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Model experiments. CAM4.0 was run for 10 years without any forcing at 1deg resolution - the control run (data ocean ). Each of the forced experiments were run for 135 days.

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Model experiments

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Model experiments

Model experiments

  • CAM4.0 was run for 10 years without any forcing at 1deg resolution - the control run (data ocean).

  • Each of the forced experiments were run for 135 days.

  • 18 forced experiments with eastward moving heating and cooling signals were run - each for 10 different initial conditions :

  • the 31 May of each year from the control run - 10 JJAS I.C.

  • the 30 Nov of each year from the control run - 10 DJFM I.C.

  • 2 forced experiments with northward moving forcing were run - each for 10 different initial conditions, 1 for each season’s I.C.

  • 2 forced experiments with stationary forcing over the equatorial Indian Ocean were run - each for 10 different initial conditions, 1 for each season’s I.C.

  • 6 forced experiments each with varying latitudinal extent of observed Diabatic Heating were run - each for 10 different initial conditions, 3 for each season’s I.C.


Model experiments

  • The forced experiments with idealized signals have heating and cooling cells based on idealized MJO-like oscillations:

  • ellipses with Gaussian distribution (cell size 60deg lon, 10deg lat)

  • with middle heavy and bottom heavy vertical profiles

  • alternate heating and cooling signals

  • maxima is 1.5K/day for both the profiles reducing to almost zero at the top and bottom of the atmosphere

  • They cover the equatorial Indo-Pacific region

Vertical Profile:

bottom heavy,

middle heavy,


Model experiments

Forced Signals (Idealized)

Multichannel singular spectrum (MSSA) has been used to identify the temporal variability and to determine the coherent intraseasonal space-time patterns for different variables.

The 45 day period oscillation is studied, which also captures the MJO.


Model experiments

JJAS: Precipitation (mm/day)

Observation Control_runf_rs3(45dp)


Model experiments

DJFM: Precipitation (mm/day)

Observation Control_run f_rw3(45dp)


Model experiments

  • The JJAS season is better captured than the DJFM season by CAM4.0 as seen in the control run.

  • The best results are seen for the 45 day period (dp) oscillation with middle heavy vertical profile, for both the JJAS and DJFM seasons.

  • For JJAS, the 45dp forcing signal improves the anomaly band tilts.

  • For DJFM, the 45dp forcing signal improves the eastward propagation of the anomalies and reduces the northern hemispheric anomalies.

  • It is interesting to note that an eastward propagating forcing improves the latitudinal structure of the anomalies.


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