This study compares Nimbus 7 total ozone mapping spectrometer (TOMS) total column ozone with ozone data from two different satellite instruments measuring vertical profiles of ozone in the stratosphere. The first instrument is the microwave limb sounder (MLS) onboard the upper atmosphere research satellite (UARS) and the second is the solar backscattered ultraviolet (SBUV2) nadir sounder aboard NOAA 11. Previous studies have shown that TOMS data exhibit a zonal wave maximum (amplitudes similar to 20-30 Dobson units) in total column ozone in the tropical South Atlantic region near 0 degrees longitude. This wave structure occurs in all seasons but maximizes around August-October in association with intense biomass burning in South America and southern Africa. Results of this investigation show that MLS stratospheric column ozone integrated between 1 to 68 hPa shows no such feature. Horizontal structures of 1 to 68-hPa MLS column ozone are found to be incoherent with TOMS and SBUV2 total column data in the tropics in all seasons. This study provides the first evidence from a UARS data set that the southern tropical wave 1 peak in TOMS may have relatively small dependence on stratospheric ozone. Combined MLS, TOMS, SBUV2, and ozonesonde station data show that zonal asymmetries observed in total column ozone in the tropics originate primarily from tropospheric effects (dynamics coupled with biomass burning). Outside of the tropics, zonal patterns in total ozone originate mostly from stratospheric dynamics. Wave signatures in TOMS, SBUV2, and MLS column ozone all show generally coherent horizontal structures in middle and high latitudes, especially during seasons of large planetary wave events such as in the southern hemisphere during southern winter-spring.