scholarly journals Latitudinal gradient and interannual variation of PM<sub>10</sub> concentration over eighty-six Chinese cities

2009 ◽  
Vol 9 (6) ◽  
pp. 23141-23185 ◽  
Author(s):  
W. J. Qu ◽  
R. Arimoto ◽  
X. Y. Zhang ◽  
Y. Q. Wang ◽  
L. F. Sheng ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Latitudinal Gradient ◽  
Eastern China ◽  
Pollution Index ◽  
Northern China ◽  
Pm10 Concentration ◽  
Middle Zone ◽  
Chinese Cities ◽  
Southern Zone ◽  
Northern Cities

Abstract. The spatial distribution of the aerosols over 86 major Chinese cities was constructed from 137 845 daily averaged PM10 (particles with diameter ≤10 μm) concentrations calculated from air pollution index (API) records spanning from summer 2000 to winter 2006. This dataset was based on days when PM10 was categorized as the principal pollutant, accounting for 91.6% of the total recorded days. The 83 cities in mid-eastern China (longitude 100° E to 130° E) were separated into three latitudinal zones with the Qinlin Mountain – the Huaihe River and the Yunnan-Guizhou Plateau – the Jiangnan Hill – the Wuyi Mountain as the boundaries. The spatial distribution of PM10 was complicated; the high-value spots in northern China (concentration ranged from 127.1 to 192.1 μg m−3) included Urumchi, Lanzhou-Xining, Weinan-Xi'an, Taiyuan-Datong-Yangquan-Changzhi, Pingdingshan-Kaifeng, Beijing-Tianjin-Shijiazhuang, Jinan, and Shenyang-Anshan-Fushun; in the middle zone, the high PM10 spots (concentration within 119.1–146.6 μg m−3) were Chongqing-Chengdu-Luzhou, Changsha-Wuhan, and Nanjing-Hangzhou; while in the southern zone, four cities (Qujing, Guiyang, Guangzhou and Shaoguan) showed higher PM10 concentration (>80 μg m−3). An overall latitudinal gradient was distinct; the median PM10 concentrations decreased from 108 μg m−3 for the 38 northern cities to 95 μg m−3 and 55 μg m−3 for the middle (26 cities) and southern (19 cities) zones, respectively. Linear regression between PM10 concentration and latitude of the cities also confirmed this gradient. PM10 concentration and the APIs exhibited similar seasonality with wintertime maxima and summertime minima, and the second highest values in spring. PM10 level showed a decreasing trend (−23.2 μg m−3) for the northern cities during 2000 to 2006. For the other two zones, the PM10 levels fluctuated, but showed unobvious change (−1.7 μg m−3) for the middle zone and increased slightly (+6.2 μg m−3) for the southern zone during the course.

scholarly journals Spatial distribution and interannual variation of surface PM<sub>10</sub> concentrations over eighty-six Chinese cities

2010 ◽  
Vol 10 (12) ◽  
pp. 5641-5662 ◽  
Author(s):  
W. J. Qu ◽  
R. Arimoto ◽  
X. Y. Zhang ◽  
C. H. Zhao ◽  
Y. Q. Wang ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Eastern China ◽  
Pollution Index ◽  
Northern China ◽  
Pm10 Concentration ◽  
Natural Landscape ◽  
Chinese Cities ◽  
Northern Cities ◽  
Pm10 Level ◽  
The Relationship

Abstract. The spatial distribution of the aerosols over 86 Chinese cities was reconstructed from air pollution index (API) records for summer 2000 to winter 2006. PM10 (particulate matter ≤10 μm) mass concentrations were calculated for days when PM10 was the principal pollutant, these accounted for 91.6% of the total 150 428 recorded days. The 83 cities in mid-eastern China (100° E to 130° E) were separated into three latitudinal zones using natural landscape features as boundaries. Areas with high PM10 level in northern China (127 to 192 μg m−3) included Urumchi, Lanzhou-Xining, Weinan-Xi'an, Taiyuan-Datong-Yangquan-Changzhi, Pingdingshan-Kaifeng, Beijing-Tianjin-Shijiazhuang, Jinan, and Shenyang-Anshan-Fushun; in the middle zone, high PM10 (119–147 μg m−3) occurred at Chongqing-Chengdu-Luzhou, Changsha-Wuhan, and Nanjing-Hangzhou; in the southern zone, only four cities (Qujing, Guiyang, Guangzhou and Shaoguan) showed PM10 concentration >80 μg m−3. The median PM10 concentration decreased from 108 μg m−3 for the northern cities to 95 μg m−3 and 55 μg m−3 for the middle and southern zones, respectively. PM10 concentration and the APIs both exhibited wintertime maxima, summertime minima, and the second highest values in spring. PM10showed evidence for a decreasing trend for the northern cities while in the other zones urban PM10 levels fluctuated, but showed no obvious change over time. The spatial distribution of PM10 was compared with the emissions, and the relationship between the surface PM10 concentration and the aerosol optical depth (AOD) was also discussed.

