The Influence of the Madden–Julian Oscillation on Ocean Surface Heat Fluxes and Sea Surface Temperature

The Madden–Julian oscillation (MJO) involves pronounced variations in convection and large-scale circulation throughout the tropical troposphere. In addition, the MJO is also related to dynamic and thermodynamic variability near the surface and the upper ocean. This study uses observational data to characterize the changes in surface heat fluxes and sea surface temperature (SST) during the life cycle of the MJO. Variations in convective activity are described with outgoing longwave radiation (OLR) during the period January 1985 through September 1994. International Satellite Cloud Climatology Project data (January 1985– April 1991) and European Centre for Medium-Range Weather Forecasts surface analyses (January 1985–December 1994) are used to derive surface fluxes of net shortwave radiation (SW), latent heat (E ), their difference (Q 5 SW 2 E ), and SST. The spatial patterns of OLR, SW, E, Q, and SST anomalies reveal that the region of positive OLR anomalies that precede the occurrence of enhanced convection is associated with positive SW and negative E anomalies, which result in positive Q anomalies. The prevailing conditions in the region of positive Q anomalies favor the development of positive SST anomalies, which lead to variations of enhanced convection. In contrast the region of negative OLR anomalies is associated with negative SW and positive E anomalies. These conditions induce negative Q anomalies, which favor the formation of negative SST anomalies. The above results suggest a possible feedback between the oscillation and intraseasonal variations in SST and this may be an important mechanism for numerical simulations of the life cycle of the MJO. FIG. 1. Ensemble spectrum of SST over a reference site in the Indian Ocean (2.58S, 808E). Period: 1985–94. Smoothed solid line represents the background red-noise spectrum and dashed line is the 95% significance level. The band (25–90) days is indicated in the upper-left corner, and BW denotes the spectrum bandwidth.