Early signals of synoptic-scale atmospheric anomalies associated with the summer low temperature events in Northeast China

Abstract

Following a description of the climatology of the boreal summer persistent low temperature (LT) events of the Northeast (NE) China, this paper explores the synoptic characteristics of these events by decomposing atmospheric variables into three components: the daily climate, the zonal-averaged anomaly and the synoptic-scale anomaly. The synoptic-scale anomaly is used to construct the anomalous synoptic charts which tend to perform better compared to traditionally defined synoptic charts in terms of revealing synoptic characteristics of these LT events. Based on the analysis of 21 persistent LT events occurring during summers of 1961–2008 in NE China, we show that temperature anomaly at 850 hPa and geopotential height anomaly at 300 hPa were two critical early signals prior to the occurrences of these persistent LT events.