Using daily outgoing long-wave radiation （OLR） data from the National Oceanic and Atmospheric Administration （NOAA） and the National Center for Environmental Prediction/National Center for Atmospheric Research （N...Using daily outgoing long-wave radiation （OLR） data from the National Oceanic and Atmospheric Administration （NOAA） and the National Center for Environmental Prediction/National Center for Atmospheric Research （NCEP/NCAR） reanalysis data of geopotential height fields for 1979-2006, the relationship between persistent heavy rain events （PHREs） in the Huaihe River valley （HRV） and the distribution pattern of convective activity in the tropical western Pacific warm pool （WPWP） is investigated. Based on nine cases of PHREs in the HRV, common characteristics of the West Pacific subtropical high （WPSH） show that the northern edge of the WPSH continues to lie in the HRV and is associated with the persistent ＂north weak south strong＂ distribution pattern of convective activities in the WPWP. Composite analysis of OLR leading the circulation indicates that the response of the WPSH to OLR anomaly patterns lags by about 1-2 days. In order to explain the reason for the effects of the distribution pattern of convective activities in the WPWP on the persistent northern edge of the WPSH in the HRV, four typical persistent heavy and light rain events in the Yangtze River valley （YRV） are contrasted with the PHREs in the HRV. The comparison indicates that when the distribution pattern of the convective activities anomaly behaves in a weak （strong） manner across the whole WPWP, persistent heavy （light） rain tends to occur in the YRV. When the distribution pattern of the convective activities anomaly behaves according to the ＂north weak south strong＂ pattern in the WPWP, persistent heavy rain tends to occur in the HRV. The effects of the ＂north weak south strong＂ distribution pattern of convective activities on PHREs in the HRV are not obvious over the seasonal mean timescale, perhaps due to the non-extreme status of convective activities in the WPWP.展开更多
By using NCEP/NCAR daily reanalysis data and daily precipitation data of 740 stations in China, relationships between the position variation of the West Pacific subtropical high (WPSH) and the diabatic heating during ...By using NCEP/NCAR daily reanalysis data and daily precipitation data of 740 stations in China, relationships between the position variation of the West Pacific subtropical high (WPSH) and the diabatic heating during persistent and intense rains in the Yangtze-Huaihe Rivers basin are studied. The results show that the position variation of WPSH is closely associated with the diabatic heating. There are strong apparent heating sources and moisture sinks in both the basin (to the north of WPSH) and the north of Bay of Bengal (to the west of WPSH) during persistent and intense rain events. In the basin, Q 1z begins to increase 3 days ahead of intense rainfall, maximizes 2 days later and then reduces gradually, but it changes little after precipitation ends, thus preventing the WPSH from moving northward. In the north of Bay of Bengal, 2 days ahead of strong rainfall over the basin, Q 1z starts to increase and peaks 1 day after the rain occurs, leading to the westward extension of WPSH. Afterwards, Q 1z begins declining and the WPSH makes its eastward retreat accordingly. Based on the complete vertical vorticity equation, in mid-troposphere, the vertical variation of heating in the basin is favorable to the increase of cyclonic vorticity north of WPSH, which counteracts the northward movement of WPSH and favors the persistence of rainbands over the basin. The vertical variation of heating in the north of Bay of Bengal is in favor of the increase of anti-cyclonic vorticity to the west of WPSH, which induces the westward extension of WPSH.展开更多
Atmospheric wet deposition plays an important role in the supply of nutrients and toxic substances to terrestrial and aquatic environments. Although long-term（e.g. annual, multi-year） wet deposition is recorded well...Atmospheric wet deposition plays an important role in the supply of nutrients and toxic substances to terrestrial and aquatic environments. Although long-term（e.g. annual, multi-year） wet deposition is recorded well, pronounced and short-term changes in precipitation chemistry are less well investigated. In the present study, the precipitation chemistry and scavenging ratio of air pollutants were observed during an extreme torrential rain event（325.6 mm at the observation site） that occurred over 19–21 July 2016 in the North China Plain（NCP）. The scavenging ratio of particles showed a similar spatial distribution to that of the precipitation amount in the NCP, indicating the efficient removal of particulate matter due to the large amount and precipitation intensity of the storm. In addition, the scavenging ratio of water soluble ions was larger than that of organics and gaseous pollutants such as SO_2 and NO_2, likely due to their differences in water solubility.Consequently, raindrops incorporated more aerosol sulfate than gaseous compounds. Due to the heavy precipitation amount, almost all species in rainwater during this storm showed their lowest concentration but the highest flux compared with other rain events, indicating an important role played by this storm in terms of the substances received by the terrestrial and marine ecosystems of the region. However, the contribution of this storm to the annual chemical flux was lower than that of precipitation amount, indicating that the atmospheric compounds were scavenged below-cloud first and were then diluted by the cloud/rainwater. Future studies are needed in the context of the occurrence of extreme rainfall events in the NCP from the perspective of climate variability.展开更多
