Two spatial types of North China heatwaves and their possible links to Barents‐Kara Sea ice changes

Abstract

Heatwaves of different spatial types can cause various impacts. Based on the spatial heatwave intensity, 47 North China heatwaves from 1961 to 2019 could be classified into two categories: the S‐type with a centre in the south and the N‐type in the north. There were more N‐type events (36) than the S‐type (11). Observational analysis indicated that under atmospheric circulations favourable to North China heatwaves (e.g. the enhanced continental high), there is a linkage between the sea ice concentration (SIC) changes in the Barents‐Kara Sea (BKS) and these two types of heatwaves. Relative to high BKS SIC, the reduction of SIC would strengthen the cyclonic circulation over the Siberian‐BKS, which could coordinate with the continental high to enhance the cyclonic over the Jianghuai region. A cyclonic‐anticyclonic‐cyclonic pattern is present over the BKS‐North China‐Jianghuai. The cyclonic circulation over the Jianghuai region would push the continental high northerly, resulting in the heatwave centre to the north. It would also cause favourable conditions for precipitation over southern North China, reducing temperatures and raising soil moisture, not conducive to the heatwave. Therefore, the heatwave intensity in southern North China would weaken and the heatwave centre would locate in the north, making the N‐type. Conversely, when the BKS SIC increases, the upper cyclonic over the Siberian‐BKS would not get strengthened, indicating entire North China would be controlled by continental high, and the heatwaves would be southerly relative to the N‐type, namely the S‐type. A series of numerical experiments using NCAR CAM5.3 confirm the above observational results, whereby if the BKS SIC reduces (increases), the North China heatwave is likely to be the N‐type (S‐type).

Increasing heatwave with associated population and GDP exposure in North China

“…The area of 35°–45°N, 110°–120°E within China is defined as North China (Figure S1), consistent with previous studies (Zhang et al, 2020b, 2022). This region includes Beijing, Tianjin, Hebei, Shanxi, as well as parts of Inner Mongolia and Shandong.…”

“…Super heatwaves in 2021 killed more than 500 people and caused 180 wildfires across North America (Schiermeier, 2021). Heatwaves in China also resulted in serious negative impacts (Cai et al, 2021; Zhang et al, 2022). The 2013 heatwave led to about 160 deaths in Shanghai, and many provinces experienced unprecedented heatwaves costing about $10 billion in damages (Sun, 2014).…”

Current AMO mitigating extreme high temperatures in Central Asia under global warming

“…For example, as global warming intensifies, Arctic Sea ice will decrease significantly, and its potential impact on climate changes in the middle and high latitudes of the Northern Hemisphere will increase during the summer months. Several studies have found that warm‐season Arctic Sea ice may be linked to the teleconnection wave trains over Eurasia through meridional anomalous circulation patterns, affecting extreme climate events at middle and high latitudes (Zhang et al, 2022). Some studies also suggest that there exist SST anomalies at high latitudes responding to overlying atmospheric anomalies, which means that the atmosphere could force SST (Chen et al, 2016; Wu & Chen, 2020).…”

“…Based on the daily maximum temperature (Tmax), we used the 95th percentile of Tmax of the study period as the threshold ( Tx95 ) to select EHT days for each grid in CA (Meehl & Tebaldi, 2004; Zhang et al, 2022). An EHT event is recognized to occur when Tmax exceeds Tx95 .…”

“…In terms of atmospheric circulations, surface air temperature increases are generally caused by upper anticyclonic anomalies, which can warm the near‐surface by adiabatic heating and cause vertical downward anomalies, reducing cloud cover to enhance the solar radiation reaching the ground (Deng et al, 2018; Gershunov et al, 2009; Yang et al, 2021a; Zhang et al, 2020; Zhang et al, 2022). Several studies have pointed out that the enhanced anticyclonic anomaly over northern China (continental high pressure) caused extreme heatwaves (Li et al, 2020a; Yang et al, 2021a; Zhang et al, 2018; Zhang et al, 2020), and similar results were found in Europe (Deng et al, 2018; Yang et al, 2021b).…”