Large-scale circulation anomalies associated with persistent low temperature over Southern China in January 2008

2011 ◽  
Vol 12 (3) ◽  
pp. 273-280 ◽  
Author(s):  
Cholaw Bueh ◽  
Ning Shi ◽  
Zuowei Xie
Keyword(s):  
Low Temperature ◽  
Large Scale ◽  
Southern China ◽  
Large Scale Circulation ◽  
Circulation Anomalies

Large-Scale Circulation Anomalies Associated with Extreme Heat in South Korea and Southern–Central Japan

2020 ◽  
Author(s):  
Ke Xu
Keyword(s):  
South Korea ◽  
East Asia ◽  
Large Scale ◽  
Extreme Heat ◽  
Central Japan ◽  
Large Scale Circulation ◽  
Westerly Jet ◽  
Anomalous Anticyclone ◽  
Wave Trains ◽  
Circulation Anomalies

<p>    The large-scale circulation anomalies associated with extreme heat (EH) in South Korea and southern–central Japan are examined using data during the time period 1979–2016. Statistical analysis indicates that EH days in these two regions are concentrated in July and August and tend to occur simultaneously. These EH days are therefore combined to explore the physical mechanisms leading to their occurrence. The composite results indicate that the anomalous atmospheric warming during EH days is dominantly caused by a significant subsidence anomaly, which is associated with a deep anomalous anticyclone over East Asia. Further investigation of the evolution of circulation anomalies suggests that the anomalous anticyclone over East Asia related to EH is primarily initiated by wave trains originating from upstream regions, which propagate eastward along the Asian westerly jet in the upper troposphere. These wave trains can be categorized into two types that are characterized by the precursor anticyclonic and cyclonic anomalies, respectively, over central Asia. The distinction between these two types of wave train can be explained by the wavenumbers of the Rossby waves, which are modulated by both the intensity and the shape of the Asian westerly jet as the background basic flow.</p>

The impact of large-scale circulation on daily fine particulate matter (PM2.5) in major populated regions of China during winter 

2021 ◽  
Author(s):  
Zixuan Jia ◽  
Ruth Doherty ◽  
Carlos Ordóñez ◽  
Chaofan Li ◽  
Oliver Wild
Keyword(s):  
Particulate Matter ◽  
Relative Humidity ◽  
Large Scale ◽  
Southern China ◽  
East Asian ◽  
River Delta ◽  
Large Scale Circulation ◽  
East Asian Trough ◽  
Siberian High ◽  
Pollution Episodes

<p>With rapid economic growth and urbanization, air pollution episodes with high levels of particulate matter (PM<sub>2.5</sub>) have become common in China. While emissions of pollutant precursors are important, meteorology also plays a major role in pollution episodes, especially in winter. We examine the influence of the dominant large-scale circulation and the key regional meteorological features on PM<sub>2.5</sub> over three major regions of China: Beijing–Tianjin–Hebei (BTH), the Yangtze River Delta (YRD), and the Pearl River Delta (PRD). The East Asian winter monsoon (EAWM) is primarily studied, including some of its main large-scale components such as the East Asian trough and the Siberian high, as it influences PM<sub>2.5 </sub>differently in different parts of China. In the BTH region, the shallow East Asian trough curbs the invasion of northerly cold and dry air from the Siberian high which induces high relative humidity and heavy pollution, possibly via relative humidity-promoted aerosol formation and growth. A weak southerly wind in Eastern and Southern China associated with a weakened Siberian high suppresses horizontal dispersion, contributing to pollution accumulation over YRD. In addition, the El Niño-Southern Oscillation (ENSO) as the dominant mode of global ocean-atmosphere interaction has a substantial modulation on precipitation over southern China. In the PRD, weak southerly winds and precipitation deficits over southern China are conducive to atmospheric pollution possibly via reduced wet deposition. Furthermore, we construct new circulation-based indices based on the dominant large-scale circulation: a 500 hPa geopotential height-based index for BTH, a sea level pressure-based index for YRD and an 850 hPa meridional wind-based index for PRD. These three indices can effectively distinguish different levels of pollution over BTH, YRD and PRD, respectively. We also show how additional regional meteorological variables can improve the prediction of regional PM<sub>2.5</sub> concentrations for these three regions. These results are beneficial to understanding and forecasting the occurrence of severely polluted days for BTH, YRD and PRD from a large-scale perspective.</p>

scholarly journals Interannual and Interdecadal Variability of the Number of Cold Days in Hong Kong and Their Relationship with Large-Scale Circulation

2015 ◽  
Vol 143 (4) ◽  
pp. 1438-1454 ◽  
Author(s):  
Hoffman H. N. Cheung ◽  
Wen Zhou ◽  
Sai-ming Lee ◽  
Hang-wai Tong
Keyword(s):  
Hong Kong ◽  
Large Scale ◽  
Polar Region ◽  
East Asian Winter Monsoon ◽  
Southern China ◽  
Winter Monsoon ◽  
Large Scale Circulation ◽  
Meridional Gradient ◽  
Asian Winter Monsoon ◽  
The Past

Abstract During the past decade (2004/05–2013/14), the number of cold days in Hong Kong (NCD), as a proxy of the temperature of southern China, appeared to have increased from the historical minimum, in contrast to a remarkable decline in the entire postwar period. This is related to the recent apparent changes in the large-scale circulation upstream and downstream of the East Asian winter monsoon (EAWM) region: the increase in Ural blocking (UB) that enhances cold advection from the polar region and reinforces the Siberian high and the decrease in a western Pacific (WP)-like index that corresponds to increasing meridional gradient of geopotential height over the EAWM region. Overall, UB and WP account for 26.4% of the interannual (≤8 yr) variance and 83.7% of the decadal (>8 yr) variance of NCD for the period 1948/49–2013/14, indicating that further study could lead to improvement in the prediction of NCD.

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