Based on the daily precipitation data of nine stations representing the Xijiang River valley and the National Center for Environmental Prediction/National Center for Atmospheric Research (USA) reanalysis data, this st...Based on the daily precipitation data of nine stations representing the Xijiang River valley and the National Center for Environmental Prediction/National Center for Atmospheric Research (USA) reanalysis data, this study uses the wavelet analysis and band-pass filter methods to investigate the atmospheric intraseasonal oscillation characteristics of flood-causing rainstorms in the valley during the annually first raining seasons in 1968, 1994, 1998, 2002 and 2005. Results show that the daily precipitation in the valley exhibits significant quasi-biweekly (10 to 20 days) oscillations. The flood-causing rainstorms in the valley were mainly associated with the confluence of low-frequency warm and humid airflow in the lower latitudes and cold and dry airflow in the higher latitudes. The low-frequency vortexes were propagating or in control when this type of rainstorms took place over the valley, being favorable for the convergence of moisture at lower levels and thus vital to the formation of the rainstorms.展开更多
Basic climatic characteristics are analyzed concerning the precipitation anomalies in raining seasons over regions south of the Changjiang River (the Yangtze). It finds that the regions are the earliest in eastern Chi...Basic climatic characteristics are analyzed concerning the precipitation anomalies in raining seasons over regions south of the Changjiang River (the Yangtze). It finds that the regions are the earliest in eastern China where raining seasons begin and end. Precipitation there tends to decrease over the past 50 years. Waters bounded by 9(S -1(S, 121(E - 129(E are the key zones of SST anomalies that affect the precipitation in these regions over May ~ July in preceding years. Long-term air-sea interactions make it possible for preceding SST anomalies to affect the general circulation that come afterwards, causing precipitation anomalies in the raining seasons in regions south of the Changjiang River in subsequent years.展开更多
Corrosion behavior of AZ91 magnesium alloy in simulating acid rain under wet-dry cyclic condition was investigated.The results show that corrosion potential shifts positively and the corrosion current density decrease...Corrosion behavior of AZ91 magnesium alloy in simulating acid rain under wet-dry cyclic condition was investigated.The results show that corrosion potential shifts positively and the corrosion current density decreases at low wet-dry cyclic time.Further increase of the cyclic time results in the negative movement of corrosion potential and the increase of current density.SEM observation indicates that corrosion occurs only inαphase,βphase is inert in corrosive medium,and the corrosion of AZ91 magnesium appears in uniform characteristic.XPS analysis suggests that the corrosion product is mainly composed of oxide and hydroxide of magnesium and aluminum,and a small amount of sulfate is also contained in the film.展开更多
The source-receptor relation of wet deposition has been a continuous issue in studies of regional environmental pollution over the past two decades.In the absence of direct observational evidence,the problem is diffic...The source-receptor relation of wet deposition has been a continuous issue in studies of regional environmental pollution over the past two decades.In the absence of direct observational evidence,the problem is difficult to solve—a topic of broad international debate since the turn of the present century.In the present study,a variety of methods focused on the sources of the wet deposition of acidic substances,like sulfate and nitrate,were used to investigate the precipitation chemistry over the Yangtze River Delta(YRD)during 2007.Back-trajectory analysis associated with the observation data and a source tracing method coupled with the Nested Air Quality Prediction Modeling System(NAQPMS)are proved to be effective methods for investigating the sources of wet deposition over the YRD.Comparison among the back-trajectory,footprint,and NAQPMS results shows good consistency,both qualitatively and quantitatively.The most important contributor to acidic substances in the YRD,as well as heavy acid rain over the region,is the anthropogenic pollution from East China,which accounts for more than 70%.展开更多
<div style="text-align:justify;"> There are 158 sampling points to be set up in the Pearl River delta economic region. The collecting period is mostly one year, namely, from July 2007 to July 2008. The...<div style="text-align:justify;"> There are 158 sampling points to be set up in the Pearl River delta economic region. The collecting period is mostly one year, namely, from July 2007 to July 2008. The eight heavy metal elements of Cr, Ni, Cu, Pb, Zn, As, Hg, and Cd in 474 dry and wet deposition samples were tested in terms of the standard procedures. Their average annual fluxes have no obvious difference between dry deposition and wet deposition. So these elements might be at an equilibrium or quasi-equilibrium state between dry deposition and wet deposition. </div>展开更多
基金This study was supported by the ＂National Key Programme for Developing Basic Science＂ projects under Grant No. 2004CB418303the National Natural Science Foundation of China under Grant No. 40705022.
