期刊文献+
共找到137,580篇文章
< 1 2 250 >
每页显示 20 50 100
Operating Parameters of the District Heating Substation Cooperating With the Installation of Technological Air Conditioning With High Efficiency of Heat Recovery
1
作者 Żarski Kazimierz Kryża Mariusz 《Chinese Business Review》 2024年第1期1-12,共12页
The article analyses the problem of determining the operating parameters of the district heating substation cooperating with the air heating system in technological air conditioning systems equipped with heat exchange... The article analyses the problem of determining the operating parameters of the district heating substation cooperating with the air heating system in technological air conditioning systems equipped with heat exchangers with high efficiency of heat recovery.Attention was paid to the correct selection of heat exchangers for the heat output balance depending on the heat recovery protection algorithms against a drop in the temperature of the heat transfer surface below 0℃.Critical parameters were determined in Polish climatic conditions,at which the operation of the heat recovery exchanger in the air conditioning system is switched off or limited.It has been proven that the proper functioning of the district heating substation cooperating with the installation of air conditioning with high heat recovery efficiency requires the use of two heat exchangers with different characteristics,equipped with properly selected temperature control systems.The optimal model of cooperation between the technological air conditioning system and the heating substation was also indicated. 展开更多
关键词 ventilation of operating theatre air conditioning flow control in heating circuit
下载PDF
Characteristics of air pollution events over Hotan Prefecture at the southwestern edge of Taklimakan Desert, China 被引量:5
2
作者 LI Jingxin WANG Shigong +4 位作者 CHU Jinhua WANG Jiaxin LI Xu YUE Man SHANG Kezheng 《Journal of Arid Land》 SCIE CSCD 2018年第5期686-700,共15页
Hotan Prefecture is located at the southwestern edge of Taklimakan Desert, the world's largest shifting sand desert, of China. The desert is one of the main sources for frequent sand-dust weather events which strongl... Hotan Prefecture is located at the southwestern edge of Taklimakan Desert, the world's largest shifting sand desert, of China. The desert is one of the main sources for frequent sand-dust weather events which strongly affect the air quality of Hotan Prefecture. Although this region is characterized by the highest annual mean PMlo concentration values that are routinely recorded by environmental monitoring stations across China, both this phenomenon and its underlying causes have not been adequately addressed in previous researches. Reliable pollutant PM_10 data are currently retrieved using a tapered element oscillating microbalance (TEOM) 1400a, a direct real-time monitor, while additional concentration values including for PM_2.5, sulfur dioxide (SO_2), nitrogen dioxide (NO_2), carbon monoxide (CO) and ozone (O_3) have been collected in recent years by the Hotan Environmental Monitoring Station. Based on these data, this paper presents a comparison of the influences of different kinds of sand-dust weather events on PM_10 (or PM_2.5) as well as the concentrations of other gaseous pollutants in Hotan Prefecture. It is revealed that the highest monthly average PM_10 concentrations are observed in the spring because of the frequent occurrence of three distinct kinds of sand-dust weather events at this time, including dust storms, blowing dust and floating dust. The floating dust makes the most significant contribution to PM_10 (or PM_2.5) concentration in this region, a result that differs from eastern Chinese cities where the heaviest PM_10 pollution occurs usually in winter and air pollution results from the excess emission of local anthropogenic pollutants. It is also shown that PM_10 concentration varies within wpical dust storms. PM_10 concentrations vary among 20 dust storm events within Hotan Prefecture, and the hourly mean concentrations tend to sharply increase initially then slowly decreasing over time. Data collected from cities in eastern China show the opposite with the hourly mean PM_10 (or PM_2.5) concentration tending to slowly increase then sharply decrease during heavy air pollution due to the excess emission of local anthropogenic pollutants. It is also found that the concentration of gaseous pollutants during sand-dust weather events tends to be lower than those cases under clear sky conditions. This indicates that these dust events effectively remove and rapidly diffuse gaseous pollutants. The analysis also shows that the concentration of SO_2 decreases gradually at the onset of all three kinds of sand-dust weather events because of rapidly increasing wind velocity and the development of favorable atmospheric conditions for diffusion. In contrast, changes in O_3 and NO_2 concentrations conformed to the opposite pattern during all three kinds of sand-dust weather events within this region, implying the inter transformation of these gas species during these events. 展开更多
