Yuan Yuan

The 24th Olympic and Paralympic Winter Games will take place in Beijing in 2022. All three competition zones are vulnerable to extreme cold surges (ECSs), owing to the occurrence of the East Asian winter monsoon. In this paper, a representative competition domain (37.5–42.5° N, 110–120° E) is adopted, with a view to avoiding the differences in both the geographies and the thresholds of ECSs among different zones by considering the probability of simultaneous occurrences. Since 2009, the ECSs in the domain have displayed higher frequency and extremity. Based on all ECS cases in the domain, the dominant circulation is revealed by a quasi “reverse-Ω” pattern, with two strong ridges over the east of the Ural Mountain and the Okhotsk Sea, and a broad, deep trough in East Asia. The influencing sources of the ECSs at the domain could be traced to the Novaya Zemlya by a day-by-day backward analysis. The oblique latitude/longitude–time profiles of both the 500 hPa geopotential height and the 850 hPa air temperature anomalies from the source to the domain clearly indicate that the pre-signal could have a leading influence that exceeds ten days, with a slow accumulation in the first stage and a rapid outburst in the second stage.

This study investigates the relationship between the summer high temperature in northern China and the northern North Atlantic (NNA) sea surface temperature anomalies (SSTAs) in the previous winter and spring during the period 1981–2017. In northern China, mean maximum temperature (T_max) above 31°C and high frequencies of hot days are concentrated in June–July. SSTAs in the NNA in the previous December–April have a significant positive relationship with the mean T_max from the Yellow River Basin to the north of the Yangtze River in June–July, and this significant positive correlation still exists after removing the trends. Correlation and composition analysis suggests that the NNA SST and high temperature in northern China are connected by the mid‐latitude wave‐train circulation anomalies across the Atlantic and Europe. Warm SSTAs in the NNA in winter and spring favour anticyclonic circulations in the NNA, Western Europe and the south of Lake Baikal, and cyclonic circulations in the northeastern North Atlantic and the Ural Mountains. The positive height anomaly and anticyclonic circulation in the south of Lake Baikal tend to result in downward motion and high temperature in northern China. The linkage between winter–spring North Atlantic SST and high temperature can be used to facilitate seasonal prediction of extreme high temperature in China.

In July–August (JA) 2018, the western Pacific subtropical high (WPSH) was stronger than normal. Its ridge line was located the most north in history and the position was above three times of the standard deviation. On the intra‐seasonal timescale, the high ridge was mostly more north than normal from July 5 till the end of August in 2018 and had two significant northward jumps in the first 10 days and last 5 days of July 2018, respectively. The convective activities in the western Pacific should play an important role in the extremely north WPSH in JA 2018. The convection over the western Pacific was the strongest in JA 2018 during the past 38 years. It induced significant subsidence anomalies, an anomalous low‐level anticyclone and positive anomalies of 500‐hPa geopotential height in eastern East Asia. On the daily timescale, the northward movement of the active convection over the western Pacific occurred about 5 days earlier than the northward jump of the WPSH. Additionally, the strong and long‐lasting Madden–Julian oscillation in the western Pacific (Phase 6) also favoured the suppressed convection and positive anomalies of 500‐hPa geopotential height in eastern East Asia. This result could provide a good precursor signal about 5 days advance for the northward jump of the WPSH in summer.