In recent years, haze pollution events in Beijing have increased sharply, and the haze pollution of Beijing in October 2016 reached a new high. Meteorological conditions are thought to have influences on the haze occu...In recent years, haze pollution events in Beijing have increased sharply, and the haze pollution of Beijing in October 2016 reached a new high. Meteorological conditions are thought to have influences on the haze occurrence, yet the associated atmospheric circulation of haze in October and why the most severe haze pollution occurred in 2016 is still unclear. Here, the authors show through daily observation and reanalysis data that key regions of North Atlantic and North Pacific sea surface temperature （SST） anomalies may be the main factors for this most severe haze event. Since 2013, the SSTs of these two key regions have increased dramatically and reached a peak, which could have induced the severe haze pollution by affecting the Eurasia teleconnection （EU） and the North Pacific Oscillation, with these factors then providing favorable dynamic and thermodynamic conditions for haze development.展开更多
Satellite remote sensing is very important to obtain a variety of cloud properties. However, the data quality from satellites varies with different satellite characteristics. From December 2015 to January 2016, ground...Satellite remote sensing is very important to obtain a variety of cloud properties. However, the data quality from satellites varies with different satellite characteristics. From December 2015 to January 2016, ground-based air quality index （AQI） data showed severe haze events occurred successively in eastern China, particularly in the Beijing-Tianjin-Hebei region. During those days, a red alert （the most serious level）, orange alert （the second-highest level）, and yellow alert （the third-highest level） for haze, were issued in Beijing. Cloud detection from four sensors onboard the ＇A-Train＇satellite constellation were compared for two severe haze episodes, on 21 and 30 December 2015 respectively. Results showed that the MODIS sensor onboard the Aqua satellite misclassified aerosol as cloud, while the other three sensors-AIRS onboard Aqua, the cloud profiling radar onboard CloudSat, and CALIOP onboard CALIPSO-did not observe cloud over the same location. Through the high-AQI haze region in the CALIPSO and CloudSat orbit track, MODIS marked cloud close to the surface, while the MODIS true-color image and CALIOP observed an aerosol layer over the same location, suggesting MODIS falsely observed cloud there. Over the haze region in eastern China, MODIS observed 36% on average greater cloud fraction than AIRS, suggesting haze pollution induces a greater MODIS cloud amount.展开更多
Beijing experienced serious haze pollution from 24 November 2015 to 2 December 2015.To investigate the planetary boundary layer characteristics,especially turbulence characteristics,the authors analyzed the wind,tempe...Beijing experienced serious haze pollution from 24 November 2015 to 2 December 2015.To investigate the planetary boundary layer characteristics,especially turbulence characteristics,the authors analyzed the wind,temperature,humidity,and turbulence characteristics during heavily polluted weather by using the observational data of the 325-m meteorological tower in Beijing.The results indicate that the pollution was mainly caused by the easterly and southerly winds.There were negative correlations between wind speed,turbulent kinetic energy,friction velocity,and the PM2.5 concentration.During clean days,the wind speed greatly enhanced with height;however,during the period of heavy pollution,the wind speed changed a little from the nearsurface layer to the top of the tower.In contrast,the spatial variability of TKE from the nearsurface layer to the upper layer was not so obvious.The heavy haze pollution in this study was often characterized by the emergence of an inversion layer;therefore,the diurnal variation of the boundary layer temperature was very small.At the time of serious pollution,the relative humidity was near 100%.The diurnal variations of sensible heat flux and water vapor flux were significantly reduced when severe pollution occurred.展开更多
The characters of foggy day, misty day and hazy day were analyzed based on information in 7 meteorological stations in Xi’an during 1960 -2012. The results showed that during 1960-2012 in Xi’an, foggy day occurs mos...The characters of foggy day, misty day and hazy day were analyzed based on information in 7 meteorological stations in Xi’an during 1960 -2012. The results showed that during 1960-2012 in Xi’an, foggy day occurs most in mountainous regions and few in plains; misty day occurs most in cities and few in suburbs; hazy day occurs most in cities, followed by inner and outer suburbs. Annual foggy day in Xi’an changed from increasing to decreasing; misty day was increasing by 9.0 d/10 a; hazy day was decreasing by -7.7 d/10 a. During the 53 y in Xi’an, foggy day was shown in a singly-valley shape, and the minimum appeared in summer and the maximum appeared in winter; misty day was shown in a ＂V＂-shape, and the minimum （7.6 d） appeared in June and the maximum （3.8 d） in December; hazy day was shown in a ＂U＂-shape from May to September and the maximum in January （6.1）.展开更多
