3. A research case study: The MaddenJulian Oscillation

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3. A research case study The Madden-Julian
Oscillation

• Original colour diagrams
• Animations
• Please use in conjunction with the lecture notes

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3.1 Introduction
Outgoing Longwave Radiation (OLR)Northern winter
mean (DJF 1979/80-1994/95)
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Animation of MJO life cycle CMAP precipitation
rate totals and anomalies (mm day-1)
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3.2.1 Reanalysis data
1000-hPa geopotential height field on 1 January
2001. Units are m.
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Daily maps of 500 and 925-hPa geopotential height
during December 2000. Units are m.
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3.2.2 Outgoing longwave radiation (OLR)
Global OLR map for 1 January 2001. Units are W
m-2.
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3.2.3 Global precipitation data
Global map of CMAP precipitation rate for pentad
centred on 1 January 2001. Units are mm day-1.
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3.2.4 Sea surface temperature (SST)
Global SST map for week centred on 1 January 2001
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3.3.1 Annual cycle

• Daily time series of 200-hPa u wind at 80oE, 0oN.
  
• 1 Jan 1996 1 Jan 1998. Annual cycle in bold.
  (b) Anomalies

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3.3.2 Filtering
Filter response for a 120-weight 20-200-day
Lanczos filter.
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Daily time series of 200-hPa u wind at 80oE,
0oN.1 Jan 1996 1 Jan 1998. Anomalies (black).
20200-day filtered (red). 30-70-day filtered
(blue).
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Time series of a single sine wave of period 48
days (solid line), the time series passed through
a 20-200-day band-pass Lanczos filter (dotted
line), and a 30-70-day filter (dashed line), both
with 241 weights. From Matthews (2000)
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3.3.4 MJO life cycle
Animation of OLR anomaly maps, formed by
regression onto first two EOFs of 20-200-day
filtered OLR. Contour interval is 5 W m-2.
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Animation of SLP anomaly maps, formed by
regression onto first two EOFs of 20-200-day
filtered OLR. Contour interval is 10 Pa.
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3.4.6 Equatorial waves
Animation of transient response (Matsuno-Gill
model) to an equatorial heat source in the
equatorial Pacific switched on at t0.
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As before, but with heating switched off at t5
days, to show propagation of free equatorial
Kelvin and Rossby waves
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3.5.1 Atmospheric response to MJO heating
anomalies
Equatorial Kelvin-Rossby wave response to
negative heating anomaly
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Equatorial Kelvin-Rossby wave response to fixed
dipole in heating
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Animation of SLP anomaly maps, formed by
regression onto first two EOFs of 20-200-day
filtered OLR. Contour interval is 10 Pa.
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3.5.2 Ocean component of MJO
Colour shading SST anomaly Contours OLR
anomaly solid pos. (wet), dashed neg. (dry)
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Conceptual coupled ocean-atmosphere model of MJO

• Mean state surface westerlies over Indian Ocean,
  easterlies over western Pacific
• Warm SST anomaly has developed over Indian Ocean
  (start of MJO)
• Atmospheric response deep convection, rainfall
  and latent heating
• Shortwave (solar radiation) is reflected back to
  space by clouds reduction in downward QSW
• Western Indian Ocean surface westerly anomalies
  from equatorial Rossby wave response to latent
  heating add to mean surface westerlies wind
  speed increases upward latent heat flux QL
  increases
• Indonesia surface easterly anomalies from
  equatorial Kelvin wave response to latent heat
  partially cancel mean surface easterlies wind
  speed decreases upward latent heat flux QL
  decreases
• Net surface energy flux anomalies cooling of
  ocean in Indian Ocean, warming of ocean in
  Indonesia
• Original warm SST anomaly moves eastward
• Clouds, rainfall and the rest of the MJO follow

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Warm SST
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3.6.2 Ocean forcing atmosphere
Equatorial OLR (shaded) and SST (contoured)
anomalies. See handout for details.