Response of Boreal Winter Atmospheric Blocking to Topographic Forcing Induced by the Tibetan–Iranian Plateau

Employing orographic perturbation experiments from a state‐of‐the‐art climate model, this study investigates the topographic forcing associated with the Tibetan–Iranian Plateau (TIP) in modulating Northern Hemisphere boreal winter blocking frequency. The results show that TIP‐related topographic forcing profoundly impacts blocking frequency, with distinct roles of mechanical and thermal components. The increased hemispheric‐mean blocking under full TIP‐related topographic forcing is dominantly attributed to its mechanical forcing, while localized slight reductions stem from its thermal forcing. In general, the response of Northern Hemisphere winter blocking to TIP‐related topographic forcing is dominated by mechanical forcing. TIP‐related mechanical forcing favors blocking occurrence, particularly over Europe and the Ural region, via strengthened stationary waves and positive geopotential height tendencies induced by weakening synoptic‐scale transient eddies. In addition, decelerating background westerly wind and reducing the meridional gradient of potential vorticity also provide favorable conditions for the formation of blocking. In contrast, TIP‐related thermal forcing mildly suppresses North Pacific blocking, primarily through weakened stationary waves and altered background lower‐level temperatures.