Ray Nassar, Jennifer Logan, Lee Murray, Lin Zhang, Inna Megretskaia

Harvard University

COSPAR, Montreal, 2008 July 13-19

Investigating Tropical Tropospheric O3 and CO during the 2006 El Niño using TES observations and GEOS-Chem

El Niño Southern Oscillation (ENSO)

Oceanic-Atmospheric phenomenon

warm phase – El Niño

cold phase – La Niña

SST anomalies and changes in ocean circulation induce changes in atmospheric convection, precipitation and chemical composition

… also Indian Ocean Dipole (IOD)

both ENSO & IOD influence Indonesian region, but warm phases rarely coincide: 1963, 1972, 1997 and 2006

http://www.cgd.ucar.edu/cas/

Saji et al. (1999) Nature

5°N-5°S, 170-120°W

Niño 3.4

ENSO

IOD

Ozone during the 1997 El Niño

“Asymmetric Dipole Anomalies”

TOMS Tropospheric Column Ozone (TCO) residual

MLS H2O at 215 hPa

NOAA Outgoing Longwave Radiation (OLR)

http://ggweather.com/enso/nino_regions.gif

Chandra et al. (1998) GRL

O3

H2O

OLR

1997 – 1996 Anomalies

Modeling O3 during the 1997 El Niño

Hauglustaine, Brasseur & Levine (1999) GRL

MOZART model

Sudo & Takahashi (2001) GRL

CHASER model

Trop Column Ozone from TOMS using Convective Cloud Differential technique

Chandra et al. (2002) JGR

GEOS-Chem modelTCO using CCD, TOMSTOMS Aerosol Index for biomass burning

-> Biomass Burning component-> Meteorology/Dynamics/Convection component

Duncan et al. (2003) JGR

GEOS-Chem, focus on biomass burning and lightning

Chandra et al. (2002) JGR

Observations

Model

Tropospheric Emission Spectrometer (TES)

High resolution Fourier Transform Spectrometer (FTS) on Aura, measures nadir IR emission, launched 2004 July 15, ~705 km sun-

sync orbit

GEOS-ChemTropospheric Chemical Transport

Model

Changes to O3 and CO during the 2006 El Niño

TES has well-characterized O3

with ~2 DOFS in the troposphere

and simultaneous coincident CO as proxy for biomass

burning

Logan et al. (2008) GRL

1) Does GEOS-Chem properly simulate CO and O3 distributions during the El Niño?2) How do biomass burning, lightning and transport contribute to enhanced tropospheric CO and O3?3) How can the model simulations be improved?

TES

TES & GEOS-Chem LT CO: October 2006

• TES v02 CO cloud and data quality flag filtered• Constant TES prior based on 30ºS-30ºN July mean• Horizontal 2ºx2.5º, Vertical average of 6 TES levels LT (825-511 hPa)• Differences exceed TES CO biases of ±10%, Luo et al. (2007) JGR

2ºx2.5º resolution

TES & GEOS-Chem LT O3: October 2006

• TES v02 O3 cloud, data quality and emission layer flag filtered• Constant TES prior based on 30ºS-30ºN July mean• Horizontal 2ºx2.5º, Vertical average of 6 TES levels LT (825-511 hPa)• Differences exceed TES O3 biases of 3-10 ppb, Nassar et al. (2008) JGR

2ºx2.5º resolution

2006–2005 CO Differences

October

November

December

GEOS-Chem TES Observations

Biomass Burning impact on CO

TES Observations

GEOS-ChemGFEDv2 2005 &

2006

GEOS-ChemGFEDv2 2005 both

years

October

November

December

GFEDv2 = Global Fire Emissions Database (version 2) 8-day temporal resolution

2006–2005 O3 Differences

October

November

December

GEOS-ChemGFEDv2 2005 &

2006

GEOS-ChemGFEDv2 2005 both

years

TES Observations

Evolution of Indonesian CO plume

ppb

CO and O3 Lower Troposphere (LT) Timeseries

Subtracted 6 ppbv from TES O3 to account for bias determined in validation (Nassar et al., 2008 JGR)

GFEDv2

TES

GEOS-Chem wAKTES

corrected

TES

GEOS-Chem wAK

Global Fire Emission Database v2 Methodology

1) MODIS fire counts (8-day) for timing and spatial

distribution

2) Emission factors for each land type (savanna, tropical forest, temperate forest) and each chemical species

Updated 2006 Lower Trop Timeseries

November GFEDv2 emissions increased 3x to account for smoldering peat fires

GFEDv2

GEOS-Chem & Lightning Imaging Sensor (LIS)

October

November

December

GEOS-Chem 2006 Lightning

Flashrate

GEOS-Chem2006-2005

LIS Observations

2006-2005

Note: Flashrates below a given absolute threshold were omitted for % differences

NOx from lightning reacts with CO or hydrocarbons to form tropospheric O3

Hamid et al. (2001) GRL, discuss lightning enhancement over Indonesia during 1997 El Nino

Updated 2006 Lower Trop Timeseries

Scaling model lightning to

LIS observations improves the O3 timeseries

but

discrepancy remains

TES & GEOS-4 UT H2O comparison with O3 anomalies

Outgoing Longwave Radiation (OLR) from NOAA and GEOS-4

*High OLR = Low Convection

NOAA Indonesian OLR anomalyOLRYYYY – OLRclimatology

From Australian Bureau of Meteorology http://www.bom.gov.au/bmrc/clfor/cfstaff/matw/maproom/index.

htm

NOAA OLR 2006-2005

GEOS-4 OLR 2006-2005

W/m2

W/m2

Summary and Conclusions

• GEOS-Chem can simulate the main CO and O3 features of the 2006 El Niño

• Biomass burning, lightning and transport are all important contributors to enhanced tropospheric O3 during El Niño

• GFEDv2 must account for CO from smoldering fires• GEOS-Chem should move away from climatological

approach to lightning• Improvements to GEOS meteorological fields such as

H2O and deep convection fields will result in better simulations of atmospheric composition

Acknowledgments: Work was funded by a NASA grant to Harvard University