Satellite data reveal the 3-D moisture structure of Tropical Intraseasonal Oscillation and its coupling with underlying ocean

The water-vapor profiles obtained from the Atmospheric Infrared Sounder (AIRS) on Satellite Aqua are used to document the 3-D moisture structure of the boreal-summer Tropical Intraseasonal Oscillation (TISO) over the Indo-western Pacific region. With the support of several other Satellite data sets, the interactions between the TISO and underlying ocean are also investigated. The AIRS data reveal much larger tropospheric moisture perturbations than those depicted in previous reanalysis and analysis data sets. It also reveals a drying Atmospheric Boundary Layer (ABL) below the TISO convection probably due to the associated downdrafts. Before the occurrence of TISO convection, both positive Sea Surface Temperature (SST) anomaly and ABL moistening are observed. Further analysis suggests that the positive SST anomaly is the major contributor to the ABL moistening through enhancing surface evaporation. Therefore, the intraseasonal SST anomaly could positively feed back to the atmosphere through moistening the boundary layer, destabilizing the troposphere, and contributing to the northeastward propagation of the TISO.