关键词 PM10 (or PM2.5) concentration sand-dust weather events gaseous pollutants air pollution Taklimakan Desert
下载PDF
Feasibility Research on the High Speed Rotary Positive Air Filter
3
作者 阎为革 刘淑艳 《Journal of Beijing Institute of Technology》 EI CAS 2000年第2期166-170,共5页
The structure, separation principle and feasibility research for a new type of vehicle air filter called the high speed rotary positive air filter were described. The analysis of the experimental data showed that the ... The structure, separation principle and feasibility research for a new type of vehicle air filter called the high speed rotary positive air filter were described. The analysis of the experimental data showed that the principle and structure of it were feasible and it possessed high separation efficiency and great self cleaning ability. Compared with the conventional air filter it also has lower air intake loss. So it is worth further practical research. 展开更多
关键词 internal combustion engine air filter airflow capacity separation efficiency air intake loss
下载PDF
A Preliminary Analysis of the Relationship between Longan Canopy Temperature and Air Temperature during Overwintering Period 被引量:2
4
作者 蒙文交 谭宗琨 刘春峰 《Agricultural Science & Technology》 CAS 2008年第4期82-86,136,共6页
[Objective] The study aimed to provide supports for developing chilling and freezing injury monitoring and disaster damage assessment of longan(Dimocarpus Longan Lour.).[Method] Based on field observation data,the rel... [Objective] The study aimed to provide supports for developing chilling and freezing injury monitoring and disaster damage assessment of longan(Dimocarpus Longan Lour.).[Method] Based on field observation data,the relationships between longan canopy temperature and air temperature under different weather types(sunny,cloudy to sunny,cloudy,rainy,radiation chilling injury and advection chilling injury)in 2007-2008 winter were analyzed.[Result] Diurnal variations of longan canopy temperature under sunny and radiation chilling injury weather conditions were most dramatic,followed with those under cloudy to sunny condition,while variations under cloudy,rainy and advection chilling injury conditions were mild.Diurnal variations of orchard air temperature were also closely related to weather types.By using linear and curvilinear regression methods,the relationship models between longan canopy temperature and observation station air temperature were established.The models for cloudy,rainy and advection chilling injury had better effects than those for sunny,cloudy to sunny and radiation chilling injury;the models for night were better than those for daytime and the whole day.[Conclusion] To some extent,applying the relationship models between longan canopy temperature and observation station air temperature could make up the shortcoming of meteorological data which were higher than the real values. 展开更多
关键词 Longan(Dimocarpus LONGAN Lour.) CANOPY TEMPERATURE air TEMPERATURE FREEZING INJURY Model
下载PDF
Formation of the Summertime Ozone Valley over the Tibetan Plateau:The Asian Summer Monsoon and Air Column Variations 被引量:22
5
作者 卞建春 严仁嫦 +2 位作者 陈洪滨 吕达仁 Steven T.MASSIE 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2011年第6期1318-1325,共8页
The summertime ozone valley over the Tibetan Plateau is formed by two influences,the Asian summer monsoon(ASM) and air column variations.Total ozone over the Tibetan Plateau in summer was ~33 Dobson units(DU) low... The summertime ozone valley over the Tibetan Plateau is formed by two influences,the Asian summer monsoon(ASM) and air column variations.Total ozone over the Tibetan Plateau in summer was ~33 Dobson units(DU) lower than zonal mean values over the ocean at the same latitudes during the study period 2005-2009.Satellite observations of ozone profiles show that ozone concentrations over the ASM region have lower values in the upper troposphere and lower stratosphere(UTLS) than over the non-ASM region.This is caused by frequent convective transport of low-ozone air from the lower troposphere to the UTLS region combined with trapping by the South Asian High.This offset contributes to a ~20-DU deficit in the ozone column over the ASM region.In addition,along the same latitude,total ozone changes identically with variations of the terrain height,showing a high correlation with terrain heights over the ASM region,which includes both the Tibetan and Iranian plateaus.This is confirmed by the fact that the Tibetan and Iranian plateaus have very similar vertical distributions of ozone in the UTLS,but they have different terrain heights and different total-column ozone levels.These two factors(lower UTLS ozone and higher terrain height) imply 40 DU in the lower-ozone column,but the Tibetan Plateau ozone column is only ~33 DU lower than that over the non-ASM region.This fact suggests that the lower troposphere has higher ozone concentrations over the ASM region than elsewhere at the same latitude,contributing ~7 DU of total ozone,which is consistent with ozonesonde and satellite observations. 展开更多
