scholarly journals Regional severe particle pollution and its association with synoptic weather patterns in the Yangtze River Delta region, China

2017 ◽  
Author(s):  
Lei Shu ◽  
Min Xie ◽  
Da Gao ◽  
Tijian Wang ◽  
Dexian Fang ◽  
...  
Keyword(s):  
Yangtze River ◽  
East Asian ◽  
Yangtze River Delta ◽  
Air Masses ◽  
East Asian Trough ◽  
Weather Patterns ◽  
Synoptic Weather ◽  
Particle Pollution ◽  
Pm2.5 And Pm10 ◽  
The Yangtze River Delta

Abstract. Regional air pollution is significantly associated with the dominant weather systems. In this study, the relationship between the particle pollution over the Yangtze River Delta (YRD) region and the weather patterns is investigated. Firstly, the pollution characteristics of particles (PM2.5 and PM10) in YRD are studied by using the in situ monitoring data in 16 cities from December 2013 to November 2014. The results show that the annual average concentrations in the cities of Jiangsu Province all exceed the national air quality standard. The pollution level is higher in the inland areas. Highest values can be found in Nanjing, with the concentrations of PM2.5 and PM10 being 79 μg · m−3 and 130  μg · m−3, respectively. The PM2.5/PM10 ratios are usually high in YRD, indicating that PM2.5 is the overwhelmingly dominant particle pollutant. The wintertime peak of particle concentrations is tightly linked to the increased emissions in the heating season and the poor meteorological condition. Secondly, based on NCEP reanalysis data, synoptic weather classification is conducted to reveal that the weather patterns are easy to cause heavy pollution in YRD. Five typical synoptic patterns are objectively identified, including the East Asian trough rear pattern, the depression inverted trough pattern, the transversal trough pattern, the high-pressure controlled pattern, and the northeast cold vortex pattern. Finally, synthetic analysis of meteorological fields and backward trajectory calculation are used to further clarify how these patterns impact particle concentrations. It is clarified that YRD is largely influenced by polluted air masses from the northern and the southern inland areas when it is at the rear of the East Asian major trough. In this case, the strong northwest wind hinders the vertical outward transport of pollutants. Thus, the East Asian trough rear pattern is quite favorable for the accumulation of pollutants in YRD, and respectively contributes 70.4 % and 78.3 % to the occurrence of large-scale regional PM2.5 and PM10 pollution episodes. While under the weather systems for other patterns, the clean marine air masses may play great roles in the mitigation of particle pollution in YRD. The correlation between weather patterns and particle pollution can provide valuable views in the decision-making on pollution control and mitigation strategies.

scholarly journals Regional severe particle pollution and its association with synoptic weather patterns in the Yangtze River Delta region, China

2017 ◽  
Vol 17 (21) ◽  
pp. 12871-12891 ◽  
Author(s):  
Lei Shu ◽  
Min Xie ◽  
Da Gao ◽  
Tijian Wang ◽  
Dexian Fang ◽  
...  
Keyword(s):  
Yangtze River Delta ◽  
Mean Value ◽  
Air Masses ◽  
Weather Patterns ◽  
Synoptic Weather ◽  
Particle Pollution ◽  
Pm2.5 And Pm10 ◽  
Marine Air ◽  
The Yrd ◽  
The Yangtze River Delta

Abstract. Regional air pollution is significantly associated with dominant weather systems. In this study, the relationship between the particle pollution over the Yangtze River Delta (YRD) region and weather patterns is investigated. First, the pollution characteristics of particles in the YRD are studied using in situ monitoring data (PM2.5 and PM10) in 16 cities and Terra/MODIS AOD (aerosol optical depth) products collected from December 2013 to November 2014. The results show that the regional mean value of AOD is high in the YRD, with an annual mean value of 0.71±0.57. The annual mean particle concentrations in the cities of Jiangsu Province all exceed the national air quality standard. The pollution level is higher in inland areas, and the highest concentrations of PM2.5 and PM10 are 79 and 130 µg m−3, respectively, in Nanjing. The PM2.5  :  PM10 ratios are typically high, thus indicating that PM2.5 is the overwhelmingly dominant particle pollutant in the YRD. The wintertime peak of particle concentrations is tightly linked to the increased emissions during the heating season as well as adverse meteorological conditions. Second, based on NCEP (National Center for Environmental Prediction) reanalysis data, synoptic weather classification is conducted and five typical synoptic patterns are objectively identified. Finally, the synthetic analysis of meteorological fields and backward trajectories are applied to further clarify how these patterns impact particle concentrations. It is demonstrated that air pollution is more or less influenced by high-pressure systems. The relative position of the YRD to the anti-cyclonic circulation exerts significant effects on the air quality of the YRD. The YRD is largely influenced by polluted air masses from the northern and the southern inland areas when it is located at the rear of the East Asian major trough. The significant downward motion of air masses results in stable weather conditions, thereby hindering the diffusion of air pollutants. Thus, this pattern is quite favorable for the accumulation of pollutants in the YRD, resulting in higher regional mean PM10 (116.5 ± 66.9 µg m−3), PM2.5 (75.9 ± 49.9 µg m−3), and AOD (0.74) values. Moreover, this pattern is also responsible for the occurrence of most large-scale regional PM2.5 (70.4 %) and PM10 (78.3 %) pollution episodes. High wind speed and clean marine air masses may also play important roles in the mitigation of pollution in the YRD. Especially when the clean marine air masses account for a large proportion of all trajectories (i.e., when the YRD is affected by the cyclonic system or oceanic circulation), the air in the YRD has a lesser chance of being polluted. The observed correlation between weather patterns and particle pollution can provide valuable insight into making decisions about pollution control and mitigation strategies.

