Contrasting seasonal variations between the genesis frequency and intensity of Tibetan Plateau vortices

Precipitation over the Tibetan Plateau (TP) is vital to regional and surrounding water resources. TP vortices (TPVs) are major precipitation systems over the TP, often inducing heavy precipitation locally and in downstream East Asia. This work reports a novel discovery that pronounced contrasting seasonal variations occur in the genesis frequency and intensity of TPVs. More TPVs occur in warm season (May–September) and less in cold season (October–April), while TPV intensity follows a contrasting pattern. During the seasonal cycle over the TP, the strongest cyclonic convergence (divergence) ascending (descending) motion, diabatic heating (cooling) in warm (cold) season, contribute to more TPVs in warm season, and less in cold season. However, temperature changes during the seasonal cycle are vertically different, producing seasonal different vertical temperature gradient, and thereby resulting in weak TPVs in warm season and strong in cold season.