scholarly journals Study on a Large-Scale Persistent Strong Dense Fog Event in Central and Eastern China

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Hongbin Wang ◽  
Zhiwei Zhang ◽  
Duanyang Liu ◽  
Yuying Zhu ◽  
Xuerong Zhang ◽  
...  
Keyword(s):  
Large Scale ◽  
Eastern China ◽  
Inversion Layer ◽  
Reanalysis Data ◽  
Radiation Fog ◽  
Large Intensity ◽  
Long Duration ◽  
Dense Fog ◽  
Fine Resolution ◽  
Radiation Cooling

A large-scale persistent strong dense fog (SDF) event that occurred from December 30, 2016, to January 5, 2017, in central and eastern China is analyzed by using a variety of data, including high-resolution satellite and surface observations, meteorological tower observations, fine-resolution sounding observations, and NCEP/NCAR reanalysis data. The results show the following: (1) The SDF event has the characteristics of long duration, wide influence range, large intensity, and serious air pollution. During the study period, there are 531 stations with SDF events, covering an area of over 360,000 km2. There were five stations in Hebei province where the fog lasted for more than 77 hours, and even some stations did not dissipate during the day. (2) Radiation fog and advection fog alternate in this SDF event, namely, radiation fog (20:00 BT on December 30 to 14:00 on January 1), advection radiation fog (20:00 on January 1 to 08:00 on January 2), radiation fog (night on January 2 to daytime on January 3), and advection radiation fog (night on January 3 to January 5). The characteristic of radiation fog is that the central and eastern part of China was controlled by “L” type high pressure. In the stage of advection radiation fog, the combined effect of weak cold advection and radiation cooling leads to the occurrence of SDF. (3) Regarding the duration of the fog event, the inversion structure is continuously maintained at night and in the morning near the stratum, and when the fog intensity is strong, the inversion intensity is correspondingly large, the fog top is lower than the inversion layer top, and the top of the SDF is between 80 and 400 meters.

scholarly journals A Persistent Fog Event Involving Heavy Pollutants in Yancheng Area of Jiangsu Province

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Yuying Zhu ◽  
Chengying Zhu ◽  
Fan Zu ◽  
Hongbin Wang ◽  
Chengsong Yuan ◽  
...  
Keyword(s):  
General Circulation ◽  
Final Analysis ◽  
Analysis Data ◽  
Reanalysis Data ◽  
Thermal Factor ◽  
Atmospheric General Circulation ◽  
Long Duration ◽  
Low Visibility ◽  
Dense Fog ◽  
Good Visibility

In the early December 2013, dense fog involving heavy pollutants lasted for 9 days in the Yancheng area. The characteristics, formation, and lasting mechanisms of this persistent fog were analyzed based on observational data at the Sheyang site, reanalysis data, and final analysis data from NCEP/NCAR, combining with the weather background and meteorological and physical variable fields. Results include that (1) the fog process was characterized by long duration, low visibility, and high pollutants concentration, (2) the atmospheric general circulation contributed to the sustainability and development of the heavily polluted fog, (3) deep inversion was the key thermal factor causing the heavily polluted fog, (4) the fog exhibited obvious outbreaks with good visibility weather turned to severe fog several times, and (5) the weak cold air invasion and radiative cooling were the triggering factors to the sudden enhancement of the fog.

scholarly journals Residual Circulation and Tropopause Structure

2010 ◽  
Vol 67 (8) ◽  
pp. 2582-2600 ◽  
Author(s):  
Thomas Birner
Keyword(s):  
Large Scale ◽  
Climate Model ◽  
Inversion Layer ◽  
Vertical Gradient ◽  
Static Stability ◽  
Reanalysis Data ◽  
Tropopause Height ◽  
Residual Circulation ◽  
Stratospheric Dynamics ◽  
Extratropical Tropopause

