Interdecadal Variations of the March Atmospheric Heat Source over the Southeast Asian Low-Latitude Highlands

Based on the fifth-generation reanalysis dataset from the European Centre for Medium-Range Weather Forecasts for 1979–2019, we investigated the effects of the circumglobal teleconnection (CGT) on the interdecadal variation of the March atmospheric heat source (AHS) over the Southeast Asian low-latitude highlands (SEALLH). The dominant mode of the March AHS over the SEALLH features a monopole structure with an 8–11-year period. Decadal variations in the AHS make an important contribution to the 11-year low-pass filtered component of the AHS index, whichexplains 54.3% of the total variance. The CGT shows a clear interdecadal variation, which explains 59.3% of the total variance. The March AHS over the SEALLH is significantly related to the CGT on interdecadal timescales. When the CGT is optimally excited by a significant cyclonic vorticity source near northern Africa (i.e., in its positive phase), the SEALLH is dominated by anomalous southerly winds and ascending motions on the east of the anomalous cyclone. The enhanced advection and upward transfer result in a high-enthalpy air mass that converges into and condenses over the SEALLH, leading to a larger-than-average March AHS over this region. The key physical processes revealed by this diagnostic analysis are supported by numerical experiments.