Meteorological conditions associated with intense rainfall and great floods over mid- and lower reaches of Yangtze River are studied by analyzing the large-, synoptic-and meso-a-scale circulation systems for 1991, 199...Meteorological conditions associated with intense rainfall and great floods over mid- and lower reaches of Yangtze River are studied by analyzing the large-, synoptic-and meso-a-scale circulation systems for 1991, 1996 and 1998. It is found that the advance and retreat of subtropical high over the West Pacific, the monsoon moisture surge from the South China Sea, cold air outbreak over mid- and high-latitudes, and the meso-α scale systems (250-2500 km) from the Tibetan Pleateau as well, are responsible for intense rainfall over the Yangtze River Valley. The persistent and heavy rains and great floods over the Yangtze River Valley occurred when all these four systems are synergetic or in phase lock.展开更多
Remarkable achievements have been made in China＇s agricultural development since the late 1970s. Nevertheless, deep-rooted problems are arising from inefficient farming practices. From mid- and long-term perspectives...Remarkable achievements have been made in China＇s agricultural development since the late 1970s. Nevertheless, deep-rooted problems are arising from inefficient farming practices. From mid- and long-term perspectives, migration of China＇s agricultural labor will slow and large-scale operation of farmland will accelerate. Although grain supply and demand have maintained a tight balance, new potentials still exist in improving grain production. Under the pressures of resource and environmental constraints, advancing the green and efficient transition of agriculture will become a new trend in China＇s agricultural development. In this context, the treatment of agricultural pollution, supply-side structural reform and innovation of agricultural subsidy policy are of strategic significance to the transition and upgrade of China＇s agriculture.展开更多
A new approach to application of mid-and low-temperature solar thermochemical technology was in-troduced and investigated.Concentrated solar thermal energy in the range of 150―300℃ can be effi-ciently converted into...A new approach to application of mid-and low-temperature solar thermochemical technology was in-troduced and investigated.Concentrated solar thermal energy in the range of 150―300℃ can be effi-ciently converted into high-grade solar fuel by integrating this technique with the endothermic reaction of hydrocarbons.The conversion mechanism of upgrading the low-grade solar thermal energy to high-grade chemical energy was examined based on the energy level.The new mechanism was used to integrate two novel solar thermal power systems:A solar/methanol fuel hybrid thermal power plant and a solar-hybrid combined cycle with inherent CO2 separation using chemical-looping combustion,for developing highly efficient solar energy use to generate electricity.An innovative prototype of a 5-kW solar receiver/reactor,as the key process for realizing the proposed system,was designed and manu-factured.Furthermore,experimental validation of energy conversion of the mid-and low-temperature solar thermochemical processes were conducted.In addition,a second practical and viable approach to the production of hydrogen,in combination with the novel mid-and low-temperature solar thermo-chemical process,was proposed and demonstrated experimentally in the manufactured solar re-ceiver/reactor prototype through methanol steam reforming.The results obtained here indicate that the development of mid-and low-temperature solar thermochemical technology may provide a promising and new direction to efficient utilization of low-grade solar thermal energy,and may enable step-wise approaches to cost-effective,globally scalable solar energy systems.展开更多
Modern oceans contain large bathymetric highs(spreading oceanic ridges,aseismic ridges or oceanic plateaus and inactive arc ridges)that,in total,constitute more than 20–30%of the total area of the world’s ocean floo...Modern oceans contain large bathymetric highs(spreading oceanic ridges,aseismic ridges or oceanic plateaus and inactive arc ridges)that,in total,constitute more than 20–30%of the total area of the world’s ocean floor.These bathymetric highs may be subducted,and such processes are commonly referred to as ridge subduction.Such ridge subduction events are not only very common and important geodynamic processes in modern oceanic plate tectonics,they also play an important role in the generation of arc magmatism,material recycling,the growth and evolution of continental crust,the deformation and modification of the overlying plates,and metallogenesis at convergent plate boundaries.Therefore,these events have attracted widespread attention.The perpendicular or high-angle subduction of mid-ocean spreading ridges is commonly characterized by the occurrence of a slab window,and the formation of a distinctive adakite–high-Mg andesite–Nb-enriched basalt-oceanic island basalt(OIB)or a mid-oceanic ridge basalt(MORB)-type rock suite,and is closely associated with Au mineralization.Aseismic ridges or oceanic plateaus are traditionally considered to be difficult to subduct,to typically collide with arcs or continents or to induce flat subduction(low angle of less than 10°)due to the thickness of their underlying normal oceanic crust(>6–7 km)and high topography.However,the subduction of aseismic ridges and oceanic plateaus occurred on both the western and eastern sides of the Pacific Ocean during the Cenozoic.On the eastern side of the Pacific Ocean,aseismic ridges or oceanic plateaus are being subducted flatly or at low angles beneath South and Central American continents,which may cause a magmatic gap.But slab melting can occur and adakites,or an adakite–high-Mg andesite–adakitic andesite–Nb-enriched basalt suite may be formed during the slab rollback or tearing.Cu-Au mineralization is commonly associated with such flat subduction events.On the western side of the Pacific Ocean,however,aseismic ridges and ocean展开更多