Abstract The effect of large-scale dynamics as represented by the residual mean meridional circulation in the transformed Eulerian sense, in particular its stratospheric part, on lower stratospheric static stability and tropopause structure is studied using a comprehensive chemistry–climate model (CCM), reanalysis data, and simple idealized modeling. Dynamical forcing of static stability as associated with the vertical structure of the residual circulation results in a dominant dipole forcing structure with negative static stability forcing just below the tropopause and positive static stability forcing just above the tropopause. This dipole forcing structure effectively sharpens the tropopause, especially during winter. Furthermore, the strong positive lowermost stratospheric static stability forcing causes a layer of strongly enhanced static stability just above the extratropical tropopause—a tropopause inversion layer (TIL)—especially in the winter midlatitudes. The strong positive static stability forcing is shown to be mainly due to the strong vertical gradient of the vertical residual velocity found just above the tropopause in the winter midlatitudes. Stratospheric radiative equilibrium (SRE) solutions are obtained using offline radiative transfer calculations for a given tropospheric climate as simulated by the CCM. The resulting tropopause height in SRE is reduced by several kilometers in the tropics but is increased by 1–2 km in the extratropics, strongly reducing the equator-to-pole contrast in tropopause height. Moreover, the TIL in winter midlatitudes disappears in the SRE solution in contrast to the polar summer TIL, which stays intact. When the SRE solution is modified to include the effect of stratospheric dynamics as represented by the stratospheric residual circulation, the TIL in winter midlatitudes is recovered, suggesting that the static stability forcing associated with the stratospheric residual circulation represents the main cause for the TIL in the winter midlatitudes whereas radiation seems dominant in causing the polar summer TIL.

scholarly journals Classification of summertime synoptic patterns in Beijing and their association with boundary layer structure affecting aerosol pollution

2016 ◽  
Author(s):  
Yucong Miao ◽  
Jianping Guo ◽  
Shuhua Liu ◽  
Huan Liu ◽  
Zhanqing Liu ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Layer Structure ◽  
Inversion Layer ◽  
Principal Component ◽  
Near Surface ◽  
Synoptic Patterns ◽  
Synoptic Conditions ◽  
Aerosol Pollution ◽  
Fine Resolution

Abstract. Meteorological conditions within the planetary boundary layer (PBL) are closely governed by large-scale synoptic patterns and play important roles in air quality by directly and indirectly affecting the emission, transport, formation, and deposition of air pollutants. Partly due to the lack of long-term fine-resolution observations of the PBL, the relationships between synoptic patterns, PBL structure, and aerosol pollution in Beijing have not been well understood. This study applied the obliquely rotated principal component analysis in T-mode to classify the summertime synoptic conditions over Beijing using the National Centers for Environmental Prediction reanalysis from 2011 to 2014, and investigated their relationships with PBL structure and aerosol pollution by combining measurements of surface meteorological variables, fine-resolution soundings, the concentration of particles with diameters less than or equal to 2.5 μm, total cloud cover (CLD), and reanalysis data. Among the seven identified synoptic patterns, three types accounted for 67 % of the total number of cases studied and were associated with heavy aerosol pollution events. These particular synoptic patterns were characterized by high-pressure systems located to the east or southeast of Beijing at the 925-hPa level, which blocked the air flow seaward, and southerly PBL winds that brought in polluted air from the southern industrial zone. In the vertical dimension, these three synoptic patterns featured a relatively low boundary layer height (BLH) in the afternoon, accompanied by high CLD and southerly cold advection from the seas within the PBL. The cold advection induced by the large-scale synoptic forcing may have cooled the PBL, leading to an increase in near-surface stability and a decrease in the BLH in the afternoon. Moreover, when warm advection appeared simultaneously above the top level of the PBL, the thermal inversion layer capping the PBL may have been strengthened, resulting in further suppression of the PBL and deteriorating aerosol pollution levels. This study has important implications for understanding the crucial roles that meteorological factors (at both synoptic and local scales) play in modulating and forecasting aerosol pollution in Beijing and its surrounding area.

scholarly journals Classification of summertime synoptic patterns in Beijing and their associations with boundary layer structure affecting aerosol pollution

2017 ◽  
Vol 17 (4) ◽  
pp. 3097-3110 ◽  
Author(s):  
Yucong Miao ◽  
Jianping Guo ◽  
Shuhua Liu ◽  
Huan Liu ◽  
Zhanqing Li ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Air Quality ◽  
Large Scale ◽  
Layer Structure ◽  
Inversion Layer ◽  
Near Surface ◽  
Synoptic Patterns ◽  
Synoptic Conditions ◽  
Aerosol Pollution ◽  
Fine Resolution

