Ocean interactions are known to be important in understanding and modeling tropical intraseasonal variability. We explore the role of major oceanic processes like ENSO (El-Nino Southern Oscillations) and IOD (Indian Ocean Dipole) on intraseasonal oscillations like Madden-Julian Oscillation (MJO) as well as convectively coupled equatorial waves (Kelvin, Rossby (ER), Mixed-Rossby gravity and Tropical Depressions together MT). Using space time filtering of daily interpolated outgoing longwave radiation to quantify waves, spatio-temporal variations in correlations with SST are studied. Both OLR and SST data are taken from daily optimal interpolated data of the National Oceanic and Atmospheric Administration (NOAA) for a period 1982 to 2013.
Spatial distribution of correlations between annual mean wave intensity and SST show high heterogeneity showing that wave intensity doesn’t directly correspond with SST. Further, correlations are carried out for different seasons like DJF (December, January and February), MAM (March, April and May), JJA (June, July and August) and SON (September, October and November). The result shows that these relations largely vary dependent on the season as well as location for each of the waves. The correlations show patterns like El-Nino and La-Nina over Pacific. Correlations with Nino 3 index confirm the relationship between El-Nino and these waves. While Kelvin and Rossby waves intensify during El-Nino, MT waves are shown to intensify during La-Nina. Zonal and meridional distribution of moist static energy (MSE) during different phases of El-Nino is shown to be major factor in the observed changes in the intensity of waves along with associated vertical shear. Also, some dipole kind of correlations structure is found over Indian Ocean for certain waves. The statistical relation between waves and Dipole Moment Index (DMI) show significant negative correlations with MJO and ER and positive correlations with MT.