Comparison of Upper Ocean and Lower Atmosphere Temperatures over the Western North Pacific in Summer

Abstract

A strong meridional gradient of temperature highlights the upper ocean characteristics of the western North Pacific. The Kuroshio Extension (KE) and subarctic frontal zone (SAFZ) contribute to the distinct thermal variations at different depths of the upper ocean; the KE-associated variations is observed in the main thermocline (about 200–600 m), while those related to the SAFZ is found in the mixed layer. Accordingly, the KE exhibits a distinct meridional gradient of sea surface height (SSH) and a modest sea surface temperature (SST) gradient, whereas the SAFZ shows a strong meridional gradient in SST, not in SSH. The upper-ocean temperature in the western North Pacific is analyzed focusing on the summer season and compared with that of lower atmosphere by using both reanalysis dataset and in situ observation data obtained in the summer of 2018, which includes CTD, underway CTD, XCTD, and radiosonde. This study examines the vertical temperature profiles of upper ocean and atmospheric boundary layer, and discusses cross-frontal differences in the lower atmospheric structure possibly associated with the strong meridional gradient of the upper ocean characteristics in the western North Pacific.