The simulated nitrogen deposition [control check （CBQ, 0 kg＇hm^2 /a; low nitrogen （LN）, 25 kg-hm^2 /a; medium nitrogen （MN）, 50 kg-hm^2/a high nitrogen （HN）, 150 kg·hm^2 /a] was performed from July 2014 ...The simulated nitrogen deposition [control check （CBQ, 0 kg＇hm^2 /a; low nitrogen （LN）, 25 kg-hm^2 /a; medium nitrogen （MN）, 50 kg-hm^2/a high nitrogen （HN）, 150 kg·hm^2 /a] was performed from July 2014 to August 2015 in the fotest-gtassland boundary in Zhuqudeng Village, Bujiu Township, Iinzhi City, Tibet Autonomous Regioii to analyze the activity of enzymes （invertase, catalase, ufease, amylase, cellukse, polyphenol oxidase, and p-glucosidase） in soil layers of 0-20 cm and 20-40 cm and explore die effect of different levels of nitrogen deposition on enzyme activity different layers of soiL The results showed tiiat＇ ① different levels of simulated nitrogen deposition had rematkable effects on sucrase, amylase, cellukse, polyphenol oxidase and p-gjucosidase in the soil layer of 0-20 cm （p 〈 0.05） and unrematkable effects on catalase and urease （p 〉 0.05）; in the soil layer of 2CM0 cm, the response made by suctase, catalase, urease, amylase, cellulase, polyphenol oxidase and p-glucosidase to nitrogen deposition reached a significant level 〈 0.05）.② In the soil layer of 0-20 cm, the activity of ufease and polyphenol oxidase reduced under LN treatment and enhanced under HN treatment, and the activity of invertase, catalase, amylase, cellulose, and p-glucosidase was inhibited by nitrogen deposition. ③In the soil layer of 2CM0 cm, the activity of polyphenol oxidase and p-glucosidase reduced under under LN treatment and enhanced under HN treatment, and the activity of invertase, catalase, urease, amylase, and cellulase was inhibited by nitrogen deposition. ④ With the deepening of the boundary soil layer （from 0-20 cm to 20-40 cm）, urease and pucosidase made different responses to the different levels of nitrogen deposition, while invertase, catakse, amylase, cellulose, and polyphenol oxidase showed the same response to nitrogen deposition.展开更多
The research analyzed the definition, differences and connection between fog and haze, as well as the formation causes, and the countermeasures were pro- posed, providing references for improving air quality in cities.
基金supported by the National Key Research and Development Program of China[grant number2016YFA0600703]National Science Foundation of China[grant number 41421004]Chinese Academy of Sciences-Peking University(CAS-PKU)partnership program
文摘In recent years, haze pollution events in Beijing have increased sharply, and the haze pollution of Beijing in October 2016 reached a new high. Meteorological conditions are thought to have influences on the haze occurrence, yet the associated atmospheric circulation of haze in October and why the most severe haze pollution occurred in 2016 is still unclear. Here, the authors show through daily observation and reanalysis data that key regions of North Atlantic and North Pacific sea surface temperature （SST） anomalies may be the main factors for this most severe haze event. Since 2013, the SSTs of these two key regions have increased dramatically and reached a peak, which could have induced the severe haze pollution by affecting the Eurasia teleconnection （EU） and the North Pacific Oscillation, with these factors then providing favorable dynamic and thermodynamic conditions for haze development.
基金supported by the National Natural Science Foundation of China[grant number 41590874]and[grant number41590875]
文摘Satellite remote sensing is very important to obtain a variety of cloud properties. However, the data quality from satellites varies with different satellite characteristics. From December 2015 to January 2016, ground-based air quality index （AQI） data showed severe haze events occurred successively in eastern China, particularly in the Beijing-Tianjin-Hebei region. During those days, a red alert （the most serious level）, orange alert （the second-highest level）, and yellow alert （the third-highest level） for haze, were issued in Beijing. Cloud detection from four sensors onboard the ＇A-Train＇satellite constellation were compared for two severe haze episodes, on 21 and 30 December 2015 respectively. Results showed that the MODIS sensor onboard the Aqua satellite misclassified aerosol as cloud, while the other three sensors-AIRS onboard Aqua, the cloud profiling radar onboard CloudSat, and CALIOP onboard CALIPSO-did not observe cloud over the same location. Through the high-AQI haze region in the CALIPSO and CloudSat orbit track, MODIS marked cloud close to the surface, while the MODIS true-color image and CALIOP observed an aerosol layer over the same location, suggesting MODIS falsely observed cloud there. Over the haze region in eastern China, MODIS observed 36% on average greater cloud fraction than AIRS, suggesting haze pollution induces a greater MODIS cloud amount.
