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Yan Xue, Wayne Higgins and Vernon Kousky Climate Prediction Center, NCEP/NWS

Influences of the Madden Julian Oscillation on Temperature and Precipitation in North America During Weak/Neutral ENSO NH Winters. Yan Xue, Wayne Higgins and Vernon Kousky Climate Prediction Center, NCEP/NWS

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Yan Xue, Wayne Higgins and Vernon Kousky Climate Prediction Center, NCEP/NWS

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  1. Influences of the Madden Julian Oscillation on Temperature and Precipitation in North AmericaDuring Weak/Neutral ENSO NH Winters Yan Xue, Wayne Higgins and Vernon Kousky Climate Prediction Center, NCEP/NWS for the 27th Annual Climate Diagnostics and Prediction Workshop held in Fairfax, Virginia on October 21-25, 2002

  2. Review • The MJO has a strong influence on the atmospheric circulation in the tropics and subtropics Madden and Julian 1971; Weichmann et al. 1985; Lau and Chan 1985; Knutson and Weickmann 1987; Kiladis and Weickmann 1992; Kayano and Kousky 1999 • The MJO has some influence on the midlatitudes ( e.g. precipitation events along the west coast of U.S.) Mo and Higgins 1998; Higgins et al. 2000

  3. Approach • Ten MJO indices are used to describe the eastward propagation of the MJO • Real time monitoring • Composite • Extreme event frequency anomaly • Composites are keyed to the convectively active phase of each MJO index • Atmospheric circulation • Temperature • Precipitation • Extreme heavy precipitation (>75th percentile), extreme warm (>90th percentile) and cold (<10th percentile) surface air temperature

  4. Data • Pentad data from NCEP/NCAR reanalysis • 200-hPa CHI, PSI, u, v. • 500-hPa Z • 2.5o latitude/longitude, 1958 – present • Pentad Outgoing Longwave Radiation • 2.5o latitude/longitude, 1979 – present • Pentad global surface air temperature (personal communication with Ping-Ping Xie) • 2.5o latitude/longitude, 1978 – present • GPCP global pentad precipitation analysis • 2.5o latitude/longitude, 1979 – present

  5. MJO Indices • Band-passed (25-87 day) pentad 200-hPa velocity potential (CHI) • Extended empirical orthogonal function (EEOF) analysis of the filtered CHI • Extended winter (November – April) • ENSO-neutral and weak ENSO winters (1979-2000) • 30oS – 30oN, Ten time-lagged patterns • Projection of the filtered CHI onto the ten patterns of the first EEOF

  6. INDEX 1 (80OE) INDEX 6 (120OW) INDEX 2 (100OE) INDEX 7 (40OW) INDEX 8 (10OW) INDEX 3 (120OE) INDEX 9 (20OE) INDEX 4 (140OE) INDEX 5 (160OE) INDEX 10 (70OE)

  7. Depth 20OC Anom December 2001 June 2001

  8. Composite Methodology • MJO Index > 0.8 sigma (standard deviation) • Using multiple pentads around the peaks (3-4 pentads for strong MJOs / 1-2 pentads for weak MJOs) • Composite is done with unfiltered data but the climatological mean for 1979-1995 was first removed and then the winter season (Dec-Apr) mean are removed. • Two-tailed student’s t test (95% significance)

  9. Composite Members • Index 1: 80 pentads (29 MJO cases) • Index 2: 72 pentads (27 MJO cases) • Index 3: 71 pentads (25 MJO cases) • Index 4: 70 pentads (26 MJO cases) • Index 5: 75 pentads (26 MJO cases) • Index 6: 78 pentads (28 MJO cases) • Index 7: 79 pentads (27 MJO cases) • Index 8: 75 pentads (27 MJO cases) • Index 9: 67 pentads (25 MJO cases) • Index 10: 83 pentads (29 MJO cases)

  10. Seasonality of MJO

  11. 20 W/m2 OLR cint = 4 w/m2

  12. 200-hPa Zonal Wind cint = 2 m/s

  13. Precipitation cint = 0.2 mm/day Shading is percentage departure relative to the climatology

  14. 60 m 500-hPa Height cint = 10 m

  15. Surface Air Temperature cint = 0.5OC +1OC -1OC

  16. Extreme Frequency Anomaly • Base pentads are composed of all the pentads in the neutral/weak ENSO winters (Dec-Apr) with the MJO pentads excluded. • For each MJO index, compute the percentage of the MJO pentads with pentad amounts greater than the base pentads’ x percentile (Pmjo). • For each MJO index, compute the frequency anomaly in percent of expected number of extreme events: Panom = (Pmin/(1- x) – 1) Gershunov and Barnett 1998, J. Climate Percent for mjo pentads percent for base pentads

  17. Extreme Warm (> base 90th percentile) Surface Air Temperature Frequency Anomaly (cint=20%) +80% -80% Base 90th percentile distribution

  18. Extreme Cold (< base 10th percentile) Surface Air Temperature Frequency Anomaly (cint=20%) Base 10th percentile distribution

  19. Extreme Heavy (> base 75th percentile) Precipitation Frequency Anomaly (cint=20%) Base 75th percentile distribution

  20. Summary • Ten MJO indices were calculated as projections of pentad 200-hPa velocity potential onto ten time-lagged patterns of the first EEOF. • Keying on the convectively active phases of the ten MJO indices, ten composites of the MJO events during ENSO-neutral and weak ENSO winters were constructed for various fields. • Significant MJO-related influences on both means and extreme events of surface air temperature and precipitation in the North America are found.

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