Seasonal Dependence of the Madden-Julian Oscillation (MJO) El Niño-Southern Oscillation (ENSO) Relationship 1. Hendon et al

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1 Seasonal Dependence of the Madden-Julian Oscillation (MJO) El Niño-Southern Oscillation (ENSO) Relationship 1 Hendon et al Marcela Ulate M 1 Hendon, H.H., M.C. Wheeler, and C. Zhang, 2007: Seasonal Dependence of the MJO ENSO Relationship. J. Climate, 20,

2 Outline MJO ENSO Equatorial Cold Tongue (coastal upwelling). Western Pacific warm pool. Is there a relationship between MJO and ENSO? If there is, why is it important? What is the seasonality of this relationship? What is the Mechanism proposed in the paper to explain it? Conclusions

3 MJO Intraseasonal oscillation (40-50 days period) in the tropics. Madden and Julian 1971: Used 10 years of data of daily rawinsonde over Canton Island. They found a maximum in the frequency range corresponding to periods of days for surface pressure, winds at 850hPa and 150hPa, and temperature. 150 U (m/s) 850 U (m/s) P (hpa)

4 OLR (W/m2) U (m/s) Contours 0.5 m/s ---<0 Shaded ±0.5m/s

5 Seasonality of MJO U850 (m/s) Pcp (mm/day) 850 moisture convergence (g/kgm)

6 ENSO Oscillation in the sea surface temperature (SST), atmospheric winds and convection in the Equatorial Pacific Ocean. Warm Phase of ENSO (El Niño): Positive anomalies of SST. Cold Phase of ENSO (La Niña): Negative anomalies of SST.

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8 Monthly Averaged SST ( C) U (m/s) El Niño SST El Niño anomalies Pink Line: Annual Cycle

9 Is there a relationship? Relationship between MJO and ENSO Relationship between the Western Pacific activity of MJO and ENSO. Stronger that the Global MJO activity. Why is important? The basic Relationship: MJO El Niño (Warm Phase of ENSO). MJO Activity => Eastward propagation of westerly wind anomalies. Development of Downwelling Kelvin wave=> Warm the eastern Pacific.

10 MJO Activity=> Downwelling Kelvin Wave => Downwelling of the thermocline (+ Feedback to El Niño conditions).

11 MJO El Niño Intense MJO activity before El Niño. (Weickmann 1991, Kessler et al. 1995, McPhaden 1999, Zhang and Gottschalck 2002, Lau 2005). MJO forced Kelvin waves in the western equatorial Pacific. Strength of El Niño, after 6-12 months of intense activity of the MJO in the west pacific. (Zhang and Gottschalck 2002) Eastern Pacific: Warming Western Pacific: Shift of the Western Pacific Warm pool to the east.

12 What is the Seasonal Dependence of the MJO ENSO Relationship? El Niño MJO activity in the Western Pacific during Spring- Early Summer (NH) leads to a strength of El Niño in the following Autumn-Winter (NH).

13 Amplitude of MJO Zonal surface wind (Usfc) or Outgoing Longwave Radiation (OLR) for the Pacific, averaged over 5 S-5 N. Period MJO Signal: MJO-filter: Eastward wave numbers (1-5) Periods of days. Amplitude: MJO Usfc = σ 2 Usfc MJO OLR = σ 2 OLR To compared with El Niño activity, they used El Niño 3-4 SST Series.

14 Near Equatorial Component of MJO Zonal Wind anomalies (5N 5S)

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16 Lagged relation of MJO activity with ENSO

17 Lagged relation of Western Pacific MJO activity with ENSO

18 Lagged relation of Western Pacific MJO activity with ENSO

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20 Hypothesis for mechanism of interaction

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23 Relationship between MJO and ENSO (Conflicting results) Arguments that the eastward shift of the MJO is just a response of the change of SSTs, at the early stages of El Niño. Is MJO affecting ENSO or is ENSO affecting MJO? Intraseasonal anomalies of wind and convection over the Western Pacific of different time and spatial scales, also lead to El Niño. (Luther et al. 1993, Gutzler 1991, Vecchi and Harrison 2000). Stochastic Forcing => ENSO

24 Conclusions The relationship between ENSO and MJO is clear with the plots in the paper. The authors proposed a mechanism. BUT the question of the interaction between them is still open. The authors let open the possibility that the lagged relationship could be nothing more than the proper evolution of atmosphere through El Niño cycle. Limitations of the data.(ncep /NCAR Reanalysis vs Observations) A lot of the papers in this subject have a strong statistical component. We need to know more about the mechanisms. Is it really MJO the one that affects ENSO or is it ENSO the one that is affecting MJO? Is the relationship for la Niña linear? ( Should we expect the opposite than El Niño?)

25 References Kessler, W.S., 2001: EOF Representations of the Madden Julian Oscillation and Its Connection with ENSO. J. Climate, 14, Kessler, W.S., 2001: EOF Representations of the Madden Julian Oscillation and Its Connection with ENSO. J. Climate, 14, Kessler, W.S., and R. Kleeman, 2000: Rectification of the Madden Julian Oscillation into the ENSO Cycle. J. Climate, 13, Kiladis, G.N., K.H. Straub, and P.T. Haertel, 2005: Zonal and Vertical Structure of the Madden Julian Oscillation. J. Atmos. Sci., 62, Madden, R.A., and P.R. Julian, 1972: Description of Global-Scale Circulation Cells in the Tropics with a Day Period. J. Atmos. Sci., 29, Madden, R. A, and P.R. Julian, 1971: Detection of a Day Oscillation in the Zonal Wind in the Tropical Pacific.. J. Atmos. Sci., 28, McPhaden, M. J., 1999: Genesis and evolution of the El Niño. Science, 283, Vecchi, G.A., and D.E. Harrison, 2000: Tropical Pacific Sea Surface Temperature Anomalies, El Niño, and Equatorial Westerly Wind Events. J. Climate, 13, Zhang, C., and J. Gottschalck, 2002: SST Anomalies of ENSO and the Madden Julian Oscillation in the Equatorial Pacific. J. Climate, 15,

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