Interannual variability of winter surface air temperature in central-eastern Tibetan Plateau: the role of atmospheric wave train over northern subtropics and Indian Ocean subtropical dipole mode
摘要
The winter surface air temperature (SAT) over the central-eastern Tibetan Plateau (TP) exhibits a significant relationship with global weather and climate, but its interannual variability has received less attention. This study examines the interannual variation of winter SAT over the TP and its potential drivers. The winter SAT over the TP varies largely in phase, with a larger amplitude in the northern region. Positive winter SAT anomalies over the TP are closely linked to a local anomalous anticyclone with a quasi-barotropic vertical structure. This local anomalous anticyclone contributes to anomalous warming SAT over the TP via enhanced meridional temperature advection by southerly wind anomalies, increased adiabatic compression heating from subsidence, and positive shortwave radiation anomalies due to the reduced cloud cover. The local anomalous anticyclone over the TP is attributed to an atmospheric wave train propagating along the subtropical Asian jet and the sea surface temperature (SST) anomalies related to the Indian Ocean subtropical dipole mode (IOSD). Further analysis indicates that the atmospheric wave train propagating along the subtropical Asian jet is driven by transient eddy feedback and SST anomalies in the equatorial eastern Pacific. In addition, cold SST anomaly in the central and eastern tropical southern Indian Ocean related to the IOSD suppresses convection and diabatic heating, which triggers an upper tropospheric Gill-type pair circulation anomaly straddling the equatorial central-western Indian Ocean. The northern lobe of this anomalous circulation excites a wave train that propagates northeastward to the TP, resulting in an anomalous anticyclone over this region.