Predictability of the prolonged spring-summer heat and dry extremes over Northeast China in 2017

There was a severe drought accompanied by extreme heat in Northeast China from spring to summer in 2017. It was the largest event since 1961 and caused huge damage to agricultural and industrial production, with a direct economic loss of more than 70 billion RMB. However, the main causes for the long-term persistent heat and dry extreme event and its predictability are still unclear. In this study, we investigate the underlying dynamic mechanisms of the persistent spring-summer hot drought over Northeast China, and further evaluate the prediction skill for the extreme event. Previous studies have indicated that when El Niño evolves synergistically with Eurasian spring snow reduction, a positive summer Eurasia teleconnection (EU) pattern will be triggered and may lead to severe droughts in North China, such as the 2015 summer drought. We have found that the prolonged extreme event in 2017 was associated with extensive and sustained Baikal High. But the background circulation and physical mechanisms of this extreme event are quite different from the 2015 extreme summer drought and may lead to different seasonal predictability. In addition, we also compared the prediction skill of the water vapor transport based on CFSv2 real-time seasonal forecast for the extreme events, which is targeted at providing information for drought adaptation.