The relationship between heat wave events over central eastern China and atmospheric quasi-biweekly oscillation

Abstract:

The relationship between East China heat wave (HW) events and atmospheric quasi-biweekly variability (QBW) has been investigated in this study. HW has its maximum frequency over central eastern China. Over the core region (26°-31°N, 112°-117°E), there are 59 dry HW events occurrence during the past 34 years (1979-2012). Among 59 HW events, 23 events are associated with the dry phase of QBW. The dry phase of QBW corresponds to the low-level anticyclonic anomaly, upper-level cyclonic anomaly and anomalous descent over the HW core region. The circulation anomalies cause the westward extension of the western Pacific subtropical high (WPSH) and results in extreme dry HW. Further analysis found that the generation of the QBW over the HW core region was associated with both a northwestward propagation of tropical low-level disturbances and an eastward propagation of mid-latitude upper-level disturbances along westerly jet. We also found that the HW frequency over the core region increased from 1.14 times/year to 2.83 times/year, which was essentially attributed to the growth of QBW-associated HW events.