关键词 Asian summer monsoon Tibetan Plateau air column variation ozone valley
下载PDF
A Decadal Shift of Summer Surface Air Temperature over Northeast Asia around the Mid-1990s 被引量:17
6
作者 CHEN Wei LU Riyu 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2014年第4期735-742,共8页
This study identifies a decadal shift of summer surface air temperature (SAT) over Northeast Asia,including southeastern parts of Russia,Mongolia and northern China,around the mid-1990s.The results suggest that the ... This study identifies a decadal shift of summer surface air temperature (SAT) over Northeast Asia,including southeastern parts of Russia,Mongolia and northern China,around the mid-1990s.The results suggest that the SAT over the Northeast Asia experienced a significant warming after 1994 relative to that before 1993.This decadal shift also extends to northern China,and leads to a warmer summer over Northeast China and North China after the mid-1990s.The decadal warming over Northeast Asia is found to concur with the enhancement of South China rainfall around the mid-1990s.On the one hand,both the Northeast Asian SAT and South China rainfall exhibit this mid-1990s decadal shift only in summer,but not in other seasons.On the other hand,both the Northeast Asian SAT and South China rainfall exhibit this mid-1990s decadal shift not only in the summer seasonal mean,but also in each month of summer (June,July and August).Furthermore,the decadal warming is found to result from an anticyclonic anomaly over Northeast Asia,which can be interpreted as the response to the increased precipitation over South China,according to previous numerical results.Thus,we conclude that the warming shift of summer Northeast Asian SAT around the mid-1990s was a remote response to the increased precipitation over South China. 展开更多
关键词 surface air temperature Northeast Asia decadal shift mid-1990s South China rainfall
下载PDF
Modeling of the whole process of shock wave overpressure of freefield air explosion 被引量:7
7
作者 Zai-qing Xue Shunping Li +2 位作者 Chun-liang Xin Li-ping Shi Hong-bin Wu 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2019年第5期815-820,共6页
The waveform of the explosion shock wave under free-field air explosion is an extremely complex problem.It is generally considered that the waveform consists of overpressure peak,positive pressure zone and negative pr... The waveform of the explosion shock wave under free-field air explosion is an extremely complex problem.It is generally considered that the waveform consists of overpressure peak,positive pressure zone and negative pressure zone.Most of current practice usually considers only the positive pressure.Many empirical relations are available to predict overpressure peak,the positive pressure action time and pressure decay law.However,there are few models that can predict the whole waveform.The whole process of explosion shock wave overpressure,which was expressed as the product of the three factor functions of peak,attenuation and oscillation,was proposed in the present work.According to the principle of explosion similarity,the scaled parameters were introduced and the empirical formula was absorbed to form a mathematical model of shock wave overpressure.Parametric numerical simulations of free-field air explosions were conducted.By experimental verification of the AUTODYN numerical method and comparing the analytical and simulated curves,the model is proved to be accurate to calculate the shock wave overpressure under free-field air explosion.In addition,through the model the shock wave overpressure at different time and distance can be displayed in three dimensions.The model makes the time needed for theoretical calculation much less than that for numerical simulation. 展开更多
关键词 air explosion Shock WAVE overPRESSURE Free field Experimental VERIFICATION NUMERICAL simulation
下载PDF
Variation in Summer Surface Air Temperature over Northeast Asia and Its Associated Circulation Anomalies 被引量:8
8
作者 Wei CHEN Xiaowei HONG +6 位作者 Riyu LU Aifen JIN Shizhu JIN Jae-Cheol NAM Jin-Ho SHIN Tae-Young GOO Baek-Jo KIM 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2016年第1期1-9,共9页
