Decadal changes in summer precipitation over arid northwest China and associated atmospheric circulations

As global warming has progressed, precipitation patterns over arid Northwest China have undergone significant change. In this study, changes in summer (JJA) precipitation over the eastern part of Northwest China (ENWC) from 1980 to 2014 were investigated using the China gridded monthly precipitation dataset (CN05.1). The results showed that summer precipitation over the ENWC experienced a decadal wet‐to‐dry shift in 1998. Westerlies played an important role in the upper atmospheric levels in terms of water vapour transport; the decadal variations in summer precipitation were principally controlled by the water vapour input from the ENWC's western boundary. In addition, the decadal variations in summer precipitation in the ENWC appear to be associated with a meridional teleconnection around 110°E and a zonal pattern over 45–60°N in the lower troposphere. These two teleconnections led to cyclonic anomalies in the ENWC and enhanced water vapour transport into the ENWC, resulting in above‐normal precipitation during the 1989–1998 decadal period. Further, the warmer (colder) sea surface temperatures (SSTs) observed in the tropical Eastern Pacific correspond to the southward (northward) displacement of the Asian jet stream and a negative (positive) phase of the Silk Road pattern, resulting in a wet (dry) ENWC. Moreover, the SST anomalies in the North Atlantic and Northwest Pacific may affect summer precipitation over the ENWC via a zonal teleconnection in the middle troposphere.

Section: Resultsmentioning

confidence: 98%

Decadal change in summer precipitation over the east of Northwest China and its associations with atmospheric circulations and sea surface temperatures

Shang

Zhu

et al. 2019

“…Observations show that precipitation has been increasing continuously since the past half century in NWC (Zhai et al ., 2005; Shi et al ., 2007). Many studies have been performed to explore the possible factors for this climate change (Zhou and Huang, 2010; Chen and Huang, 2012; Huang et al ., 2015; Zhou and Wu, 2015; Li et al ., 2016; Li and Ma, 2018; Wu et al ., 2019; Shang et al ., 2020). Zhao et al .…”

Section: Introductionmentioning

confidence: 99%

“…Observations show that precipitation has been increasing continuously since the past half century in NWC (Zhai et al, 2005;Shi et al, 2007). Many studies have been performed to explore the possible factors for this climate change (Zhou and Huang, 2010;Chen and Huang, 2012;Huang et al, 2015;Zhou and Wu, 2015;Li et al, 2016;Li and Ma, 2018;Wu et al, 2019;Shang et al, 2020). Zhao et al (2014) revealed an indirect but important impact of the South Asian summer monsoon on summer rainfall increases over the Tarim Basin by inducing middle and upper tropospheric cooling over central Asia.…”

mentioning

confidence: 99%

Enhanced moisture transport associated with the interdecadal change in winter precipitation over Northwest China

Yin

Zhou

2021

In this study, the interdecadal increase in winter precipitation in northwest China (NWC) since the late 1980s and the associated moisture flux transport are investigated. The results show that an interdecadal change in moisture flux transport also occurred in the late 1980s, resulting in anomalous moisture transport convergence over NWC. The examination of boundary moisture transport shows enhanced incoming net moisture flux transport over NWC after the late 1980s. The zonal and meridional components both play a key role in the net moisture flux transport, with increased incoming transport from the western boundary dominated and followed by increased incoming transport from the southern boundary. The circulation responsible for the moisture flux transport anomalies is a Eurasian (EU)‐like teleconnection over mid‐to‐high latitudes of the Eurasian continent. The EU teleconnection pattern transformed from a positive phase to a negative phase in the late 1980s. The related anomalous cyclone over central Asia and the anomalous anticyclone over Japan result in westerly anomalies to the west of NWC and southeasterly anomalies to the east, respectively. Together, these anomalies enable an enhanced net gain of moisture transport and the anomalous moisture transport convergence over NWC. The enhanced moisture supply, strengthened upward movement and anomalous convergence result in an interdecadal increase in winter precipitation in NWC. In addition, the transition of the EU teleconnection is likely attributed to changes in the zonal mean wind. Sea surface temperature warming in the North Atlantic and northwestern Pacific regions also play a role in the change in the EU teleconnection pattern.

“…The significant regional variability of heavy rainfall climatology has also been found in the United States (Hitchens et al ., 2013), India (Deshpande et al ., 2012), Germany (Zolina et al ., 2008) and elsewhere. The strengthening of the West Pacific Subtropical High (WPSH) and the North America Subtropical High (NASH) after the mid‐1980s was considered as an important factor for the increasing trend of rainfall in Northwest China (Li et al ., 2016; Zhang et al ., 2017; Li and Ma, 2018), with higher wetting trends over mountainous regions (Wang et al ., 2019). Studies on the summer heavy rainfall over the YRB during 1960–2011 indicated that most rainfall indices decreased, but the maximum daily rainfall increased in most locations (Gao and Wang, 2017), which resulted in increases in drought or flood disasters.…”

Section: Introductionmentioning

confidence: 99%

A 40‐year climatology of summer heavy hourly rainfall over mountainous Shanxi in China

Dong

Zhang

2021

In this study, a statistical analysis of the spatiotemporal characteristics of summer heavy hourly rainfall (HHR) events during 1979–2018 over mountainous Shanxi Province is performed in order to examine regional climate change over such a transition region between North China and Northwest China. Results show that the regional 40‐year annual mean summer rainfall is about 272 mm, about 37% of which is associated with HHR events. High‐frequency and high‐intensity HHR events tend to take place in eastern mountainous subregions, whereas most basin subregions experience HHR events with low frequency and low intensity, showing the important influences of local topography and its interaction with prevailing large‐scale flows. The important topographical influences are also reflected by the observations that most mountainous subregions exhibit a major late‐afternoon peak with a secondary early morning maximum, and that the associated diurnal variations are much greater in amplitude than those in basin subregions. It is found that the regional total annual summer rainfall has a decreasing trend during the first 20 years, mostly by non‐HHR contributions, but a rapid increasing trend during the recent 20 years, with dominant HHR contributions. Most subregions with the increasing trends of HHR frequency are those dominated by rapidly increasing surface temperatures. In particular, more frequent HHR events occur over major urbanization areas, that are in close proximity to complex topography, during the recent two decades. The decadal trends in HHR are found to be correlated to the distribution and intensity changes of the East Asian summer monsoon. The above results have important implications to the operational prediction of HHR events, and a better understanding of regional climate change over mountainous Shanxi Province.