Tropical Mid-Tropospheric CO2 Variability driven by the Madden-Julian Oscillation

King-Fai Li1, Baijun Tian2, Duane E. Waliser2, Yuk L. Yung1

1 California Institute of Technology, Pasadena2 Jet Propulsion Laboratory, Pasadena

Special Thanks to Dr. Peter Bechtold (ECMWF)Li et al. (2010), PNAS 107, 19171

Motivation

Chahine et al. [2008]

AIRS CO2 (~5 km) reveals influences from circulations Surface sources appearing in mid-troposphere

Convection and stratosphere-troposphere exchangeJet-streams, synoptic weather systems

How does tropical dynamics matter? [A54D-02: ENSO]

Dominant form of intraseasonal variability in the tropics

Strongest during boreal winters Slow (~5 m/s) eastward-propagatin

g oscillations in tropical deep convection and large-scale circulation

Life cycle ~ 60 days

Madden & Julian [1971; 1972], Lau and Waliser [2005], Zhang [2005]

Madden-Julian oscillation

Retrieved from 690 – 725 cm-1

2.5°×2° gridded Level 3 Cloud-cleared Nov 2002 – Feb 2010 Sensitivity peak at 5 – 10 km Accurate to 1 – 2 ppmv

AIRS CO2

Chahine et al. [2008]

(1) Intraseasonal anomalies of daily data were obtained by a. Including boreal winter data onlyb. Removing the climatological seasonal cyclec. Bandpass filtering (30–90 days)

(2) MJO phase determined by a pair of Real-time Multivariate MJO indices (RMM1 & RMM2, 1974–present) [Wheeler & Hendon, 2004] http://www.cawcr.gov.au/bmrc/clfor/cfstaff/matw/maproom/RMM/

(3) Composite MJO cycle calculated by averaging bandpassed daily anomalies for each phase

Methodology

Defined as two leading extended EOFs of 36-year OLR data RMM1 − enhanced convection over the Maritime Continent RMM2 − enhanced convection over the Pacific Ocean (RMM1,RMM2) characterizes the eastward propagation Use only strong MJO events (RMM1

2 + RMM22 ≥ 1)

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RMM Index

Li et al., PNAS, 2010

Modulated CO2

Enhanced CO2 over convective regions

Small Bias due to H2O Absorption

MJO of H2O at 600 hPa ≈ 1.4 g/kg [Tian et al., 2006] Potential Bias in CO2 ≈ 1.4 0.13 < 0.2 ppmv

Observations between 10°S – 10°N

Li et al., PNAS, 2010

Li et al., PNAS, 2010

Vertical Gradient Verification of vertical gradient using

in situ measurements

First observation of intraseasonal variability in CO2

Lower-tropospheric vertical motions drive the MJO of mid-tropospheric CO2

Vertical gradients in CO2

Statistically robust > 20 MJO events and 9 millions of AIRS retrievals being used Negligible effects due to H2O

Average MJO amplitude ~1.5 ppmv = 0.5% Critical for determining surface CO2 sources and sinks [Rayner

& O’Brien, 2001]

Not seen in ECMWF’s GMES-MACC assimilated CO2 [provided by Dr. Bechtold] Relationship between tropical dynamics and CO2 not well unde

rstood

Summary

Li et al. AGU Fall 2010 A54D-01

Thank you!