Strong Contributions of Abnormal Vortex Street-Like System in the Tibetan Plateau’s Wake to Record-Breaking Strong Rainfall over Southern China in April 2024

Abstract In April 2024, southern China experienced unprecedented heavy rainfall, resulting in severe flooding, significant loss of life, and substantial economic damage. However, the underlying causes of this event remain unclear. Our previous research suggests that the rainfall over East Asia is significantly impacted by the vortex street-like system in the Tibetan Plateau’s wake (TPVSL, a phenomenon in the textbook). Thus, we hypothesize that TPVSL may have played a critical role in the extreme rainfall over southern China in April 2024. Using daily observational precipitation, reanalysis, and sea surface temperature data, we analyzed the anomalous circulation linked to this extreme rainfall event from the perspective of the TPVSL. Our findings reveal that TPVSL provided a favorable background for ∼78% of the precipitation during this event. Specifically, the intensity of the TPVSL was abnormally strong, while the vortex propagation speed, shedding period, and propagating line position of the TPVSL remained close to normal. The abnormally strong TPVSL mainly resulted from the unprecedented strong westerly over the southern sides of the Tibetan Plateau, which was caused by an extreme enhancement of the north–south temperature gradient in April. The record-breaking meridional temperature gradient resulted from the preceding strong El Niño event. The preceding strong El Niño event led to the anomalous tropical Indian Ocean warming and anomalous cooling and soil moistening over the Iranian Plateau. Our study underscores the importance of understanding the TPVSL system to mitigate flood disasters.