scholarly journals Influence of Arctic Oscillation on Frequency of Wintertime Fog Days in Eastern China

Atmosphere ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 162
Author(s):  
Peng Liu ◽  
Mingyue Tang ◽  
Huaying Yu ◽  
Ying Zhang
Keyword(s):  
Water Vapor ◽  
South China ◽  
Arctic Oscillation ◽  
North China ◽  
Eastern China ◽  
Reanalysis Data ◽  
Positive Phase ◽  
Westerly Jet ◽  
Environmental Prediction ◽  
Fog Days

The influence of Arctic Oscillation (AO) on the frequency of wintertime fog days in eastern China is studied based on the winter AO index, the wintertime fog-day data of national stations in China, and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data from 1954 to 2007. The results show that heavy fog and light fog are more likely to occur during winter in eastern China with the strong interannual variability. During the winter with the positive-phase AO, there are more days of heavy fog in North China but less in South China, while light fog days become more in the whole of eastern China. It is mainly because that when AO is in the positive phase, the pressure in the polar region decreases at 500 hPa; the pressure in East Asia increases anomalously; the East Asian trough decreases; and the low-level westerly jet moves northward, preventing the northwesterly cold air from moving southward. Therefore, the whole eastern China gets warmer and wetter air, and there are more light fog days with the enhanced water vapor. However, the atmosphere merely becomes more towards unstable in South China, where the precipitation increases but the heavy fog days decreases. Nevertheless, heavy fog days increase with the water vapor in North China because of moving towards a stable atmosphere, which is formed by the anomalous downdrafts north of the precipitation center in South China. When AO is in the negative phase, the situation is basically opposite to that in the positive phase, but the variations of the corresponding fog days and circulations are weaker than those in the AO-positive-phase winter, which may be related to the nonlinear effect of AO on climate.

scholarly journals The Combined Effects of ENSO and Arctic Oscillation on Wintertime Fog Days in Eastern China

2021 ◽  
Author(s):  
Huaying Yu ◽  
Peng Liu ◽  
Ying Zhang
Keyword(s):  
South China ◽  
Temperature Rise ◽  
El Niño ◽  
Arctic Oscillation ◽  
North China ◽  
El Nino ◽  
Eastern China ◽  
Combined Effects ◽  
Low Level ◽  
Fog Days

Abstract The data of fog days from weather observation stations in China and the NCEP/NCAR re-analysis data from 1954 to 2007 are used to investigate the combined effects of El Niño and Southern Oscillation (ENSO) and Arctic Oscillation (AO) on the number of winter fog days in eastern China. The results show that during El Niño the enhanced low-level southwesterly warm-moist airflow could lead to the temperature rise and humidity increase in eastern China. Note that the rate of humidity increase is faster than the rate of temperature rise, which makes the air in eastern China easy to be saturated. Besides, in winter the North China is dominated by the sinking airflow, so a large-value area of fog days appears in eastern China with the center in North China. While in La Niña years, the atmospheric circulation and its influence on the fog days are the opposite. During the positive AO period, the East Asian trough weakens and the low-level westerly jet moves northward, preventing northwesterly cold air from moving southward. The warming and humidification of North China and the slight temperature drop in South China would cause more fog days in North China and fewer fog days in South China. The effect of negative AO is opposite to that of positive AO. The combined effects of ENSO and AO are far greater than the sum of their individual effects. Under El Niño and positive AO, the number of fog days would increase significantly in North China during the whole winter. Besides, ENSO has greater impacts than AO during early winter and vice versa during later winter.

Long-term variation of water vapor content and precipitation in the Haihe river basin

2014 ◽  
Vol 6 (2) ◽  
pp. 341-351 ◽  
Author(s):  
Chun Chang ◽  
Ping Feng ◽  
Fawen Li ◽  
Yunming Gao
Keyword(s):  
Water Vapor ◽  
River Basin ◽  
Reanalysis Data ◽  
Water Vapor Content ◽  
Haihe River Basin ◽  
Haihe River ◽  
Annual Water ◽  
Environmental Prediction ◽  
High Consistency ◽  
The Haihe River Basin

Based on the Haihe river basin National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis data from 1948 to 2010 and the precipitation data of 53 hydrological stations during 1957–2010, this study analyzed the variation of water vapor content and precipitation, and investigated the correlation between them using several statistical methods. The results showed that the annual water vapor content decreased drastically from 1948 to 2010. It was comparatively high from the late 1940s to the late 1960s and depreciated from the early 1970s. From the southeast to the northwest of the Haihe river basin, there was a decrease in water vapor content. For vertical distribution, water vapor content from the ground to 700 hPa pressure level accounted for 72.9% of the whole atmospheric layer, which indicated that the water vapor of the Haihe river basin was mainly in the air close to the ground. The precipitation in the Haihe river basin during 1957–2010 decreased very slightly. According to the correlation analysis, the precipitation and water vapor content changes showed statistically positive correlation, in addition, their break points were both in the 1970s. Furthermore, the high consistency between the precipitation efficiency and precipitation demonstrates that water vapor content is one of the important factors in the formation of precipitation.

