# Presentation: 169140

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

**S. Chandra****1,2****, J. R. Ziemke****1,2****, B. N. Duncan****1,2****, and T. N. Diehl****1,2**
**                                                                                                     **** ****                                                           ****1****Goddard Earth Sciences and Technology, Univ. of Maryland Balt. Co., Baltimore, MD, USA**
**                                                                                                                                                                 ****2****NASA Goddard Space Flight Center, Greenbelt, MD, USA**
**	****	****                                   ****Contact: **_[Jerald.R.Ziemke@nasa.gov](mailto:Jerald.R.Ziemke@nasa.gov)_

_**Abstract**_

**An important indicator of biomass burning and precursor of O3 production is CO.  ****Figures 2a and 2b**** show changes in upper tropospheric CO from MLS (top) and GMI (bottom) for October and December months.  ****Figure 2**** is similar to ****Figure 1**** for O3 except that upper tropospheric CO is plotted instead.  In October the measurements and  model both show that the El Niño induced changes in CO were very intense in the western Pacific, but that these increases in year 2006 were also highly localized to the Indonesian region.  The intense concentrations of CO over Indonesia in October 2006 were nearly gone by December as seen in both the GMI model and MLS measurements (****Figure 2b****).**

_**OMI/MLS Data and the GMI Model**_

_**Conclusions**_

**observed characteristics of O3 and H2O inferred from previous El Niño events.  The changes during the 2004 El Niño in tropospheric O3 and H2O from TES are similar to those inferred from the Ozone Monitoring Instrument (OMI) and Microwave Limb Spectrometer (MLS) flown on the same Aura satellite [*****Chandra et al*****., 2007].**
**The El Niño related changes in tropospheric O3 in 2006 are discernible in ****Figures 1a and 1b****.  These figures show differences in OMI/MLS O3 (top panels) and GMI O3 (bottom panels) between the years of 2006 (El Niño year) and 2005 (non-El Niño year).  **
**During El Niño years the eastward shift in warm sea surface temperature (SST) produces planetary scale change in tropical convection which reduces O3 in the eastern Pacific and increases O3 in the western Pacific.  ****Figure 1a**** for both model and OMI/MLS shows largest increases of O3 over Indonesia which will be shown later from the GMI model to be caused in part by biomass burning.  ****Figure 1b**** for December shows that the patterns for model and observations are also well in agreement, but very different than for October.  Most of the changes for December including the large depression of O3 over eastern Africa are of dynamical origin.  **
**The GMI model indicates that the reduced O3 over eastern Africa comes from changes in O3 induced by changes in transport affecting O3 in the upper troposphere.  Most changes in ****Figures 1a and 1b**** in the model are primarily evenly balanced between upper troposphere (above 500 hPa) and lower troposphere (below 500 hPa).**

- (Figure 1a)

_**El Niño-Induced Biomass Burning CO**_

- (Figure 1b)

- (Figure 2a)

- (Figure 2b)

**We have compared El Niño related changes in tropospheric O3 and CO in 2006 using both the GMI model and OMI/MLS measurements.  The GMI model was analyzed to estimate the relative importance of biomass burning and large-scale transport in producing the El Niño related changes in tropospheric O3.  Our approach is similar to the one used by *****Chandra et al*****. [2002, JGR] in analyzing the effects of the 1997 El Niño on tropospheric O3.  The GMI model in this study was run in two modes: **
**(1)  The first mode explicitly included NOx aned CO emission rates associated with the Indonesian fires.**
**(2)  In the second mode, the model was run by excluding the contributions from the Indonesian fires.**
**These two model runs were used to assess the effects of biomass burning and large-scale transport on tropospheric O3 as shown in ****Figure 3**** for the month of October 2006 relative to October 2005.    The**

- (Figure 3)

**Recently *****Logan et al*****. [2008] studied the effects of the 2004 and 2006 El Niño events on tropospheric profiles of CO, O3, and H2O measured from the Tropospheric Emission Spectrometer (TES) flown on the Aura satellite.  Their findings were generally consistent with the**

**We have studied the effects of the 2006 El Niño on tropospheric O3 and CO at tropical and sub-tropical latitudes measured from the OMI and MLS instruments on the Aura satellite.  The 2006 El Niño induced a severe drought which caused large-scale fires (set to clear land) to burn out of control during October and November months in the Indonesian region.  The effects of these fires are clearly seen in the enhancement of CO concentration measured from the MLS instrument.  We have used a global model of atmospheric chemistry and transport (GMI CTM) to quantify the relative importance of biomass burning and transport in producing observed changes in tropospheric O3 and CO.  The model results show that during October and November months both biomass burning and meteorological changes contributed almost equally to the observed increase in tropospheric O3 over Indonesia.  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 Dobson Units (DU) but it covered a much larger area in the Indian Ocean and western Pacific extending from south east Asia in the north to western Australia in the south.  By December 2006 the effect of biomass burning was reduced to zero and the observed changes in tropospheric O3 were mostly due to dynamical effects.**

**Tropospheric O3 derived from Aura OMI and MLS is discussed by *****Ziemke et al.***** [2006, JGR].  Version 8.5 (“collection 3”) total O3 from OMI is combined with MLS v2.2 stratospheric column O3 to derive residual tropospheric column O3.  Validation of MLS O3 and CO is described by *****Froidevaux et al.***** [2008, JGR] and *****Livesey et al.***** [2008, JGR], respectively.  These satellite measurements of tropospheric O3 and CO are evaluated one-to-one with the same trace gases as simulated by the Global Modeling Initiative (GMI) chemical transport model.  The GMI combined stratosphere-troposphere model is described by *****Duncan et al.***** [2008, JGR, and references therein].**

_**El Niño-Induced Changes in O3**_

_**Impact of Biomass Burning on O3**_

**impact from biomass burning was estimated by subtracting tropospheric O3 generated from the second model run from the first model run.  The impact from dynamical forcing was determined from the second model run without the Indonesian emissions.**
**The GMI model for October 2008 (****Figure 3****) suggests that the effect on tropospheric O3 from biomass burning  during the 2006 El Niño event  generated sizeable increases in O3, but these increases were localized to the vicinity of biomass burning  in Indonesia.  Most of the inter-annual changes in tropospheric O3 in the tropics extending to the subtropics in October 2006 was caused by dynamical forcing.  The study by *****Logan et al.***** [2008] using Aura TES measurements attributed most increases in tropospheric O3 in the western Pacific in 2006 to differences in the magnitude of CO emissions from fires in Indonesia.  They suggested a significant contribution from NOx production due to lightning in late November and December 2006 when CO production due to large scale forest fires** **decreased significantly.**
**The GMI model for October indicates that the increases in tropospheric O3 caused by biomass burning is around 4-6 DU.  The bottom panel of ****Figure 3**** shows that these increases are comparable to about 4-8 DU increases throughout much of the western Pacific caused by changes in meteorological conditions.  The GMI results for November (not shown) are similar to October.  By December the biomass burning contribution is essentially nonexistent.**

_**Conclusions**_

**We have compared induced changes in tropospheric O3 and CO from the GMI model and Aura OMI/MLS measurements for the El Niño event of 2006.  The El Niño-induced temporal changes and spatial distributions of these trace gases from the model and observations show remarkable similarities.**
**The drought conditions in Indonesia during the 2006 El Niño event produced intense biomass burning over the region which generated tropospheric O3.  The GMI model suggests that the amount of tropospheric O3 generated from biomass burning was substantial (~4-6 DU) but localized to the Indonesian region.  Most increases in tropospheric O3 in the western Pacific during the El Niño of 2006 were of dynamical origin rather than biomass burning.**