This study investigates the interannual variation of summer surface air temperature over Northeast Asia(NEA) and its associated circulation anomalies.Two leading modes for the temperature variability over NEA are ob... This study investigates the interannual variation of summer surface air temperature over Northeast Asia(NEA) and its associated circulation anomalies.Two leading modes for the temperature variability over NEA are obtained by EOF analysis.The first EOF mode is characterized by a homogeneous temperature anomaly over NEA and therefore is called the NEA mode.This anomaly extends from southeast of Lake Baikal to Japan,with a central area in Northeast China.The second EOF mode is characterized by a seesaw pattern,showing a contrasting distribution between East Asia(specifically including the Changbai Mountains in Northeast China,Korea,and Japan) and north of this region.This mode is named the East Asia(EA) mode.Both modes contribute equivalently to the temperature variability in EA.The two leading modes are associated with different circulation anomalies.A warm NEA mode is associated with a positive geopotential height anomaly over NEA and thus a weakened upper-tropospheric westerly jet.On the other hand,a warm EA mode is related to a positive height anomaly over EA and a northward displaced jet.In addition,the NEA mode tends to be related to the Eurasian teleconnection pattern,while the EA mode is associated with the East Asia-Pacific/PacificJapan pattern. 展开更多
关键词 surface air temperature Northeast Asia East Asia circulation anomaly interannual variability
下载PDF
A Microscale Model for Air Pollutant Dispersion Simulation in Urban Areas: Presentation of the Model and Performance over a Single Building 被引量:3
9
作者 Ning ZHANG Yunsong DU Shiguang MIAO 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2016年第2期184-192,共9页
A microscale air pollutant dispersion model system is developed for emergency response purposes. The model includes a diagnostic wind field model to simulate the wind field and a random-walk air pollutant dispersion m... A microscale air pollutant dispersion model system is developed for emergency response purposes. The model includes a diagnostic wind field model to simulate the wind field and a random-walk air pollutant dispersion model to simulate the pollutant concentration through consideration of the influence of urban buildings. Numerical experiments are designed to evaluate the model's performance, using CEDVAL (Compilation of Experimental Data for Validation of Microscale Disper- sion Models) wind tunnel experiment data, including wind fields and air pollutant dispersion around a single building. The results show that the wind model can reproduce the vortexes triggered by urban buildings and the dispersion model simulates the pollutant concentration around buildings well. Typically, the simulation errors come from the determination of the key zones around a building or building cluster. This model has the potential for multiple applications; for example, the prediction of air pollutant dispersion and the evaluation of environmental impacts in emergency situations; urban planning scenarios; and the assessment of microscale air quality in urban areas. 展开更多
关键词 numerical model urban air pollution air pollutant dispersion emergency response model
下载PDF
Spatial Variation in CO_(2) Concentration Improves the Simulated Surface Air Temperature Increase in the Northern Hemisphere 被引量:1
10
作者 Jing PENG Li DAN Xiba TANG 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2024年第8期1614-1628,1676-1685,共25页
The increasing concentration of atmospheric CO_(2) since the Industrial Revolution has affected surface air temperature.However,the impact of the spatial distribution of atmospheric CO_(2) concentration on surface air... The increasing concentration of atmospheric CO_(2) since the Industrial Revolution has affected surface air temperature.However,the impact of the spatial distribution of atmospheric CO_(2) concentration on surface air temperature biases remains highly unclear.By incorporating the spatial distribution of satellite-derived atmospheric CO_(2) concentration in the Beijing Normal University Earth System Model,this study investigated the increase in surface air temperature since the Industrial Revolution in the Northern Hemisphere(NH) under historical conditions from 1976-2005.In comparison with the increase in surface temperature simulated using a uniform distribution of CO_(2),simulation with a nonuniform distribution of CO_(2)produced better agreement with the Climatic Research Unit(CRU) data in the NH under the historical condition relative to the baseline over the period 1901-30.Hemispheric June-July-August(JJA) surface air temperature increased by 1.28℃ ±0.29℃ in simulations with a uniform distribution of CO_(2),by 1.00℃±0.24℃ in simulations with a non-uniform distribution of CO_(2),and by 0.24℃ in the CRU data.The decrease in downward shortwave radiation in the non-uniform CO_(2) simulation was primarily attributable to reduced warming in Eurasia,combined with feedbacks resulting from increased leaf area index(LAI) and latent heat fluxes.These effects were more pronounced in the non-uniform CO_(2)simulation compared to the uniform CO_(2) simulation.Results indicate that consideration of the spatial distribution of CO_(2)concentration can reduce the overestimated increase in surface air temperature simulated by Earth system models. 展开更多
