Influence of Tropical Biennial Oscillation on Carbon Dioxide Jingqian Wang 1, Xun Jiang 1, Moustafa T. Chahine 2, Edward T. Olsen 2, Luke L. Chen 2, Maochang Liang 3, and Yuk L. Yung 4 1 Department of Earth and Atmospheric Sciences, University of Houston, TX 77204, USA. 2 Science Division, Jet Propulsion Laboratory, California Institute of Technology, 3 Research Center for Environmental Changes, Academia Sinica, Taipei, Taiwan. 4 Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, USA. Abstract Indonesia is the world’s third largest emitter of the greenhouse gas, CO 2. In addition to the source contribution by anthropogenic emissions, agricultural and forest fires, changes in atmospheric circulation also influence the CO 2 concentration over Indonesia. We used the mid-tropospheric CO 2 retrievals from the Atmospheric Infrared Sounder (AIRS) to investigate variability of CO 2 over Indonesia. We found a signal of periodicity two years in the power spectrum of the mid-tropospheric CO 2 over Indonesia, which might be related to the Tropical Biennial Oscillation (TBO). During a strong monsoon year, the Western Walker Cell is strong, resulting in enhanced CO 2 transportation from the surface to the mid-troposphere due to the strong upwelling. As a result, there are positive (negative) CO 2 anomalies at mid-troposphere (surface). During a weak monsoon year, the Western Walker Cell is weak. Less CO 2 will be transported to the mid-troposphere for the weak monsoon year. Indian monsoon index is anti-correlated with the surface CO 2 observation and positive correlated with the mid- tropospheric CO 2 at Indonesia. MOZART-2 model is also used to investigate the influence of TBO on mid-tropospheric CO 2. The model results are consistent with the observations.  Tropospheric Biennial Oscillation (TBO): Defined as the tendency for a relatively strong monsoon to be followed by a relatively weak one, and vice versa.  A relatively strong monsoon can be defined as P i-1 P i+1  A relatively weak monsoon can be defined as P i-1 > P i <P i+1  Strong monsoon has strong Western Walker Cell  Weak monsoon has weak Western Walker Cell  Figure. 1 Circulation of TBO : Data and Model Table 1: Variances, spectral peaks, and correlations (Lag = 0) for the first modes of the sea surface temperature, tropopause pressure, and column ozone. The numbers in parentheses denote significance levels. Observation Results Power Spectrum of AIRS CO 2 at Indonesia Time Series of CO 2 & GPCP Precipitation Mean Value of AIRS CO 2 Conclusions  The AIRS CO 2 has a signal of about 2 years at Indonesia.  The Surface CO 2 is inversely proportional to the Indian Monsoon Index.  Strong monsoon years have more CO 2 in the mid-troposphere at Indonesia due to the strong Western Walker Cell.  Weak monsoon years have less CO 2 in the mid-troposphere at Indonesia due to the weak Western Walker Cell.  The MOZART-2 Model CO 2 results at Indonesia are consistent with the observation. Mean Value of Model CO 2  Figure 2. The power spectrum of AIRS CO 2 at Indonesia (5  S ~ 20  N, 100  E ~ 150  E). Dotted line is the red-noise spectrum, Dash-dot line and dashed line are 10% and 5% significance levels. Introduction  Figure 3. AIRS CO 2 concentration (black solid line, averaged from Jun to Sep at 5  S~20  N, 100  E~150  E) and Indian JJAS Monsoon index calculated from GPCP precipitation (red dash line).  Figure 4. The time series of CO 2 surface observation at Bukit Kototabang, Indonesia (0.2  S,  E) and Indian JJAS Monsoon Index (red dash line). References Chahine, M., C. Barnet, E. T. Olsen, L. Chen, and E. Maddy, 2005: On the determination of atmospheric minor gases by the method of vanishing partial derivatives with application to CO2. Geophys. Res. Lett., 32, doi: /2005GL Chahine, M., et al., 2008: Satellite remote sounding of mid-tropospheric CO2. Geophys. Res. Lett., 35, doi: /2008GL Chang C. P. and Li T., 2000: A Theory for the Tropical Tropospheric Biennial Oscillation. J. Atmos. Sci., 57(14), Jiang, X., M. T. Chahine, E. T. Olsen, L. Chen, and Y. L. Yung, 2010: Interannual Variability of Mid-tropospheric CO2 from Atmospheric Infrared Sounder. Geophys. Res. Lett. 2010GL Meehl, G. A., and Arblaster J. M., 2002: The Tropospheric Biennial Oscillation and Asian–Australian Monsoon Rainfall. J. Climate, 15,  Figure 5. (a) Mean value of AIRS mid- tropospheric CO 2 concentration averaged over JJAS in strong monsoon years (2003, 2005 and 2007) (b) Mean value of AIRS mid- tropospheric CO 2 concentration averaged over JJAS in weak monsoon years (2004, 2006 and 2008) (c) Difference between the strong and weak monsoon years.  Data: I: Global Precipitation Climatology Project (GPCP V 2.1) II: GLOBALVIEW-CO 2, ESRL network surface flask measurements III: Satellite CO 2 retrieval from AIRS  Model: Model of Ozone and Related Chemical Tracers version 2 (MOZART-2) I: Driven by ECMWF-Interim data. II: The horizontal resolution is 2.8° (latitude)  2.8° (longitude). III: 45 vertical levels (surface to 50 km)  Figure 7. (a) Mean value of mid-tropospheric CO 2 concentration from MOZART-2 model in strong monsoon years (JJAS of 1996 and 2007) (b) Mean value of mid-tropospheric CO 2 concentration from MOZART-2 model in weak monsoon years (JJAS of 1999 and 2002) (c) The difference between strong and weak monsoon years (Meehl and Arblaster, 2002) The Model result of CO 2 in the mid- troposphere correlate well with Indian Monsoon index. Correlation Coefficient is  Figure 6. Time series of MOZART-2 model mid- tropospheric CO 2 concentration (Black solid line) and TBO (dots) from 1991 to  Model mid-tropospheric CO 2 concentration is the mean value of the area 5  S~20  N, 100  E~150  E in JJAS.  TBO is defined by Meahl and Arblaster (2002)  Red dots are strong monsoon  Blue dots are weak monsoon (a) (b) (c) (b) (c) (a) A51C There is a signal about 2 years within 5% significant level. The AIRS mid-tropospheric CO 2 is positive correlated with Indian JJAS Monsoon index, with a correlation coefficient of The surface CO 2 is inversely proportional to the Indian JJAS Monsoon index with a correlation coefficient of Model Results Time series of Model CO 2 & TBO