Abstract. Meteorological conditions within the planetary boundary layer (PBL) are closely governed by large-scale synoptic patterns and play important roles in air quality by directly and indirectly affecting the emission, transport, formation, and deposition of air pollutants. Partly due to the lack of long-term fine-resolution observations of the PBL, the relationships between synoptic patterns, PBL structure, and aerosol pollution in Beijing have not been well understood. This study applied the obliquely rotated principal component analysis in T-mode to classify the summertime synoptic conditions over Beijing using the National Centers for Environmental Prediction reanalysis from 2011 to 2014, and investigated their relationships with PBL structure and aerosol pollution by combining numerical simulations, measurements of surface meteorological variables, fine-resolution soundings, the concentration of particles with diameters less than or equal to 2.5 µm, total cloud cover (CLD), and reanalysis data. Among the seven identified synoptic patterns, three types accounted for 67 % of the total number of cases studied and were associated with heavy aerosol pollution events. These particular synoptic patterns were characterized by high-pressure systems located to the east or southeast of Beijing at the 925 hPa level, which blocked the air flow seaward, and southerly PBL winds that brought in polluted air from the southern industrial zone. The horizontal transport of pollutants induced by the synoptic forcings may be the most important factor affecting the air quality of Beijing in summer. In the vertical dimension, these three synoptic patterns featured a relatively low boundary layer height (BLH) in the afternoon, accompanied by high CLD and southerly cold advection from the seas within the PBL. The high CLD reduced the solar radiation reaching the surface, and suppressed the thermal turbulence, leading to lower BLH. Besides, the numerical sensitive experiments show that cold advection induced by the large-scale synoptic forcing may have cooled the PBL, leading to an increase in near-surface stability and a decrease in the BLH in the afternoon. Moreover, when warm advection appeared simultaneously above the top level of the PBL, the thermal inversion layer capping the PBL may have been strengthened, resulting in the further suppression of PBL and thus the deterioration of aerosol pollution levels. This study has important implications for understanding the crucial roles that meteorological factors (at both synoptic and local scales) play in modulating and forecasting aerosol pollution in Beijing and its surrounding area.

scholarly journals Impact of atmospheric circulations on aerosol distributions in autumn over eastern China: observational evidence

2015 ◽  
Vol 15 (21) ◽  
pp. 12115-12138 ◽  
Author(s):  
X. Y. Zheng ◽  
Y. F. Fu ◽  
Y. J. Yang ◽  
G. S. Liu
Keyword(s):  
Large Scale ◽  
Eastern China ◽  
Lower Troposphere ◽  
Reanalysis Data ◽  
Circulation Type ◽  
Lower Atmosphere ◽  
Study Region ◽  
Middle Troposphere ◽  
Heavy Pollution ◽  
Pollution Events

Abstract. Regional heavy pollution events in eastern China (110–122° E, 28–40° N) are causing serious environmental problems. In this study, the relationship between the degree of regional pollution and the patterns of large-scale atmospheric circulation over eastern China in October is investigated using 10-year (2001–2010) Terra/MODIS aerosol optical depth and NCEP reanalysis data by both case study and composite analysis. Eighteen polluted and 10 clean episodes are selected and categorised into six polluted types and three clean types respectively. Generally speaking, weather patterns such as a uniform surface pressure field in eastern China or a steady straight westerly in the middle troposphere, particularly when being at the rear of the anticyclone at 850 hPa, are typically responsible for heavy pollution events. Meanwhile, clean episodes occur when strong southeastward cold air advection prevails below the middle troposphere or air masses are transported from sea to land. Uniform descending motion prevails over the study region, trapping pollutants in the lower atmosphere. Therefore, the value of vertical velocity averaged from 1000 to 100 hPa and divergence of wind field in the lower troposphere are used in this study to quantify the diffusion conditions in each circulation type. The results reveal that it is often a clean episode when both the mean downward motion (larger than 2.56 × 10−2 Pa s−1) and the divergence of low-level winds (larger than 1.79 × 10−2 s−1) are strong. Otherwise, it is more likely to be a polluted episode.

scholarly journals Differential hydrocarbon enrichment in deep Paleogene tight sandstones of the Dongpu Depression in Eastern China

2021 ◽  
pp. 014459872098811
Author(s):  
Yuanyuan Zhang ◽  
Zhanli Ren ◽  
Youlu Jiang ◽  
Jingdong Liu
Keyword(s):  
Natural Gas ◽  
Crude Oil ◽  
Large Scale ◽  
Eastern China ◽  
Continuous Distribution ◽  
Gas Reservoirs ◽  
Pyrolysis Gas ◽  
Hydrocarbon Charging ◽  
Dongpu Depression ◽  
Kerogen Pyrolysis

