A New ENSO Index Derived from Satellite Measurements of Column Ozone

Abstract. Column Ozone measured in tropical latitudes from Nimbus 7 total ozone mapping spectrometer (TOMS), Earth Probe TOMS, solar backscatter ultraviolet (SBUV), and Aura ozone monitoring instrument (OMI) are used to derive an El Nino-Southern Oscillation (ENSO) index. This index, which covers a time period from 1979 to the present, is defined as the "Ozone ENSO Index" (OEI) and is the first developed from atmospheric trace gas measurements. The OEI is constructed by first averaging monthly mean column ozone over two broad regions in the western and eastern Pacific and then taking their difference. This differencing yields a self-calibrating ENSO index which is independent of individual instrument calibration offsets and drifts in measurements over the long record. The combined Aura OMI and MLS ozone data confirm that zonal variability in total column ozone in the tropics caused by ENSO events lies almost entirely in the troposphere. As a result, the OEI can be derived directly from total column ozone instead of tropospheric column ozone. For clear-sky ozone measurements a +1 K change in Nino 3.4 index corresponds to +2.9 Dobson Unit (DU) change in the OEI, while a +1 hPa change in SOI coincides with a −1.7 DU change in the OEI. For ozone measurements under all cloud conditions these numbers are +2.4 DU and −1.4 DU, respectively. As an ENSO index based upon ozone, it is potentially useful in evaluating climate models predicting long term changes in ozone and other trace gases.

[1]  J. Herman,et al.  Tropical tropospheric ozone and biomass burning. , 2001, Science.

[2]  K. Aikin,et al.  Modulation of middle and upper tropospheric ozone at northern midlatitudes by the El Niño/Southern Oscillation , 1998 .

[3]  Pawan K. Bhartia,et al.  Tropospheric Ozone Determined from Aura OMI and MLS: Evaluation of Measurements and Comparison with the Global Modeling Initiative's Chemical Transport Model , 2006 .

[4]  J. Ziemke,et al.  Quasi-biennial oscillation and tropical waves in total ozone , 1994 .

[5]  K. Bowman,et al.  Effects of the 2006 El Niño on tropospheric composition as revealed by data from the Tropospheric Emission Spectrometer (TES) , 2008 .

[6]  J. Lelieveld,et al.  University of Groningen Identification of an El Niño‐Southern Oscillation signal in a multiyear global simulation of tropospheric ozone , 2007 .

[7]  M. Newchurch,et al.  Lower‐Tropospheric Ozone (LTO) derived from TOMS near mountainous regions , 2001 .

[8]  S. Kawakami,et al.  Tropospheric ozone enhancements during the Indonesian Forest Fire Events in 1994 and in 1997 as revealed by ground‐based observations , 1999 .

[9]  P. Bhartia,et al.  A 25‐year data record of atmospheric ozone in the Pacific from Total Ozone Mapping Spectrometer (TOMS) cloud slicing: Implications for ozone trends in the stratosphere and troposphere , 2005 .

[10]  F. Downton,et al.  Introduction to Mathematical Statistics , 1959 .

[11]  P. Levelt,et al.  Ozone mixing ratios inside tropical deep convective clouds from OMI satellite measurements , 2008 .

[12]  Kevin E. Trenberth,et al.  The Definition of El Niño. , 1997 .

[13]  J. Pyle,et al.  Influence of El Niño Southern Oscillation on stratosphere/troposphere exchange and the global tropospheric ozone budget , 2005 .

[14]  R. Martin,et al.  Quantification of the factors controlling tropical tropospheric ozone and the South Atlantic maximum , 2007 .

[15]  Ricardo Todling,et al.  The GEOS-5 Data Assimilation System-Documentation of Versions 5.0.1, 5.1.0, and 5.2.0 , 2008 .

[16]  Robert V. Hogg,et al.  Introduction to Mathematical Statistics. , 1966 .

[17]  Steven Pawson,et al.  A case study of excessive subtropical transport in the stratosphere of a data assimilation system , 2004 .

[18]  T. Diehl,et al.  Effects of the 2006 El Niño on tropospheric ozone and carbon monoxide: implications for dynamics and biomass burning , 2009 .

[19]  R. Martin,et al.  Space‐based constraints on the production of nitric oxide by lightning , 2007 .

[20]  Steven Pawson,et al.  Goddard Earth Observing System chemistry‐climate model simulations of stratospheric ozone‐temperature coupling between 1950 and 2005 , 2008 .

[21]  R. Martin,et al.  Tropical tropospheric ozone: Implications for dynamics and biomass burning , 2002 .

[22]  J. Gerring.  A case study , 2011, Technology and Society.

[23]  Hennie Kelder,et al.  Variability in tropical tropospheric ozone: Analysis with Global Ozone Monitoring Experiment observations and a global model , 2003 .

[24]  K. Sudo,et al.  Simulation of tropospheric ozone changes during 1997–1998 El Niño: Meteorological impact on tropospheric photochemistry , 2001 .

[25]  M. Ern,et al.  Wave fluxes of equatorial Kelvin waves and QBO zonal wind forcing derived from SABER and ECMWF temperature space-time spectra , 2009 .

[26]  Pawan K. Bhartia,et al.  Two new methods for deriving tropospheric column ozone from TOMS measurements: Assimilated UARS MLS/HALOE and convective‐cloud differential techniques , 1998 .

[27]  Robert J. D. Spurr,et al.  Evaluation of the OMI cloud pressures derived from rotational Raman scattering by comparisons with other satellite data and radiative transfer simulations , 2008 .

[28]  Jennifer A. Logan,et al.  An analysis of ozonesonde data for the troposphere : recommendations for testing 3-D models and development of a gridded climatology for tropospheric ozone , 1999 .

[29]  William G. Read,et al.  Effects of 1997–1998 El Niño on tropospheric ozone and water vapor , 1998 .

[30]  S. Chandra,et al.  La Nina and El Nino—induced variabilities of ozone in the tropical lower atmosphere during 1970–2001 , 2003 .