The 10-30-day intraseasonal variation of the East Asian winter monsoon: The temperature mode

- The leading winter temperature modes have a dominant period of 10 to 30 days in eastern Asia.
- The AO anomaly is closely related to the temperature of the EAWM on the intraseasonal scale.
- The ladder terrain of eastern Asia has an important influence on the surface air temperature ISOs.

East Asia is known for its monsoon characteristics, but little research has been performed on the intraseasonal time scale of the East Asian winter monsoon (EAWM). In this paper, the extended reanalysis (ERA)-Interim sub-daily data are used to study the surface air temperature intraseasonal oscillation (ISO) of the EAWM. The results show that the air temperature (2-m level) of the EAWM has a dominant period of 10-30 days. Lake Baikal and south China are the centers of the air temperature ISO. An anomalous low frequency (10-30-day filtered) anticyclone corresponds to the intraseasonal cold air. The 10-30-day filtered cold air spreads from Novaya Zemlya to Lake Baikal and even to South China. The ISO of the Arctic Oscillation (AO) index influences the temperature of the EAWM by stimulating Rossby waves in middle latitude, causing meridional circulation, and eventually leads to the temperature ISO of the EAWM. RegCM4 has good performance for the simulation of the air temperature ISO. The simulated results indicate that the plateau is responsible for the southward propagation of the intraseasonal anticyclone. The anticyclone could not reach South China when there was no plateau in western China and its upper reaches.