To clarify the characteristics and enrichment rules of Paleogene tight sandstone reservoirs inside the rifted-basin of Eastern China, the third member of Shahejie Formation (abbreviated as Es3) in Wendong area of Dongpu Depression is selected as the research object. It not only clarified the geochemical characteristics of oil and natural gas in the Es3 of Wendong area through testing and analysis of crude oil biomarkers, natural gas components and carbon isotopes, etc.; but also compared and explained the types and geneses of oil and gas reservoirs in slope zone and sub-sag zone by matching relationship between the porosity evolution of tight reservoirs and the charging process of hydrocarbons. Significant differences have been found between the properties and the enrichment rules of hydrocarbon reservoirs in different structural areas in Wendong area. The study shows that the Paleogene hydrocarbon resources are quasi-continuous distribution in Wendong area. The late kerogen pyrolysis gas, light crude oil, medium crude oil, oil-cracked gas and the early kerogen pyrolysis gas are distributed in a semicircle successively, from the center of sub-sag zone to the uplift belt, that is the result of two discontinuous hydrocarbon charging. Among them, the slope zone is dominated by early conventional filling of oil-gas mixture (at the late deposition period of Dongying Formation, about 31–27 Ma ago), while the reservoirs are gradually densified in the late stage without large-scale hydrocarbon charging (since the deposition stage of Minghuazhen Formation, about 6–0 Ma). In contrast, the sub-sag zone is lack of oil reservoirs, but a lot of late kerogen pyrolysis gas reservoirs are enriched, and the reservoir densification and hydrocarbon filling occur in both early and late stages.

scholarly journals Spatial and Temporal Characteristics of Environmental Air Quality and Its Relationship with Seasonal Climatic Conditions in Eastern China during 2015–2018

2021 ◽  
Vol 18 (9) ◽  
pp. 4524
Author(s):  
Zhiyuan Wang ◽  
Xiaoyi Shi ◽  
Chunhua Pan ◽  
Sisi Wang
Keyword(s):  
Particulate Matter ◽  
Air Quality ◽  
Air Pollutants ◽  
Large Scale ◽  
Asian Summer Monsoon ◽  
Eastern China ◽  
Climatic Conditions ◽  
Uniform Structure ◽  
Concentration Limit ◽  
Environmental Air

Exploring the relationship between environmental air quality (EAQ) and climatic conditions on a large scale can help better understand the main distribution characteristics and the mechanisms of EAQ in China, which is significant for the implementation of policies of joint prevention and control of regional air pollution. In this study, we used the concentrations of six conventional air pollutants, i.e., carbon monoxide (CO), sulfur dioxide (SO2), nitrogen dioxide (NO2), fine particulate matter (PM2.5), coarse particulate matter (PM10), and ozone (O3), derived from about 1300 monitoring sites in eastern China (EC) from January 2015 to December 2018. Exploiting the grading concentration limit (GB3095-2012) of various pollutants in China, we also calculated the monthly average air quality index (AQI) in EC. The results show that, generally, the EAQ has improved in all seasons in EC from 2015 to 2018. In particular, the concentrations of conventional air pollutants, such as CO, SO2, and NO2, have been decreasing year by year. However, the concentrations of particulate matter, such as PM2.5 and PM10, have changed little, and the O3 concentration increased from 2015 to 2018. Empirical mode decomposition (EOF) was used to analyze the major patterns of AQI in EC. The first mode (EOF1) was characterized by a uniform structure in AQI over EC. These phenomena are due to the precipitation variability associated with the East Asian summer monsoon (EASM), referred to as the “summer–winter” pattern. The second EOF mode (EOF2) showed that the AQI over EC is a north–south dipole pattern, which is bound by the Qinling Mountains and Huaihe River (about 35° N). The EOF2 is mainly caused by seasonal variations of the mixed concentration of PM2.5 and O3. Associated with EOF2, the Mongolia–Siberian High influences the AQI variation over northern EC by dominating the low-level winds (10 m and 850 hPa) in autumn and winter, and precipitation affects the AQI variation over southern EC in spring and summer.

scholarly journals Transformer Meets Convolution: A Bilateral Awareness Network for Semantic Segmentation of Very Fine Resolution Urban Scene Images

2021 ◽  
Vol 13 (16) ◽  
pp. 3065
Author(s):  
Libo Wang ◽  
Rui Li ◽  
Dongzhi Wang ◽  
Chenxi Duan ◽  
Teng Wang ◽  
...  
Keyword(s):  
Large Scale ◽  
Texture Features ◽  
Semantic Segmentation ◽  
Autonomous Driving ◽  
Research Field ◽  
Learning Approaches ◽  
Fine Grained ◽  
Urban Scene ◽  
Fine Resolution ◽  
With Memory