基金Supported by the National Key Research and Development Program of China [grant numbers 2017YFC0209600 and 2016YFC0208802]
文摘Beijing experienced serious haze pollution from 24 November 2015 to 2 December 2015.To investigate the planetary boundary layer characteristics,especially turbulence characteristics,the authors analyzed the wind,temperature,humidity,and turbulence characteristics during heavily polluted weather by using the observational data of the 325-m meteorological tower in Beijing.The results indicate that the pollution was mainly caused by the easterly and southerly winds.There were negative correlations between wind speed,turbulent kinetic energy,friction velocity,and the PM2.5 concentration.During clean days,the wind speed greatly enhanced with height;however,during the period of heavy pollution,the wind speed changed a little from the nearsurface layer to the top of the tower.In contrast,the spatial variability of TKE from the nearsurface layer to the upper layer was not so obvious.The heavy haze pollution in this study was often characterized by the emergence of an inversion layer;therefore,the diurnal variation of the boundary layer temperature was very small.At the time of serious pollution,the relative humidity was near 100%.The diurnal variations of sensible heat flux and water vapor flux were significantly reduced when severe pollution occurred.
文摘The characters of foggy day, misty day and hazy day were analyzed based on information in 7 meteorological stations in Xi’an during 1960 -2012. The results showed that during 1960-2012 in Xi’an, foggy day occurs most in mountainous regions and few in plains; misty day occurs most in cities and few in suburbs; hazy day occurs most in cities, followed by inner and outer suburbs. Annual foggy day in Xi’an changed from increasing to decreasing; misty day was increasing by 9.0 d/10 a; hazy day was decreasing by -7.7 d/10 a. During the 53 y in Xi’an, foggy day was shown in a singly-valley shape, and the minimum appeared in summer and the maximum appeared in winter; misty day was shown in a ＂V＂-shape, and the minimum （7.6 d） appeared in June and the maximum （3.8 d） in December; hazy day was shown in a ＂U＂-shape from May to September and the maximum in January （6.1）.
基金Sponsored by National Natural Science Fund of China(31360119,31460112)2015 Pilot Project of Excellent Agriculture and Forestry Talents Cultivation Program Reform
文摘The simulated nitrogen deposition [control check （CBQ, 0 kg＇hm^2 /a; low nitrogen （LN）, 25 kg-hm^2 /a; medium nitrogen （MN）, 50 kg-hm^2/a high nitrogen （HN）, 150 kg·hm^2 /a] was performed from July 2014 to August 2015 in the fotest-gtassland boundary in Zhuqudeng Village, Bujiu Township, Iinzhi City, Tibet Autonomous Regioii to analyze the activity of enzymes （invertase, catalase, ufease, amylase, cellukse, polyphenol oxidase, and p-glucosidase） in soil layers of 0-20 cm and 20-40 cm and explore die effect of different levels of nitrogen deposition on enzyme activity different layers of soiL The results showed tiiat＇ ① different levels of simulated nitrogen deposition had rematkable effects on sucrase, amylase, cellukse, polyphenol oxidase and p-gjucosidase in the soil layer of 0-20 cm （p 〈 0.05） and unrematkable effects on catalase and urease （p 〉 0.05）; in the soil layer of 2CM0 cm, the response made by suctase, catalase, urease, amylase, cellulase, polyphenol oxidase and p-glucosidase to nitrogen deposition reached a significant level 〈 0.05）.② In the soil layer of 0-20 cm, the activity of ufease and polyphenol oxidase reduced under LN treatment and enhanced under HN treatment, and the activity of invertase, catalase, amylase, cellulose, and p-glucosidase was inhibited by nitrogen deposition. ③In the soil layer of 2CM0 cm, the activity of polyphenol oxidase and p-glucosidase reduced under under LN treatment and enhanced under HN treatment, and the activity of invertase, catalase, urease, amylase, and cellulase was inhibited by nitrogen deposition. ④ With the deepening of the boundary soil layer （from 0-20 cm to 20-40 cm）, urease and pucosidase made different responses to the different levels of nitrogen deposition, while invertase, catakse, amylase, cellulose, and polyphenol oxidase showed the same response to nitrogen deposition.
文摘The research analyzed the definition, differences and connection between fog and haze, as well as the formation causes, and the countermeasures were pro- posed, providing references for improving air quality in cities.
