The spatiotemporal characteristics and generation mechanism of submesoscale processes (SMPs) in the low-latitude western Pacific Ocean are investigated based on 1/30º Ocean General Circulation Model for Earth Simulator (OFES) outputs and mooring measurements. Elevated submesoscale activities are detected east of the Mindanao Island and north of Halmahera Island along the paths of Mindanao Current and Halmahera Eddy. Their spatial and temporal scales are shorter than 80 km and 20 days, respectively. Mooring observations reveal that the SMPs not only exit in the mixed layer, but also penetrate the thermocline to 150m. SMPs exhibit significant seasonal cycle, with high submesoscale kinetic energy (SKE) values in summer and autumn and relatively weak SKE values in winter and spring. Due to the shallow mixed layer depth, the pathway that SMPs extract available potential energy through mixed layer baroclinic instability is blocked. The barotropic instability processes associated the current-islands interactions are responsible for the generation and seasonal modulation of SMPs. Further energetic diagnostic analysis indicates that in the barotropic energy transfer chain, the mean kinetic energy is the main energy source for SKE, and 65.6% kinetic energy that SMPs obtain is from the mean flow field, and that of only 35.4% is from mesoscale eddy field. Furthermore, the SKE budget results imply a forward dissipation process to turbulence, which emphasizes the effects of SMPs on the diapycnal mixing in the low-latitude western tropical Pacific Ocean.

submesoscale processes,barotropic instability,seasonal variation,low-latitude western Pacific Ocean,mesoscale eddy