Effects of the 2006 El Niño on tropospheric ozone and carbon monoxide: implications for dynamics and biomass burning

S. Chandra, J. R. Ziemke, B. N. Duncan, T. L. Diehl, N. J. Livesey, L. Froidevaux
2009 Atmospheric Chemistry and Physics  
We have studied the effects of the 2006 El Nifio on tropospheric 0 3 and GO at tropical and sub-tropical latitudes measured from the OM1 and MLS instruments on the Aura satellite. The 2006 El Niiio-induced h u g h t allowed forest fires set to clear land to burn out of conh-ol during October and November in the Indonesian region. The effects of these fires are clearly seen in the enhancement of GO concentration measured from the MLS instrument. We have used a global model of atmospheric
more » ... atmospheric chemistry and h-ansport (GMI CTM) to quantify the relative irrrportance of biomass burning and large scale transport: in producing observed changes in tropospheric O3 and 6 0 . The model results show that during October and November both biomass burning and meteorological changes cofllributed almost equally to the obsemed increase in tropospheric Q3 in the Indonesian region. The biomass component was 4-6 DU but it was limited to the Indonesian region where the fires were most intense, The dynamical component was 4-8 DU but it covered a much larger area in the Indian Ocean extending from South East Asia in the nordh to western Australia in the south. By December 2006, the effect of biomass taming was reduced to zero and the obsemed changes in tropospheric O3 were mostly due to dynamical effects. The model results show an increase of 2-3% in the global burden of tropospheric ozone. In comparison, the global burdean of GO increased by 8-12%. https://ntrs.nasa.gov/search.jsp?R=20080047927 2020-07-10T07:58:46+00:00Z El Niiio and La Niiia events are major sources of inter-annual and decadal variability in tropical tropospheric ozone (a3) [e.g., Ziemke et al. 30031. The atmospheric effects of El Nifio events are generally a change in convection in the tropical troposphere associated with an eastward shift of the warm SST anomaly and large scale Walker circulation. This shift results in an increase in tropospheric column O3 in the western Pacific and a decrease in the eastern Pacific relative to non-El Niiio years. The effect of El Niiio on specific humidity is usually opposite to that of column ozone [ e.g., Chandrcz et al., 1998; 20071. During La Nifia years, dynamical processes are largely reversed which results in a decrease (increase) of column ozone (specific humidity) in the western Pacific, The effects of El Nifio on tropospheric composition have been extensively studied from both satellite and ground based measurements [e.g., ChancIrc~ et al., 1998; Fujiwara et al., 1999; T?~ompson et al., 20011 and by using global models of atmospheric chemistry and transport [e.g.
doi:10.5194/acp-9-4239-2009 fatcat:oa42k6npfvftzfqp3dxygt5ggu