scholarly journals East Asian monsoon during the past 10,000 years recorded by grain size of Yangtze River delta

2021 ◽  
Vol 13 (1) ◽  
pp. 505-516
Author(s):  
Xiaohui Wang ◽  
Longsheng Wang ◽  
Shouyun Hu ◽  
Ge Yu ◽  
Qing Wang ◽  
...  
Keyword(s):  
Grain Size ◽  
Yangtze River ◽  
Asian Monsoon ◽  
Environmental Changes ◽  
East Asian Monsoon ◽  
East Asian ◽  
Yangtze River Delta ◽  
River Delta ◽  
The Yangtze River ◽  
The Yangtze River Delta

Abstract Paleoenvironmental research is critical for understanding delta evolution processes and managing delta sustainability, particularly for delta experiencing significant recent fluvial sediment discharge. Based on other previously reported optically stimulated luminescence (OSL) data, Holocene environmental changes of the Yangtze River delta in response to climate fluctuations and human activities were reviewed on the basis of grain-size analyses of core YZ07. The results of grain-size and end-member analysis (EMA) provide a detailed history of East Asian monsoon variability and environmental changes since ∼10,000 cal year B.P. The lower median values (Md) and sand content reflect relatively cool and dry climate conditions between 10,000 and 9,570 cal year B.P. During the early Holocene (9,570–7,630 cal year B.P.), the highest Md values and sand contents and the lowest end member 2 (EM2) contents suggest the Holocene transgression. The increased Md values and sand contents indicate that the climate conditions were warm and wet during the mid-Holocene thermal optimum. From 4,690 to 4,150 cal year B.P., the climate was cool and dry, corresponding to the cool event, as indicated by the finer grain size. Subsequently, between 4,150 and 2,850 cal year B.P., the grain size derived from the Md value and sand content increased, which reflect a wet and warm episode. The climate, which shifted from warm and wet to cool and dry between 2,850 and 1,020 cal year B.P., may have caused a reduction in the sand contents and Md values. After 1,020 cal year B.P., the lowest values of Md and Standard deviation (Sd) and the highest contents of EM2 and clay suggest that the Yangtze River delta has been severely affected by anthropogenic activity. The variability of the East Asian monsoon intensity in the Yangtze River delta strongly correlates with other East Asian monsoon paleoclimate records in China. These results are important for investigations into the interactions between regional systems and global change in monsoonal climatic regions and can provide an example of the evolution of a large scale geomorphic feature resulting from river-sea interaction.

scholarly journals Ozone variability induced by synoptic weather patterns in warm seasons of 2014–2018 over the Yangtze River Delta region, China

2021 ◽  
Vol 21 (8) ◽  
pp. 5847-5864
Author(s):  
Da Gao ◽  
Min Xie ◽  
Jane Liu ◽  
Tijian Wang ◽  
Chaoqun Ma ◽  
...  
Keyword(s):  
Time Series ◽  
North China ◽  
Meteorological Factors ◽  
Yangtze River Delta ◽  
Aleutian Low ◽  
Weather Patterns ◽  
The North ◽  
Synoptic Weather ◽  
The Yrd ◽  
The Yangtze River Delta

