Seasonal Dependence of Thermal and Dynamical Effects of the Tibetan Plateau and Their Modulations on Atmospheric Circulation

Seasonality of the thermal and dynamical effects of the Tibetan Plateau (TP) on climate is investigated. Model experiments show that thermal effects are dominant in spring and summer, which cause strong rising motion and anomalous warming over the TP. In comparison, dynamical effects exert a much weaker influence on the general circulation in all seasons, except in winter when dynamical effects of the TP play an important role in generating wave patterns, which are related to the interaction between strong westerlies and the terrain. Besides, the thermal and dynamical effects manifest the associated impact on the meridional-vertical circulation, leading to strong rising motion over the TP, especially over the southern part. Furthermore, the thermal effects of the TP significantly strength the South Asian high, the Somali jet stream and the southwesterly monsoon flow over East Asia, but dynamical effects are also linked to the low-level Asian summer monsoon circulation, although they contribute a smaller influence compared to the thermal effects. Moreover, the dynamical effects would lead to a strong convergence over the Indian subcontinent, inducing an obvious increase in precipitation over India.