scholarly journals Interdecadal Variations of Persistent Extreme Heat Events in Eastern China Under Global Warming

2021 ◽  
Author(s):  
Naihui Zang ◽  
Junhu Zhao ◽  
Pengcheng Yan ◽  
Han Zhang ◽  
Shankai Tang ◽  
...  
Keyword(s):  
Global Warming ◽  
21St Century ◽  
South China ◽  
North China ◽  
Eastern China ◽  
Extreme Heat ◽  
Maximum Temperature ◽  
Extreme Heat Events ◽  
June July ◽  
Heat Events

Abstract Persistent extreme heat events (PEHEs) exert a more negative impact on society, including agriculture, plant phenology, power production and human health, compared to general EHEs. The temporal and spatial characteristics of summer PEHEs in eastern China were analysed based on a daily maximum temperature dataset from 759 stations over the period of 1961–2018. The results show the following: Persistent distributions of PEHEs show that they are characterized by an exponential decay with a drop in the decay rate. In terms of spatial distribution, there is an apparent regional difference in the duration of PEHEs. North China is dominated by multi-frequency and short-duration EHEs, while South China is the opposite. PEHEs in North China and the Huanghuai region mainly occur in June-July but mostly in July and August in South China. Strongly responding to global warming, the frequency and duration of PEHEs in North China have increased since the 1990s. However, the frequency of PEHEs in North China and the Huanghuai region has shown opposite trends in June-July since the beginning of the 21st century. Affected by the atmospheric circulations, the regional differences in PEHE frequency are also apparent. Since the beginning of the 21st century, the PEHEs in North China and the Huanghuai area have shown an increasing trend in August. The short-term PEHEs in the middle and lower reaches of the Yangtze River and South China increased rapidly in the 2000s, while long-term PEHEs increased in the 2010s. This study implies that attention should be paid to not only the frequency of EH days but also to the persistence of EHE which is a key characteristic of damaging EH.

scholarly journals The combined effect of two westerly jet waveguides on heavy haze in the North China Plain in November and December 2015

2019 ◽  
Author(s):  
Xiadong An ◽  
Lifang Sheng ◽  
Qian Liu ◽  
Chun Li ◽  
Yang Gao ◽  
...  
Keyword(s):  
East Asia ◽  
Rossby Wave ◽  
South China ◽  
North China Plain ◽  
North China ◽  
Combined Effect ◽  
The North ◽  
Westerly Jet ◽  
The North China Plain ◽  
Subtropical Westerly Jet

Abstract. Severe haze occurred in the North China Plain (NCP) from November to December 2015, with a wide spatial range and long duration. In this paper, the combined effect of two westerly jet waveguides on haze in the NCP was investigated based on visibility observational data and NCEP/NCAR reanalysis data. The results showed that the two Rossby waveguides within the westerly jet originating from the Mediterranean were responsible for the haze formation in the NCP. The Rossby wave propagated eastward along the subtropical westerly jet and the polar front jet, causing an anomalous anticyclone over the Sea of Japan and anticyclonic wind speed shear at 850 hPa over the NCP, which enhanced the anomalous descending air motion in the middle and lower troposphere and subsequently resulted in a stable atmosphere. Furthermore, the Rossby wave weakened the East Asia trough and Ural ridge, and strengthened the anomalous southerly wind at 850 hPa over the coastal areas of east China, decelerating the East Asia winter monsoon. The above meteorological conditions modulated haze accumulation in November and December 2015. Meanwhile, continuous rainfall related to ascending motion due to Rossby wave propagation along the subtropical westerly jet occurred in a large area of southern China. The latent heat released by rainfall acted as a heat source, inducing convection over South China. This further strengthened the ascending motion over South China so that the descending motion over the NCP was maintained, favoring the maintenance of severe haze. This study is of great significance to elucidate the formation and maintenance mechanism of large-scale haze in the NCP in late fall and boreal winter.

Role of Tibetan Plateau in Northern Drought induced by Changes in Subtropical Westerly Jet

2021 ◽  
pp. 1-40
Author(s):  
Qingzhe Zhu ◽  
Yuzhi Liu ◽  
Tianbin Shao ◽  
Run Luo ◽  
Ziyuan Tan
Keyword(s):  
Water Vapor ◽  
Tibetan Plateau ◽  
North China ◽  
Lower Troposphere ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
The Tibetan Plateau ◽  
Westerly Jet ◽  
The Impact ◽  
Subtropical Westerly Jet

AbstractThe Tibetan Plateau (TP), the “Water Tower of Asia”, plays an important role in the water cycle. However, few studies have linked the TP’s water vapor supply with the climate over North China. In this study, we found that changes in the subtropical westerly jet (SWJ) dynamically induce drought in North China, and the TP plays an important role in this relationship. During July-August for the period of 1981-2019, the SWJ center between 75°E and 105°E obviously shifted northward at a rate of 0.04° per year. Correspondingly, the zonal winds in the southern subtropics were incredibly weakened, causing the outflow of water vapor from the TP to decrease dramatically. Combined with numerical simulations, we discovered that a reduction in water vapor transport from the TP can obviously decrease the precipitation over North China. Sensitivity experiments demonstrated that if the water vapor outflow from the eastern border of the TP decreases by 52.74%, the precipitation in North China will decrease by 12.69% due to a decrease in the local cloud fraction caused by a diminished water vapor content in the atmosphere. Therefore, although less water vapor transport occurs in the upper troposphere than in the lower troposphere, the impact of transport from the TP in the former on the downstream precipitation cannot be ignored.