关键词 spatial variations of CO_(2) surface air temperature Earth system model land surface albedo leaf area index
下载PDF
Co/CoO heterojunction rich in oxygen vacancies introduced by O_(2) plasma embedded in mesoporous walls of carbon nanoboxes covered with carbon nanotubes for rechargeable zinc-air battery 被引量:1
11
作者 Leijun Ye Weiheng Chen +1 位作者 Zhong-Jie Jiang Zhongqing Jiang 《Carbon Energy》 SCIE EI CAS CSCD 2024年第7期14-25,共12页
Herein,Co/CoO heterojunction nanoparticles(NPs)rich in oxygen vacancies embedded in mesoporous walls of nitrogen-doped hollow carbon nanoboxes coupled with nitrogen-doped carbon nanotubes(P-Co/CoOV@NHCNB@NCNT)are well... Herein,Co/CoO heterojunction nanoparticles(NPs)rich in oxygen vacancies embedded in mesoporous walls of nitrogen-doped hollow carbon nanoboxes coupled with nitrogen-doped carbon nanotubes(P-Co/CoOV@NHCNB@NCNT)are well designed through zeolite-imidazole framework(ZIF-67)carbonization,chemical vapor deposition,and O_(2) plasma treatment.As a result,the threedimensional NHCNBs coupled with NCNTs and unique heterojunction with rich oxygen vacancies reduce the charge transport resistance and accelerate the catalytic reaction rate of the P-Co/CoOV@NHCNB@NCNT,and they display exceedingly good electrocatalytic performance for oxygen reduction reaction(ORR,halfwave potential[EORR,1/2=0.855 V vs.reversible hydrogen electrode])and oxygen evolution reaction(OER,overpotential(η_(OER,10)=377mV@10mA cm^(−2)),which exceeds that of the commercial Pt/C+RuO_(2) and most of the formerly reported electrocatalysts.Impressively,both the aqueous and flexible foldable all-solid-state rechargeable zinc-air batteries(ZABs)assembled with the P-Co/CoOV@NHCNB@NCNT catalyst reveal a large maximum power density and outstanding long-term cycling stability.First-principles density functional theory calculations show that the formation of heterojunctions and oxygen vacancies enhances conductivity,reduces reaction energy barriers,and accelerates reaction kinetics rates.This work opens up a new avenue for the facile construction of highly active,structurally stable,and cost-effective bifunctional catalysts for ZABs. 展开更多
关键词 HETEROJUNCTION oxygen evolution/reduction reaction oxygen vacancies rechargeable zinc–air battery three‐dimensional nitrogen‐doped hollow carbon nanoboxes
下载PDF
Changes and spatial patterns of the differences between ground and air temperature over the Qinghai-Xizang Plateau 被引量:5
12
作者 ZHANG Wengang LI Shuxun +1 位作者 WU Tonghua PANG Qiangqiang 《Journal of Geographical Sciences》 SCIE CSCD 2007年第1期20-32,共13页
The difference between ground soil and air temperature (Ts-Ta) was studied by using the data of ground and air temperature of 99 stations over the Qinghai-Xizang (Tibet) Plateau from 1960 to 2000,and its spatial d... The difference between ground soil and air temperature (Ts-Ta) was studied by using the data of ground and air temperature of 99 stations over the Qinghai-Xizang (Tibet) Plateau from 1960 to 2000,and its spatial distribution and time changing tendency have been diagnosed by principal component analysis and power spectral analysis methods. The results show that the values of (Ts-Ta) are the maximum in June and the minimum in December. The first three loading eigenvectors, which reflect the main spatially anomalous structure of (Ts-Ta) over the Qinghai-Xizang Plateau, contain the contrary changing pattern between the northwestern and the southeastern regions, the pattern response of the sea level elevation and the geography, and the pattern response of the distribution of the permafrost. There are four patterns of time evolution including the patterns of monotonous increasing or decreasing trends, the basic stability pattern and the parabola pattern with the minimum value. (Ts-Ta) has a periodic variation about 2 years. According to the spatial distribution of the third loading eigenvectors of (Ts-Ta) over the Qinghai-Xizang Plateau in cold season, the permafrost response region and the seasonal frozen ground response region are identified. 展开更多
关键词 Qinghai-Xizang Plateau difference between ground and air temperature (Ts-Ta) principal component temperature subarea
下载PDF
Some Characteristics of the Surface Boundary Layer of a Strong Cold Air Process over Southern China 被引量:2
13
作者 刘熙明 程雪玲 +2 位作者 吴琼 傅敏宁 曾庆存 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2013年第1期210-218,共9页
