Effects of the 2006 El Nino on tropospheric composition as revealed by data from the Tropospheric Emission Spectrometer (TES)

The Tropospheric Emission Spectrometer (TES) is unique in providing multi-year coincident tropospheric profiles of CO, O-3 and H2O. TES data show large differences in these gases over Indonesia and the eastern Indian Ocean in October-December 2006 relative to 2005. In 2006, O3 was higher by 15-30 ppb (30-75%) while CO was higher by > 80 ppb in October and November, and by similar to 25 ppb in December. These differences were caused by high fire emissions from Indonesia in 2006 associated with the lowest rainfall since 1997, reduced convection during the moderate El Nino, and reduced photochemical loss because of lower H2O. The persistence of the O3 difference into December is consistent with higher NOx emissions from lightning in 2006. TES CO and O3 enhancements in 2006 were larger than those observed during the weak El Nino of 2004.