文摘Using daily outgoing long-wave radiation （OLR） data from the National Oceanic and Atmospheric Administration （NOAA） and the National Center for Environmental Prediction/National Center for Atmospheric Research （NCEP/NCAR） reanalysis data of geopotential height fields for 1979-2006, the relationship between persistent heavy rain events （PHREs） in the Huaihe River valley （HRV） and the distribution pattern of convective activity in the tropical western Pacific warm pool （WPWP） is investigated. Based on nine cases of PHREs in the HRV, common characteristics of the West Pacific subtropical high （WPSH） show that the northern edge of the WPSH continues to lie in the HRV and is associated with the persistent ＂north weak south strong＂ distribution pattern of convective activities in the WPWP. Composite analysis of OLR leading the circulation indicates that the response of the WPSH to OLR anomaly patterns lags by about 1-2 days. In order to explain the reason for the effects of the distribution pattern of convective activities in the WPWP on the persistent northern edge of the WPSH in the HRV, four typical persistent heavy and light rain events in the Yangtze River valley （YRV） are contrasted with the PHREs in the HRV. The comparison indicates that when the distribution pattern of the convective activities anomaly behaves in a weak （strong） manner across the whole WPWP, persistent heavy （light） rain tends to occur in the YRV. When the distribution pattern of the convective activities anomaly behaves according to the ＂north weak south strong＂ pattern in the WPWP, persistent heavy rain tends to occur in the HRV. The effects of the ＂north weak south strong＂ distribution pattern of convective activities on PHREs in the HRV are not obvious over the seasonal mean timescale, perhaps due to the non-extreme status of convective activities in the WPWP.
基金Chinese National Key Technology R&D Program (2009BAC51B01)National Basic Research Program "973" of China (2012CB417403)+1 种基金Meteorological Science Foundation of Jiangsu Province (KM201207)‘333’Project of Jiangsu Province and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
文摘By using NCEP/NCAR daily reanalysis data and daily precipitation data of 740 stations in China, relationships between the position variation of the West Pacific subtropical high (WPSH) and the diabatic heating during persistent and intense rains in the Yangtze-Huaihe Rivers basin are studied. The results show that the position variation of WPSH is closely associated with the diabatic heating. There are strong apparent heating sources and moisture sinks in both the basin (to the north of WPSH) and the north of Bay of Bengal (to the west of WPSH) during persistent and intense rain events. In the basin, Q 1z begins to increase 3 days ahead of intense rainfall, maximizes 2 days later and then reduces gradually, but it changes little after precipitation ends, thus preventing the WPSH from moving northward. In the north of Bay of Bengal, 2 days ahead of strong rainfall over the basin, Q 1z starts to increase and peaks 1 day after the rain occurs, leading to the westward extension of WPSH. Afterwards, Q 1z begins declining and the WPSH makes its eastward retreat accordingly. Based on the complete vertical vorticity equation, in mid-troposphere, the vertical variation of heating in the basin is favorable to the increase of cyclonic vorticity north of WPSH, which counteracts the northward movement of WPSH and favors the persistence of rainbands over the basin. The vertical variation of heating in the north of Bay of Bengal is in favor of the increase of anti-cyclonic vorticity to the west of WPSH, which induces the westward extension of WPSH.
基金supported by the National Natural Science Foundation of China[grant number 41405144]the National Key Research and Development Program of China[grant number2017YFC0210100],[grant number 2016YFD0800302],[grant number 2016YFC0201802]the Science and Technology Service Network Initiative of the Chinese Academy of Sciences[STS Plan,grant number KFJ-SW-STS-168]
文摘Atmospheric wet deposition plays an important role in the supply of nutrients and toxic substances to terrestrial and aquatic environments. Although long-term（e.g. annual, multi-year） wet deposition is recorded well, pronounced and short-term changes in precipitation chemistry are less well investigated. In the present study, the precipitation chemistry and scavenging ratio of air pollutants were observed during an extreme torrential rain event（325.6 mm at the observation site） that occurred over 19–21 July 2016 in the North China Plain（NCP）. The scavenging ratio of particles showed a similar spatial distribution to that of the precipitation amount in the NCP, indicating the efficient removal of particulate matter due to the large amount and precipitation intensity of the storm. In addition, the scavenging ratio of water soluble ions was larger than that of organics and gaseous pollutants such as SO_2 and NO_2, likely due to their differences in water solubility.Consequently, raindrops incorporated more aerosol sulfate than gaseous compounds. Due to the heavy precipitation amount, almost all species in rainwater during this storm showed their lowest concentration but the highest flux compared with other rain events, indicating an important role played by this storm in terms of the substances received by the terrestrial and marine ecosystems of the region. However, the contribution of this storm to the annual chemical flux was lower than that of precipitation amount, indicating that the atmospheric compounds were scavenged below-cloud first and were then diluted by the cloud/rainwater. Future studies are needed in the context of the occurrence of extreme rainfall events in the NCP from the perspective of climate variability.