scholarly journals A Climatology and Extreme Value Analysis of Large Hail in China

2020 ◽  
Vol 148 (4) ◽  
pp. 1431-1447
Author(s):  
Xiang Ni ◽  
Andreas Muehlbauer ◽  
John T. Allen ◽  
Qinghong Zhang ◽  
Jiwen Fan
Keyword(s):  
Spatial Distribution ◽  
Return Period ◽  
Eastern China ◽  
Northern China ◽  
Extreme Value ◽  
Western China ◽  
Extreme Value Analysis ◽  
Annual Maximum ◽  
Return Periods ◽  
Value Analysis

Abstract Hail size records are analyzed at 2254 stations in China and a hail size climatology is developed based on gridded hail observations for the period 1960–2015. It is found that the annual percentiles of hail size records changed sharply and national-wide after 1980, therefore two periods, 1960–79 and 1980–2015, are studied. There are some similarities between the two periods in terms of the characteristics of hail size such as the spatial distribution patterns of mean annual maximum hail size and occurrence week of annual maximum hail size. The 1980–2015 period had higher observation density than the 1960–79 period, but showed smaller mean annual maximum hail size, especially in northern China. In the majority of grid boxes, the annual maximum hail size experienced a decreasing trend during the 1980–2015 period. A Gumbel extreme value model is fitted to each grid box to estimate the return periods of maximum hail size. The scale and location parameter of the fitted Gumbel distributions are higher in eastern China than in western China, thereby reflecting a greater likelihood of large hail in eastern China. In southern China, the maximum hail size exceeds 127 mm for a 10-yr return period, whereas in northern China maximum hail size exceeds this threshold for a 50-yr return period. The Gumbel model is found to potentially underestimate the maximum hail size for certain return periods, but provides a more informed picture of the spatial distribution of extreme hail size and the regional differences.

scholarly journals Impacts of East Asian Summer and Winter Monsoon on Interannual Variations of Mass Concentrations and Direct Radiative Forcing of Black Carbon over Eastern China

2016 ◽  
Author(s):  
Yu Hao Mao ◽  
Hong Liao
Keyword(s):  
Black Carbon ◽  
Radiative Forcing ◽  
Southern China ◽  
East Asian ◽  
Eastern China ◽  
Northern China ◽  
Winter Monsoon ◽  
Interannual Variations ◽  
Direct Radiative Forcing ◽  
Asian Summer

Abstract. We applied a global three-dimensional chemical transport model (GEOS-Chem) to examine the impacts of the East Asian monsoon on the interannual variations of mass concentrations and direct radiative forcing (DRF) of black carbon (BC) over eastern China (110–125° E, 20–45° N). With emissions fixed at the year 2010 levels, model simulations were driven by the Goddard Earth Observing System (GEOS-4) meteorological fields for 1986–2006 and the Modern Era Retrospective-analysis for Research and Applications (MERRA) meteorological fields for 1980–2010. During the period of 1986–2006, simulated JJA and DJF surface BC concentrations were higher in MERRA than in GEOS-4 by 0.30 µg m−3 (44 %) and 0.77 µg m−3 (54 %), respectively, because of the generally weaker precipitation in MERRA. We found that the strength of the East Asian summer monsoon (EASM, (East Asian winter monsoon, EAWM)) negatively correlated with simulated JJA (DJF) surface BC concentrations (r = –0.7 (–0.7) in GEOS-4 and –0.4 (–0.7) in MERRA), mainly by the changes in atmospheric circulation. Relative to the five strongest EASM years, simulated JJA surface BC concentrations in the five weakest monsoon years were higher over northern China (110–125° E, 28–45° N) by 0.04–0.09 µg m−3 (3–11 %), but lower over southern China (110–125° E, 20–27° N) by 0.03–0.04 µg m−3 (10–11 %). Compared to the five strongest EAWM years, simulated DJF surface BC concentrations in the five weakest monsoon years were higher by 0.13–0.15 µg m−3 (5–8 %) in northern China and by 0.04–0.10 µg m−3 (3–12 %) in southern China. The resulting JJA (DJF) mean all-sky DRF of BC at the top of the atmosphere were 0.04 W m−2 (3 %, (0.03 W m−2, 2 %)) higher in northern China but 0.06 W m−2 (14 %, (0.03 W m−2, 3 %)) lower in southern China. In the weakest monsoon years, the weaker vertical convection led to the lower BC concentrations above 1–2 km in southern China, and therefore the lower BC DRF in the region. The differences in vertical profiles of BC between the weakest and strongest EASM years (1998–1997) and EAWM years (1990–1996) reached up to –0.09 µg m−3 (–46 %) and –0.08 µg m−3 (–11 %) at 1–2 km in eastern China.