In southern China, cold air is a common weather process during the winter season; it can cause strong wind, sharp temperature decreases, and even the snow or freezing rain events. However, the features of the atmosphe... In southern China, cold air is a common weather process during the winter season; it can cause strong wind, sharp temperature decreases, and even the snow or freezing rain events. However, the features of the atmospheric boundary layer during cold air passage are not clearly understood due to the lack of comprehensive observation data, especially regarding turbulence. In this study, four-layer gradient meteorological observation data and one-layer, 10-Hz ultrasonic anemometer-thermometer monitoring data from the northern side of Poyang Lake were employed to study the main features of the surface boundary layer during a strong cold-air passage over southern China. The results show that, with the passage of a cold air front, the wind speed exhibits low-frequency variations and that the wind systematically descends. During the strong wind period, the wind speed increases with height in the surface layer. Regular gust packets are superimposed on the basic strong wind flow. Before the passage of cold air, the wind gusts exhibit a coherent structure. The wind and turbulent momentum fluxes are small, although the gusty wind momentum flux is slightly larger than the turbulent momentum flux. However, during the invasion of cold air, both the gusty wind and turbulent momentum fluxes increase rapidly with wind speed, and the turbulent momentum flux is larger than the gusty wind momentum flux during the strong wind period. After the cold air invasion, this structure almost disappears. 展开更多
关键词 cold air surface boundary layer gusty wind descending motion
下载PDF
Changes of Air–sea Coupling in the North Atlantic over the 20th Century 被引量:2
14
作者 YANG Yun WU Lixin 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2015年第4期445-456,共12页
Changes of air–sea coupling in the North Atlantic Ocean over the 20 th century are investigated using reanalysis data,climate model simulations, and observational data. It is found that the ocean-to-atmosphere feedba... Changes of air–sea coupling in the North Atlantic Ocean over the 20 th century are investigated using reanalysis data,climate model simulations, and observational data. It is found that the ocean-to-atmosphere feedback over the North Atlantic is significantly intensified in the second half of the 20 th century. This coupled feedback is characterized by the association between the summer North Atlantic Horseshoe(NAH) SST anomalies and the following winter North Atlantic Oscillation(NAO). The intensification is likely associated with the enhancement of the North Atlantic storm tracks as well as the NAH SST anomalies. Our study also reveals that most IPCC AR4 climate models fail to capture the observed NAO/NAH coupled feedback. 展开更多
关键词 air–sea coupling climate change North Atlantic Ocean 20th Century
下载PDF
STUDY OF THE VERTICAL WIND FIELD STRUCTURE AND ITS RELATIONSHIP WITH PM2.5 AIR POLLUTION OVER THE PEARL RIVER DELTA IN AUTUMN 被引量:2
15
作者 WU Meng LUO Yun +3 位作者 ZHENG Yan-ping WU Xiao-xun FAN Shao-jia WU Dui 《Journal of Tropical Meteorology》 SCIE 2020年第1期82-92,共11页
Meteorological conditions,particularly the vertical wind field structure,have a direct influence on the PM2.5 concentrations over the Pearl River Delta(PRD).In October 2012,an exceptional air pollution event occurred ... Meteorological conditions,particularly the vertical wind field structure,have a direct influence on the PM2.5 concentrations over the Pearl River Delta(PRD).In October 2012,an exceptional air pollution event occurred in the PRD,and a high concentration of PM2.5 was registered at some stations.During days with PM2.5 air pollution,the wind speed was less than 3 m s-1 at the surface,and the vertical wind field featured a weak wind layer(WWL)with a thickness of approximately 1000 m.The mean atmospheric boundary layer height was less than 500 m during pollution days,but it was greater than 1400 m during non-pollution days.A strong negative correlation was detected between the PM2.5 concentration and the ventilation index(VI).The VI was less than 2000 m2 s-1 during PM2.5 air pollution days.Because of the weak wind,sea-land breezes occurred frequently,the recirculation factor(RF)values were small at a height of 800 m during pollution days,and the zones with the lowest RF values always occurred between the heights of 300 and 600 m.The RF values during PM2.5 pollution days were approximately 0.4 to 0.6 below a height of 800 m,reducing the transportation capacity of the wind field to only 40%to 60%.The RF and wind profile characteristics indicated that sealand breezes were highly important in the accumulation of PM2.5 air pollution in the PRD.The sea breezes may transport pollutants back inland and may result in the peak PM2.5 concentrations at night. 展开更多