Abstract. Ozone (O3) pollution is of great concern in the Yangtze River Delta (YRD) region of China, and the regional O3 pollution is closely associated with dominant weather systems. With a focus on the warm seasons (April–September) from 2014 to 2018, we quantitatively analyze the characteristics of O3 variations over the YRD, the impacts of large-scale and synoptic-scale circulations on the O3 variations and the associated meteorological controlling factors, based on observed ground-level O3 and meteorological data. Our analysis suggests an increasing trend of the regional mean O3 concentration in the YRD at 1.8 ppb per year over 2014–2018. Spatially, the empirical orthogonal function analysis suggests the dominant mode accounting for 65.7 % variation in O3, implying that an increase in O3 is the dominant tendency in the entire YRD region. Meteorology is estimated to increase the regional mean O3 concentration by 3.1 ppb at most from 2014 to 2018. In particular, relative humidity (RH) plays the most important role in modulating the inter-annual O3 variation, followed by solar radiation (SR) and low cloud cover (LCC). As atmospheric circulations can affect local meteorological factors and O3 levels, we identify five dominant synoptic weather patterns (SWPs) in the warm seasons in the YRD using the t-mode principal component analysis classification. The typical weather systems of SWPs include the western Pacific Subtropical High (WPSH) under SWP1, a continental high and the Aleutian low under SWP2, an extratropical cyclone under SWP3, a southern low pressure and WPSH under SWP4 and the north China anticyclone under SWP5. The variations of the five SWPs are all favorable to the increase in O3 concentrations over 2014–2018. However, crucial meteorological factors leading to increases in O3 concentrations are different under different SWPs. These factors are identified as significant decreases in RH and increases in SR under SWP1, 4 and 5, significant decreases in RH, increases in SR and air temperature (T2) under SWP2 and significant decreases in RH under SWP3. Under SWP1, 4 and 5, significant decreases in RH and increases in SR are predominantly caused by the WPSH weakening under SWP1, the southern low pressure weakening under SWP4 and the north China anticyclone weakening under SWP5. Under SWP2, significant decreases in RH, increases in SR and T2 are mainly produced by the Aleutian low extending southward and a continental high weakening. Under SWP3, significant decreases in RH are mainly induced by an extratropical cyclone strengthening. These changes in atmospheric circulations prevent the water vapor in the southern and northern sea from being transported to the YRD and result in RH significantly decreasing under each SWP. In addition, strengthened descending motions (behind the strengthening trough and in front of the strengthening ridge) lead to decreases in LCC and significant increases in SR under SWP1, 2, 4 and 5. The significant increases in T2 would be due to weakening cold flow introduced by a weakening continental high. Most importantly, the changes in the SWP intensity can make large variations in meteorological factors and contribute more to the O3 inter-annual variation than the changes in the SWP frequency. Finally, we reconstruct an empirical orthogonal function (EOF) mode 1 time series that is highly correlated with the original O3 time series, and the reconstructed time series performs well in defining the change in SWP intensity according to the unique feature under each of the SWPs.

scholarly journals Characterization and Source Apportionment of Fine Particles during a Heavy Pollution Episode over the Yangtze River Delta, China

Atmosphere ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 720
Author(s):  
Li Xia ◽  
Bin Zhu ◽  
Honglei Wang ◽  
Hanqing Kang ◽  
Junlin An
Keyword(s):  
Yangtze River ◽  
Fine Particles ◽  
Yangtze River Delta ◽  
River Delta ◽  
Chemical Components ◽  
The Yangtze River ◽  
Air Masses ◽  
Regional Background ◽  
The Yangtze River Delta ◽  
Rainy Days

Regional-scale field observations of fine particles (PM2.5) were carried out at urban, suburban and regional background sites across the Yangtze River Delta (YRD) from 15–30 January 2015. The coefficients of divergence (CD) values reveal the similarity of dataset at the three sites. The PM2.5 concentrations and meteorological data exhibit temporal synchronization. From January 15 to 26, the YRD experienced severe PM2.5 pollution resulting from a cold front moving through and high-pressure control. Then, a 4-day intermittent rain event from 27–30 January significantly scavenged PM2.5. For the chemical components in PM2.5, secondary inorganic ions were dominant, and they accounted for larger proportions at the urban and suburban sites than at the regional background site. The OC/EC ratios were higher in daytime than at night, and were lower on polluted days than on clean (rainy) days. The principal sources of PM2.5 were secondary nitrate (38%) and sulfate (23%) formation, biomass burning (14%), and marine source (8%). Marine (16%) and sulfate (30%) sources were enhanced on clean (rainy) days, indicating the notable effect of marine air masses on PM2.5 chemical components. The open burning source contribution at the regional site was the largest during the polluted period because more air masses arrived from combustion zones.

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