Diversity in the quasi‐biweekly oscillation sources of the daily maximum temperature over South China during summer

Abstract

AbstractThe summer daily maximum temperature (Tmax) over South China features obvious quasi‐biweekly oscillation (QBWO) and its QBWO sources mainly include three types. The first type is influenced by tropical and mid–high‐latitude antiphase coupling QBWO. Successive suppressed and enhanced convection, accompanying with anticyclonic and cyclonic anomalies, propagate northward from the northwest of the Philippines to South China. At the peak warm phase, an anomalous high dominates over South China and causes significant warming. Meanwhile, an anomalous low associated with a southeastward‐propagating wave train occurs to the north and leading to abnormal cooling in situ. The second type originates from the mid–high latitudes. Before the warm phase, an anomalous high around the Ural Mountains triggers two wave trains propagating southeastward along the great circle route and eastward along the westerly jet, respectively, favouring an anomalous high over North–Northeast China. At the peak warm phase, the anomalous high extends southward, causing significant warming over South–Central China. The third type is influenced by tropical and mid–high‐latitude in‐phase coupling QBWO. The tropical anomalies are similar to the first type but the convection anomalies are centred to the northeast of the Philippines and propagate northwestward. The mid–high‐latitude wave trains are similar to the second type but with relatively weaker southeastward‐propagating wave train. At the peak warm phase, the anomalous highs from the Tropics and mid–high latitudes together dominate a large meridional scope and induce wide‐range warming over eastern China. Intrinsically, the QBWO of the convection north of the Philippines and mid–high‐latitude wave trains are important signals of the atmospheric variability and might be applied to the forecast of South China Tmax.