关键词 atmospheric environment air quality recirculation factor sea-land breezes
下载PDF
Impact of the Kuroshio Extension Oceanic Front on Autumn and Winter Surface Air Temperatures over North America 被引量:1
16
作者 YUAN Li XIAO Ziniu 《Journal of Ocean University of China》 SCIE CAS CSCD 2018年第4期713-720,共8页
Mid-latitude air-sea interaction is an important topic that attracts a considerable amount of research interest. The Kuroshio Extension(KE) is one of the main western boundary currents and plays a critical role in the... Mid-latitude air-sea interaction is an important topic that attracts a considerable amount of research interest. The Kuroshio Extension(KE) is one of the main western boundary currents and plays a critical role in the mid-latitude atmospheric circulation. This paper uses the NCEP/NCAR reanalysis and Hadley sea surface temperature datasets to investigate the influence of oceanic fronts in the KE region on surface air temperature in North America over the period 1949–2014. A significant correlation was found between the KE front intensity and the temperatures over North America in autumn and winter. A strong(weak) KE front anomaly in autumn is associated with an increasing(decreasing) surface temperature over western North America but a decreasing(increasing) surface temperature over eastern North America. In winter, central North America warms(cools) when the KE front is strong(weak). The response of the atmospheric circulation, including wind in the high and low troposphere, troughs, and ridges, to the strengthening(weakening) of the KE front is the main cause of these changes in surface temperature. 展开更多
关键词 KUROSHIO EXTENSION surface air temperature NORTH AMERICA
下载PDF
Evaluation of Surface Air Temperature Change over China and the Globe during the Twentieth Century in IAP AGCM4.0 被引量:12
17
作者 DONG Xiao XUE Feng +1 位作者 ZHANG He ZENG Qing-Cun 《Atmospheric and Oceanic Science Letters》 2012年第5期435-438,共4页
Based on time series and linear trend analysis, the authors evaluated the performance of the fourth gen- eration atmospheric general circulation model developed at the Institute of Atmospheric Physics, Chinese Academy... Based on time series and linear trend analysis, the authors evaluated the performance of the fourth gen- eration atmospheric general circulation model developed at the Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP AGCM4.0), in simulating surface air temperature (SAT) during the twentieth century over China and the globe. The numerical experiment is con- ducted by driving the model with the observed sea surface temperature and sea ice. It is shown that IAP AGCM4.0 can simulate the warming trend of the global SAT, with the major wanning regions in the high latitudes of the Northern Hemisphere and the mid-latitudes of the South- ern Hemisphere. While the simulated trend over the whole globe is close to the observation, the model trader- estimates the observed trend over the continents. More- over, the model simulates the spatial distribution of SAT in China, with a bias of approximately -2℃ in eastern China, but with a more serious bias in western China. Compared with the global mean, however, the correlation coefficient between the simulation and observation in China is significantly lower, indicating that there is large uncertainty in simulating regional climate change. 展开更多
关键词 IAP AGCM4.0 surface air temperature thetwentieth century globe China
下载PDF
Fluid-chemical modeling of the near-cathode sheath formation process in a high current broken in DC air circuit breaker
18
作者 彭世东 李静 +3 位作者 段薇 曹云东 刘树鑫 黄浩 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第1期523-538,共16页
When the contacts of a medium-voltage DC air circuit breaker(DCCB) are separated, the energy distribution of the arc is determined by the formation process of the near-electrode sheath. Therefore, the voltage drop thr... When the contacts of a medium-voltage DC air circuit breaker(DCCB) are separated, the energy distribution of the arc is determined by the formation process of the near-electrode sheath. Therefore, the voltage drop through the near-electrode sheath is an important means to build up the arc voltage, which directly determines the current-limiting performance of the DCCB. A numerical model to describe the near-electrode sheath formation process can provide insight into the physical mechanism of the arc formation, and thus provide a method for arc energy regulation. In this work, we establish a two-dimensional axisymmetric time-varying model of a medium-voltage DCCB arc when interrupted by high current based on a fluid-chemical model involving 16 kinds of species and 46 collision reactions. The transient distributions of electron number density, positive and negative ion number density, net space charge density, axial electric field, axial