An extratropical window of opportunity for subseasonal prediction of East Asian summer surface air temperature

Abstract

Previous studies suggest that boreal summer intraseasonal variations along the subtropical westerly jet (SJ), featuring quasi-biweekly periodicity, frequently modulate downstream subseasonal variations over East Asia (EA). Based on subseasonal hindcasts from six dynamical models, this study discovered that the leading two–three-week prediction skills for surface air temperature (SAT) are significantly higher in summer with stronger intraseasonal oscillation along the SJ, which are best demonstrated over the eastern Tibetan Plateau, Southwest Basin, and North China. The reasons are that the enhanced quasi-biweekly wave and its energy dispersion along the SJ cause more regular quasi-biweekly periodic variations of downstream SAT, which potentially increase regional predictability. This study suggests that the strengthened intraseasonal periodic signals along the SJ would enhance the subseasonal predictability in downstream regions, which could provide a window of opportunity for achieving better subseasonal prediction for EA SAT.