基金Project of Science and Technology Program of Guangdong (2006B37202004)Key project of Science and Technology Program of Guangzhou (2007Z1-E0101)+2 种基金Project of Science and Technology Programof Guangdong (2009A030302012)Specialized Project for Forecasters of Promotion of New Technology of China Meteorological Administration (CMATG2007Y04)Project of Guangdong Meteorlogical Bureau(2008A02)
文摘Based on the daily precipitation data of nine stations representing the Xijiang River valley and the National Center for Environmental Prediction/National Center for Atmospheric Research (USA) reanalysis data, this study uses the wavelet analysis and band-pass filter methods to investigate the atmospheric intraseasonal oscillation characteristics of flood-causing rainstorms in the valley during the annually first raining seasons in 1968, 1994, 1998, 2002 and 2005. Results show that the daily precipitation in the valley exhibits significant quasi-biweekly (10 to 20 days) oscillations. The flood-causing rainstorms in the valley were mainly associated with the confluence of low-frequency warm and humid airflow in the lower latitudes and cold and dry airflow in the higher latitudes. The low-frequency vortexes were propagating or in control when this type of rainstorms took place over the valley, being favorable for the convergence of moisture at lower levels and thus vital to the formation of the rainstorms.
基金Interannual and Interdecadal Variation Laws Governing the Mei-yu in the Changjiang-Huanhe Rivers valley Key Foundation Project in National Natural Science Foundation (40233037) Research on the Interactions between the South Asia High and Asia Monsoon a
文摘Basic climatic characteristics are analyzed concerning the precipitation anomalies in raining seasons over regions south of the Changjiang River (the Yangtze). It finds that the regions are the earliest in eastern China where raining seasons begin and end. Precipitation there tends to decrease over the past 50 years. Waters bounded by 9(S -1(S, 121(E - 129(E are the key zones of SST anomalies that affect the precipitation in these regions over May ~ July in preceding years. Long-term air-sea interactions make it possible for preceding SST anomalies to affect the general circulation that come afterwards, causing precipitation anomalies in the raining seasons in regions south of the Changjiang River in subsequent years.
基金Project(50671005)supported by the National Natural Science Foundation of ChinaProject(2007CB613705)supported by National BasicResearch Program of China
文摘Corrosion behavior of AZ91 magnesium alloy in simulating acid rain under wet-dry cyclic condition was investigated.The results show that corrosion potential shifts positively and the corrosion current density decreases at low wet-dry cyclic time.Further increase of the cyclic time results in the negative movement of corrosion potential and the increase of current density.SEM observation indicates that corrosion occurs only inαphase,βphase is inert in corrosive medium,and the corrosion of AZ91 magnesium appears in uniform characteristic.XPS analysis suggests that the corrosion product is mainly composed of oxide and hydroxide of magnesium and aluminum,and a small amount of sulfate is also contained in the film.
基金supported by the National Natural Science Foundation of China(Grant Nos.41305113 and 41405080)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB05030203)the National Science and Technology Support Program(Grant No.2014BAC22B04)
文摘The source-receptor relation of wet deposition has been a continuous issue in studies of regional environmental pollution over the past two decades.In the absence of direct observational evidence,the problem is difficult to solve—a topic of broad international debate since the turn of the present century.In the present study,a variety of methods focused on the sources of the wet deposition of acidic substances,like sulfate and nitrate,were used to investigate the precipitation chemistry over the Yangtze River Delta(YRD)during 2007.Back-trajectory analysis associated with the observation data and a source tracing method coupled with the Nested Air Quality Prediction Modeling System(NAQPMS)are proved to be effective methods for investigating the sources of wet deposition over the YRD.Comparison among the back-trajectory,footprint,and NAQPMS results shows good consistency,both qualitatively and quantitatively.The most important contributor to acidic substances in the YRD,as well as heavy acid rain over the region,is the anthropogenic pollution from East China,which accounts for more than 70%.
文摘<div style="text-align:justify;"> There are 158 sampling points to be set up in the Pearl River delta economic region. The collecting period is mostly one year, namely, from July 2007 to July 2008. The eight heavy metal elements of Cr, Ni, Cu, Pb, Zn, As, Hg, and Cd in 474 dry and wet deposition samples were tested in terms of the standard procedures. Their average annual fluxes have no obvious difference between dry deposition and wet deposition. So these elements might be at an equilibrium or quasi-equilibrium state between dry deposition and wet deposition. </div>