scholarly journals Characteristics and factors influencing the natural regeneration of Larix principis-rupprechtii seedlings in northern China

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e12327
Author(s):  
Weiwen Zhao ◽  
Wenjun Liang ◽  
Youzhi Han ◽  
Xi Wei
Keyword(s):  
Spatial Distribution ◽  
Natural Regeneration ◽  
Pair Correlation ◽  
Principal Component ◽  
Northern China ◽  
Point Pattern Analysis ◽  
Point Pattern ◽  
Adult Trees ◽  
Herb Diversity ◽  
Univariate Distribution

Larix principis-rupprechtii is an important and widely distributed species in the mountains of northern China. However, it has inefficient natural regeneration in many stands and difficulty recruiting seedlings and saplings. In this study, we selected six plots with improved naturally-regenerated L. principis-rupprechtii seedlings. A point pattern analysis (pair-correlation function) was applied to identify the spatial distribution pattern and correlation between adult trees and regenerated seedlings mapped through X/Y coordinates. Several possible influencing factors of L. principis-rupprechtii seedlings’ natural regeneration were also investigated. The results showed that the spatial distribution patterns of Larix principis-rupprechtii seedlings were concentrated 0–5 m around adult trees when considering the main univariate distribution type of regeneration. There was a positive correlation at a scale of 1.5–4 m between seedlings and adult trees according to bivariate analyses. When the scale was increased, these relationships were no longer significant. Generally, adult trees raised regenerated L. principis-rupprechtii seedlings at a scale of 1.5–4 m. Principal component analysis showed that the understory herb diversity and litter layer had a negative correlation with the number of regenerated seedlings. There was also a weak relationship between regenerated numbers and canopy density. This study demonstrated that the main factors promoting natural regeneration were litter thickness, herb diversity, and the distance between adult trees and regenerated seedlings. Additionally, these findings will provide a basis for the late-stage and practical management of natural regeneration in northern China’s mountain ranges.

scholarly journals Impacts of spatial mismatch on commuting time of urban residents in China

2014 ◽  
Vol 26 (3) ◽  
pp. 227-233 ◽  
Author(s):  
Danwen Bao ◽  
Tangyi Guo ◽  
Hongshan Xia
Keyword(s):  
Spatial Distribution ◽  
Spatial Patterns ◽  
Measurement Methods ◽  
Urban Residents ◽  
Spatial Mismatch ◽  
Chinese Cities ◽  
Job Accessibility ◽  
Nanjing City ◽  
Commuting Time ◽  
Job Opportunity

In much of studies on spatial mismatch between residential and employer locations, job accessibility has been measured. However, the apparent disadvantages of the traditional measurement methods on the studies of Chinese cities have been noted.  This paper proposed an optimized method for job accessibility measurement by introducing the weigh coefficient of job opportunity, which quantifies the degree of uneven distribution of job opportunity in the Chinese cities. Take Nanjing city for example, this new method was used to measure the spatial distribution of job opportunity, investigate the spatial patterns and analyze the influences of job accessibility on commuting behavior. The results show that the distribution of job accessibility in Nanjing exhibits the different spatial patterns and mechanisms compared with US cases.

scholarly journals What is the Price of Tea in China? Goods Prices and Availability in Chinese Cities

2020 ◽  
Vol 130 (632) ◽  
pp. 2438-2467
Author(s):  
Robert C Feenstra ◽  
Mingzhi Xu ◽  
Alexis Antoniades
Keyword(s):  
United States ◽  
Spatial Distribution ◽  
Consumer Goods ◽  
The United States ◽  
City Size ◽  
Competitive Effect ◽  
Chinese Cities ◽  
Price Indexes

Abstract We examine the price and variety of a sample of consumer goods at the barcode level in cities within China. Unlike the position in the United States, in China the prices of goods tend to be lower in larger cities. We explain that difference between the countries by the more uneven spatial distribution of manufacturers’ sales and retailers in China, and we confirm the pro-competitive effect of city size on reducing markups there. In both countries, there is a greater variety of goods in larger cities, but that effect is more pronounced in China. Combining the lower prices and greater variety, the price indexes in China for the goods we study fall with city size by around seven times more than in the United States.

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