potential between electrodes, and near-cathode sheath are obtained from the numerical model. The computational results show that the electron density in the arc column increases, then decreases, and then stabilizes during the near-cathode sheath formation process, and the arc column's diameter gradually becomes wider. The 11.14 V–12.33 V drops along the17 μm space charge layer away from the cathode(65.5 k V/m–72.5 k V/m) when the current varies from 20 k A–80 k A.The homogeneous external magnetic field has little effect on the distribution of particles in the near-cathode sheath core,but the electron number density at the near-cathode sheath periphery can increase as the magnetic field increases and the homogeneous external magnetic field will lead to arc diffusion. The validity of the numerical model can be proven by comparison with the experiment. 展开更多
关键词 near-cathode sheath atmospheric pressure air arc fluid-chemical model high current DC air circuit breaker(DCCB)
下载PDF
Drought Response to Air Temperature Change over China on the Centennial Scale 被引量:3
19
作者 CHEN Huo-Po SUN Jian-Qi 《Atmospheric and Oceanic Science Letters》 CSCD 2015年第3期113-119,共7页
Climate data from the Climatic Research Unit (CRU) for the period 1901-2013 are used to investigate the drought response to air temperature change over China on the centennial scale. Drought is observed to have incr... Climate data from the Climatic Research Unit (CRU) for the period 1901-2013 are used to investigate the drought response to air temperature change over China on the centennial scale. Drought is observed to have increased evidently across China, except for some regions in eastern China. This increase is much stronger in northern China compared to southern China, especially in Northwest and North China. These change characteris- tics of drought are closely associated with air temperature change, with the severe droughts in the major drought episodes of the last century generally coinciding with higher temperatures. The significantly increasing trend of drought in China based on observations only appears when considering the effects of air temperature change, which can explain -49% of droughts in observations and 30%-65% of droughts in Coupled Model Intereomparison Project Phase 5 (CMIP5) model simulations. Furthermore, the response of drought to air temperature change generally increases as the drought time scale increases. Furthermore, drought shows relatively high sensitivity in spring and early summer in China on the centennial scale. 展开更多
关键词 DROUGHT air temperature RESPONSE centennial scale China
下载PDF
Performance of Regional Integrated Environment Modeling System (RIEMS) in the Simulation of Surface Air Temperature over East Asia 被引量:4
20
作者 Zhao De-Ming 《Atmospheric and Oceanic Science Letters》 2012年第2期145-150,共6页
Regional climate models (RCMs) have the potential for more detailed surface characteristic and mesoscale modeling results than general circulation models (GCMs).These advantages have drawn significant focus on RCM dev... Regional climate models (RCMs) have the potential for more detailed surface characteristic and mesoscale modeling results than general circulation models (GCMs).These advantages have drawn significant focus on RCM development in East Asia.The Regional Integrated Environment Modeling System,version 2.0 (RIEMS2.0),has been developed from an earlier RCM,RIEMS1.0,by the Key Laboratory of Regional ClimateEnvironment for Temperate East Asia (RCE-TEA) and Nanjing University.A numerical experiment covering 1979 to 2008 (simulation duration from 1 January 1978 to 31 December 2008) with a 50-km spatial resolution was performed to test the ability of RIEMS2.0 to simulate long-term climate and climate changes in East Asia and to provide a basis for further development and applications.The simulated surface air temperature (SAT) was compared with observed meteorological data.The results show that RIEMS2.0 simulation reproduced the SAT spatial distribution in East Asia but that it was underestimated.The simulated 30-year averaged SAT was approximately 2.0°C lower than the observed SAT.The annual and interannual variations in the averaged SAT and their anomalies were both well reproduced in the model.A further analysis of three sub-regions representing different longitudinal ranges showed that there is a good correlation and consistency between the simulated results and the observed data.The annual variations,interannual variations for the averaged SAT,and the anomalies in the three sub-regions were also captured well by the model.In summary,RIEMS2.0 shows stability and does well both in simulating the long-term SAT in East Asia and in expressing sub-regional characteristics. 展开更多
关键词 RIEMS2.0 surface air temperature CLIMATE simulation ability
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部