Opposite responses of the diurnal amplitude of sea surface temperature to the Madden-Julian Oscillation

Both observations and empirical model results show that the responses of the diurnal amplitude of sea surface temperature (DSST) to the Madden-Julian Oscillation (MJO) in the tropical regions are opposite on the two sides of a pivot longitude, which varies seasonally. This pivot longitude occurs at 180° in boreal winter, but moves to 150°E in boreal summer. When the active convection center of the MJO is located to the west of the pivot longitude, reduced solar insolation and enhanced wind speed decrease DSST; when the active convection center moves to the east of the pivot longitude, reduced wind speed increases DSST. Due to the opposing wind speed anomalies across the pivot longitude, opposite responses to the MJO can be seen in latent heat flux anomalies, evaporation rate anomalies and surface roughness anomalies. These findings suggest that opposite responses in the tropical regions on the west and east of the pivot longitude to the MJO be common for variables that are closely related to wind speed.