Enhancement of lower tropospheric winter synoptic temperature variations in Southwest China and the northern Indochina Peninsula after 2010

Abstract

In this study, long-term change in winter synoptic temperature variations in Southwest China and the northern Indochina Peninsula from 1979 to 2017 (39 years) is documented. A sharp increase in synoptic temperature variation is found after 2010, indicating stronger day-to-day temperature change in the last decade. The increasing variation is attributed to stronger horizontal wind on a synoptic timescale after 2010. On the other hand, transient eddies show stronger intensity after 2010 when approaching Southwest China and the northern Indochina Peninsula (SWCNIP), contributing to the stronger synoptic horizontal wind. According to the eddy kinetic energy budget, the stronger horizontal wind is due primarily to the larger baroclinic energy conversion from eddy potential energy to eddy kinetic energy after 2010. Furthermore, a larger potential energy conversion from the mean flow to transient eddies is observed in SWCNIP after 2010. This plays an important role in sustaining the intensity of transient eddies. It is also noted that the intensification of transient eddies after 2010 is caused by warming in the western tropical Pacific and the Bay of Bengal and strengthened synoptic eddies along the southern part of the Tibetan Plateau.