scholarly journals Trends and Variability in Precipitable Water Vapor throughout North China from 1979 to 2015

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Wang Peng ◽  
Xie Tongchuan ◽  
Dai Jiageng ◽  
Sun Jingmin ◽  
Wu Yanling ◽  
...  
Keyword(s):  
Water Vapor ◽  
Inner Mongolia ◽  
North China ◽  
Eastern China ◽  
Precipitable Water ◽  
Precipitable Water Vapor ◽  
Qinghai Province ◽  
Trend Magnitude ◽  
Four Seasons ◽  
Increasing Trends

This study analyzed the variability and trends in precipitable water vapor (PWV) in North China from 1979 to 2015. The spatial distribution of annual mean PWV was generally characterized by two high PWV centers in Eastern China and the Tarim Basin and two low PWV centers in Northern Tibet and Qinghai Province and in Inner Mongolia. The levels of seasonal mean PWV were highest in summer, followed by autumn and spring, and lowest in winter. The maximum monthly mean PWV occurred in July and August, while the minimum occurred in December to February. Increasing trends in PWV, with the trend magnitude ranging from 0.1 to 1.2 mm decade−1 over North China, were observed in the radiosonde, ERA-interim, and MERRA-2 PWV data from 1979 to 1999; but a slightly decreasing trend of −0.4 mm decade−1 from radiosonde was found in most regions of North China from 1979 to 2007. A monotonically increasing PWV trend was detected throughout North China between 1979 and 1999, with the maximum trend occurring in summer and the minimum occurring in winter. For the period of 1979–2007, a slightly but less marked decreasing trend was found at most stations in North China in all four seasons.

scholarly journals Different Roles of Water Vapor Transport and Cold Advection in the Intensive Snowfall Events over North China and the Yangtze River Valley

Atmosphere ◽  
2019 ◽  
Vol 10 (7) ◽  
pp. 368 ◽  
Author(s):  
Zhixing Xie ◽  
Bo Sun
Keyword(s):  
Water Vapor ◽  
Yangtze River ◽  
North China ◽  
Dominant Role ◽  
Eastern China ◽  
Yangtze River Valley ◽  
River Valley ◽  
Vapor Transport ◽  
Water Vapor Transport

Intensive snowfall events (ISEs) have a profound impact on the society and economy in China during winter. Considering that the interaction between northerly cold advection and southerly water vapor transport (WVT) is generally an essential condition for the occurrence of ISEs in eastern China, this study investigates the different roles of anomalous southerly WVT and northerly cold advection during the ISEs in the North China (NC) and Yangtze River valley (YRV) regions based on a composite analysis of seventy ISE cases in NC and forty ISE cases in the YRV region from 1961 to 2014. The results indicate that the ISEs in NC are mainly associated with a significant pre-conditioning of water vapor over NC induced by southerly WVT anomalies over eastern China, whereas the ISEs in the YRV region are mainly associated with a strengthened Siberian High (SH) and strong northerly cold advection invading the YRV region. These results suggest a dominant role of anomalous southerly WVT in triggering the ISEs in NC and a dominant role of northerly cold advection in triggering the ISEs in the YRV region. The different roles of anomalous southerly WVT and northerly cold advection in the ISEs over the NC and YRV regions are largely attributed to the different winter climate in the NC and YRV regions—during winter, the NC (YRV) region is dominated by cold and dry (relatively warm and moist) air flow and hence southerly WVT (northerly cold advection) is the key factor for triggering the ISEs in NC (the YRV region).

Palaeomagnetism, North China and South China collision, and the Tan-Lu fault

1990 ◽  
Vol 331 (1620) ◽  
pp. 589-598 ◽  
Keyword(s):  
South China ◽  
North China ◽  
Eastern China ◽  
Early Jurassic ◽  
Late Triassic ◽  
Polar Wander ◽  
The North ◽  
Indosinian Orogeny ◽  
North And South ◽  
Transcurrent Faults

Refined Apparent Polar Wander (APW) paths for the North and South China Blocks (ncb and scb) are presented and the collision between the NCB and SCB discussed. We suggest that the amalgamation of the NCB and SCB was completed in the late Triassic-early Jurassic, during the Indosinian Orogeny. This proposed timing is based on an analysis of palaeomagnetic signatures relating to continental collisions, such as the convergence of palaeolatitude, deflections of declination, hairpin-like loops in and superposition of APW paths. Like the Cenozoic India—Eurasia collision, the Mesozoic NCB- SCB collision reactivated ancient faults in eastern China, converting some of them into transcurrent faults, of which the Tan-Lu fault is the most famous.

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