Semantic segmentation from very fine resolution (VFR) urban scene images plays a significant role in several application scenarios including autonomous driving, land cover classification, urban planning, etc. However, the tremendous details contained in the VFR image, especially the considerable variations in scale and appearance of objects, severely limit the potential of the existing deep learning approaches. Addressing such issues represents a promising research field in the remote sensing community, which paves the way for scene-level landscape pattern analysis and decision making. In this paper, we propose a Bilateral Awareness Network which contains a dependency path and a texture path to fully capture the long-range relationships and fine-grained details in VFR images. Specifically, the dependency path is conducted based on the ResT, a novel Transformer backbone with memory-efficient multi-head self-attention, while the texture path is built on the stacked convolution operation. In addition, using the linear attention mechanism, a feature aggregation module is designed to effectively fuse the dependency features and texture features. Extensive experiments conducted on the three large-scale urban scene image segmentation datasets, i.e., ISPRS Vaihingen dataset, ISPRS Potsdam dataset, and UAVid dataset, demonstrate the effectiveness of our BANet. Specifically, a 64.6% mIoU is achieved on the UAVid dataset.

Dynamic and Thermodynamic Relations of Distinctive Stratus Clouds on the Lee Side of the Tibetan Plateau in the Cold Season

2013 ◽  
Vol 26 (21) ◽  
pp. 8378-8391 ◽  
Author(s):  
Yi Zhang ◽  
Rucong Yu ◽  
Jian Li ◽  
Weihua Yuan ◽  
Minghua Zhang
Keyword(s):  
Tibetan Plateau ◽  
Large Scale ◽  
Eastern China ◽  
Cold Season ◽  
Water Vapor Transport ◽  
The Tibetan Plateau ◽  
Primary Role ◽  
Moist Air ◽  
Low Level ◽  
Stratus Clouds

Abstract Given the large discrepancies that exist in climate models for shortwave cloud forcing over eastern China (EC), the dynamic (vertical motion and horizontal circulation) and thermodynamic (stability) relations of stratus clouds and the associated cloud radiative forcing in the cold season are examined. Unlike the stratus clouds over the southeastern Pacific Ocean (as a representative of marine boundary stratus), where thermodynamic forcing plays a primary role, the stratus clouds over EC are affected by both dynamic and thermodynamic factors. The Tibetan Plateau (TP)-forced low-level large-scale lifting and high stability over EC favor the accumulation of abundant saturated moist air, which contributes to the formation of stratus clouds. The TP slows down the westerly overflow through a frictional effect, resulting in midlevel divergence, and forces the low-level surrounding flows, resulting in convergence. Both midlevel divergence and low-level convergence sustain a rising motion and vertical water vapor transport over EC. The surface cold air is advected from the Siberian high by the surrounding northerly flow, causing low-level cooling. The cooling effect is enhanced by the blocking of the YunGui Plateau. The southwesterly wind carrying warm, moist air from the east Bay of Bengal is uplifted by the HengDuan Mountains via topographical forcing; the midtropospheric westerly flow further advects the warm air downstream of the TP, moistening and warming the middle troposphere on the lee side of the TP. The low-level cooling and midlevel warming together increase the stability. The favorable dynamic and thermodynamic large-scale environment allows for the formation of stratus clouds over EC during the cold season.

The Two-Party System in British Politics

1953 ◽  
Vol 47 (2) ◽  
pp. 337-358 ◽  
Author(s):  
Leslie Lipson
Keyword(s):  
Economic Policy ◽  
Party System ◽  
Large Scale ◽  
British Politics ◽  
State Planning ◽  
Party Government ◽  
Contemporary State ◽  
Long Duration ◽  
Effective System ◽  
Laissez Faire

Britain may fairly be called the classic home of two-party government. This claim is justifiable because of some characteristics for which the system, as employed in Britain, is distinctive. Chief among these is its long duration. Although there is room for disagreement among historians about the time and circumstances of its birth, it would be difficult to deny that two-party government was established earlier, has lasted longer, and at the present time is probably more firmly rooted there than in any contemporary state. Indeed, the practice of simplifying the complexities of politics into a contest for office between a pair of major claimants has endured in Britain through a catalogue of changes which would assuredly have wrecked a less effective system. In that country it has survived the evolution from an oligarchy of aristocrats to a democracy of the whole people; the transfer of power from monarchy to parliament and then from parliament to cabinet; the rise of large-scale industry with its social aftermath; the switch in economic policy from mercantilism to laissez faire and from this to state planning; and withal, the expansion and subsequent shrinkage of Britain's international might.

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