In recent years, wintertime warm blobs over the Northeast Pacific (NEP), featuring persistent and intense upper-level ocean warming, have attracted wide attention, with many studies focused on their spatiotemporal characteristics, mechanisms, and climate effects. However, the summer warm blob events have received much less attention. Current studies did not reach a consensus on their formation mechanisms and climate impacts. Based on sea surface temperature data from 1948 to 2023, this study identifies 12 summer (June–July–August) warm blob events, which are largely dominated by surface heat flux anomalies based on a mixed-layer heat budget analysis. These events are associated with enhanced precipitation over the blob area and reduced rainfall along the Alaskan coast at the peak time, while the coastal rainfall is reversed into positive anomalies after the peak, which favors the formation of Rossby wave due to the circulation anomalies. Hence, the upper-level circulation and 2-meter temperature fields exhibit a wave train signature extending across North America and Eurasia. Specifically, there is a dipole over North America, showing a pattern of positive in the west and negative in the east. Over Eurasia, the negative-positive-negative wave-like distribution is found over Europe, high-latitude central Eurasia, and Northeast China, respectively. The downstream wave train response due to the NEP warm blob forcing is qualitatively verified by the Linear Baroclinic Model. This study advances understanding of the climate significance of summer warm blobs on surface temperature anomalies in mid- to high-latitude regions.
Chen et al. (Thu,) studied this question.