Linkage of the surface air temperature over Tibetan Plateau and Northeast hemisphere in winter at interannual timescale

The interannual variability of surface air temperature (SAT) over the Tibetan Plateau (TP) and its linkage to the SAT over Northeast hemisphere in winter were investigated using monthly mean SAT data. Results show that winter SAT displays consistent interannual variability over the entire TP, with a significant positive correlation (r = 0.43) with SAT over North Africa (NA) and a negative correlation (r = −0.48) with SAT over Siberia (SB). The abnormally high NA SAT causes increased SAT over the Mediterranean, triggering a Rossby wave train propagating to the TP in the upper troposphere. Ascending 300 hPa geopotential height (HGT) anomalies occur over the TP, causing abnormally high TP SAT. The negative SB SAT anomaly is accompanied by a strong negative 300 hPa HGT anomaly with westerly wind effects in the upper troposphere over the northern TP, favoring abnormal anticyclonic circulation. The anticyclonic circulation caused by the two regions strengthens descending motion with adiabatic heating of the air. The relationship between TP and NA and SB SAT levels changed abruptly in the 1990s, with the Rossby wave propagating to the TP after 1990 and stopping near 60°E before 1990. The subtropical westerly anomaly in the southern TP weakened anticyclonic circulation after 1990, with a significant easterly effect before 1990.