Tropical Mid-Tropospheric CO 2 Variability driven by the Madden-Julian Oscillation King-Fai Li 1, Baijun Tian 2, Duane E. Waliser 2, Yuk L. Yung 1 1 California Institute of Technology, Pasadena 2 Jet Propulsion Laboratory, Pasadena Special Thanks to Dr. Peter Bechtold (ECMWF) Li et al. (2010), PNAS 107, 19171

Motivation Chahine et al. [2008]  AIRS CO 2 (~5 km) reveals influences from circulations  Surface sources appearing in mid-troposphere Convection and stratosphere-troposphere exchange Jet-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- propagating 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 CO 2 Chahine et al. [2008]

(1)Intraseasonal anomalies of daily data were obtained by a. Including boreal winter data only b. Removing the climatological seasonal cycle c. Bandpass filtering (30–90 days) (2)MJO phase determined by a pair of Real-time Multivariate MJO indices (RMM 1 & RMM 2, 1974–present) [Wheeler & Hendon, 2004] (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  RMM 1 − enhanced convection over the Maritime Continent  RMM 2 − enhanced convection over the Pacific Ocean  (RMM 1,RMM 2 ) characterizes the eastward propagation  Use only strong MJO events (RMM RMM 2 2 ≥ 1) × × × × × × ×× × × ×× × ×× × RMM Index

Li et al., PNAS, 2010 Modulated CO 2  Enhanced CO 2 over convective regions

Small Bias due to H 2 O Absorption  MJO of H 2 O at 600 hPa ≈ 1.4 g/kg [Tian et al., 2006]  Potential Bias in CO 2 ≈ 1.4  0.13 < 0.2 ppmv Observations between 10°S – 10 ° N Li et al., PNAS, 2010

Vertical Gradient  Verification of vertical gradient using in situ measurements

 First observation of intraseasonal variability in CO 2  Lower-tropospheric vertical motions drive the MJO of mid- tropospheric CO 2  Vertical gradients in CO 2  Statistically robust  > 20 MJO events and 9 millions of AIRS retrievals being used  Negligible effects due to H 2 O  Average MJO amplitude ~1.5 ppmv = 0.5%  Critical for determining surface CO 2 sources and sinks [Rayner & O’Brien, 2001]  Not seen in ECMWF’s GMES-MACC assimilated CO 2 [provided by Dr. Bechtold]  Relationship between tropical dynamics and CO 2 not well understood Summary

Li et al.AGU Fall 2010A54D-01 Thank you!