Role of Sea Surface Temperature over the Kuroshio Extension Region on Heavy Rainfall Events over the Korean Peninsula

This study examines the active role of sea surface temperature (SST) over the Kuroshio Extension region during heavy rainfall events over the Korean Peninsula within Changma period (June–July). While the overall synoptic patterns during the heavy rainfall events over Korea are similar to those during moderate rainfall events (i.e. between 0.5 and 1 standard deviation), the synoptic signals preceding heavy rainfall events are distinct from those of moderate rainfall events. A distinguishing feature is the maintenance of a high-pressure anomaly over the Kuroshio Extension region, which lead to persistent southerly winds and resultant heavy rainfall events over the Korean Peninsula, from roughly 1 week before the start of heavy rainfall events. On the other hand, the high-pressure anomaly associated with the moderate rainfall events is propagated from the west along the climatological westerly winds. It was found that positive SST anomalies over the Kuroshio Extension region (140–156°E, 28–35°N) play an important role in maintaining the high-pressure anomaly over the Kuroshio Extension region. None of heavy rainfall events was found when the positive geopotential height anomaly over the Kuroshio Extension region was co-located with a local negative SST anomaly. This probability increased to 62% when the positive geopotential height anomaly was co-located with a local positive SST anomaly. This shows that a positive SST anomaly over the Kuroshio Extension region can be a useful precursor to heavy rainfall events over the Korean Peninsula.