Model experimentsCAM4.0 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.

Vertical Profile:

middle heavy,

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

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.

JJAS: Precipitation (mm/day) Observation Control_run f_rs3(45dp)

DJFM: Precipitation (mm/day) Observation Control_run f_rw3(45dp)

• 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.