LAUSR

The intensity and location of boreal summer extratropical intraseasonal oscillations along the subtropical westerly jet (EISO-SJ) are crucial in triggering and distributing extreme events over Eurasia. Based on numerical experiments, this study distinguishes the orographic mechanical and surface thermal forcing of Tibetan-Iranian Plateau (i.e., TIP-MF and TIP-TF) on EISO-SJ. The TIP-MF primarily modulates the amplitude of EISO-SJ that strengthens over the upstream and weakens over downstream. Comparatively, the TIP-TF not only reduces/increases the intensity of EISO-SJ over the TIP upstream/downstream, but also significantly migrates the track of EISO-SJ northward. Further analysis demonstrates that the changes of westerly jet, eddy energy propagation and energy conversion are consistent with the track and amplitude changes of EISO-SJ. This study indicates the variations of TIP surface sensible heating in interannual variation and global change as well as the terrain uplift of TIP in paleoclimate influence the mid-latitude subseasonal variation.