The impact of mid-and upper-level dry air,represented by low relative humidity(RH)values,on the genesis of tropical cyclone(TC)Durian(2001)in the South China Sea was investigated by a series of numerical experiments u...The impact of mid-and upper-level dry air,represented by low relative humidity(RH)values,on the genesis of tropical cyclone(TC)Durian(2001)in the South China Sea was investigated by a series of numerical experiments using the Weather Research and Forecasting model.The mid-level RH was lowered in different regions relative to TC Durian(2001)’s genesis location.Results suggest that the location of dry air was important to Durian(2001)’s genesis and intensification.The rapid development of the TC was accompanied by sustained near-saturated mid-and upper-level air,whereas low humidity decelerated its development.Water vapor budget analysis showed that moisture at mid and upper levels was mainly supplied by the vertical convergence of moisture flux and the divergence terms,and consumed by the condensation process.The horizontal convergence of moisture flux term supplied moisture in the air moistening process but consumed moisture in the air drying process.With a dryer mid-and upper-level environment,convective and stratiform precipitation were both inhibited.The upward mass fluxes and the diabatic heating rates associated with these two precipitation types were also suppressed.Generally,convection played the dominant role,since the impact of the stratiform process on vertical mass transportation and diabatic heating was much weaker.The vorticity budget showed that the negative vorticity convergence term,which was closely related to the inhibited convection,caused the vorticity to decrease above the lower troposphere in a dryer environment.The negative vorticity tendency is suggested to slow down the vertical coherence and the development rate of TCs.展开更多
Mid-wavelength infrared(MWIR)detection and long-wavelength infrared(LWIR)detection constitute the key technologies for space-based Earth observation and astronomical detection.The advanced ability of infrared(IR)detec...Mid-wavelength infrared(MWIR)detection and long-wavelength infrared(LWIR)detection constitute the key technologies for space-based Earth observation and astronomical detection.The advanced ability of infrared(IR)detection technology to penetrate the atmosphere and identify the camouflaged targets makes it excellent for space-based remote sensing.Thus,such detectors play an essential role in detecting and tracking low-temperature and far-distance moving targets.However,due to the diverse scenarios in which space-based IR detection systems are built,the key parameters of IR technologies are subject to unique demands.We review the developments and features of MWIR and LWIR detectors with a particular focus on their applications in space-based detection.We conduct a comprehensive analysis of key performance indicators for IR detection systems,including the ground sampling distance(GSD),operation range,and noise equivalent temperature difference(NETD)among others,and their interconnections with IR detector parameters.Additionally,the influences of pixel distance,focal plane array size,and operation temperature of space-based IR remote sensing are evaluated.The development requirements and technical challenges of MWIR and LWIR detection systems are also identified to achieve high-quality space-based observation platforms.展开更多
基金This work was supported by the National Key Basic Research Development Program (Grant Nos. G1998040908 (part 1) G1998040900 (part 2)) the Key Project of Chinese Academy of Sciences (Grant No. KZCX2-203).
文摘Meteorological conditions associated with intense rainfall and great floods over mid- and lower reaches of Yangtze River are studied by analyzing the large-, synoptic-and meso-a-scale circulation systems for 1991, 1996 and 1998. It is found that the advance and retreat of subtropical high over the West Pacific, the monsoon moisture surge from the South China Sea, cold air outbreak over mid- and high-latitudes, and the meso-α scale systems (250-2500 km) from the Tibetan Pleateau as well, are responsible for intense rainfall over the Yangtze River Valley. The persistent and heavy rains and great floods over the Yangtze River Valley occurred when all these four systems are synergetic or in phase lock.
文摘Remarkable achievements have been made in China＇s agricultural development since the late 1970s. Nevertheless, deep-rooted problems are arising from inefficient farming practices. From mid- and long-term perspectives, migration of China＇s agricultural labor will slow and large-scale operation of farmland will accelerate. Although grain supply and demand have maintained a tight balance, new potentials still exist in improving grain production. Under the pressures of resource and environmental constraints, advancing the green and efficient transition of agriculture will become a new trend in China＇s agricultural development. In this context, the treatment of agricultural pollution, supply-side structural reform and innovation of agricultural subsidy policy are of strategic significance to the transition and upgrade of China＇s agriculture.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 50836005, 50520140517 and 50506004)
文摘A new approach to application of mid-and low-temperature solar thermochemical technology was in-troduced and investigated.Concentrated solar thermal energy in the range of 150―300℃ can be effi-ciently converted into high-grade solar fuel by integrating this technique with the endothermic reaction of hydrocarbons.The conversion mechanism of upgrading the low-grade solar thermal energy to high-grade chemical energy was examined based on the energy level.The new mechanism was used to integrate two novel solar thermal power systems:A solar/methanol fuel hybrid thermal power plant and a solar-hybrid combined cycle with inherent CO2 separation using chemical-looping combustion,for developing highly efficient solar energy use to generate electricity.An innovative prototype of a 5-kW solar receiver/reactor,as the key process for realizing the proposed system,was designed and manu-factured.Furthermore,experimental validation of energy conversion of the mid-and low-temperature solar thermochemical processes were conducted.In addition,a second practical and viable approach to the production of hydrogen,in combination with the novel mid-and low-temperature solar thermo-chemical process,was proposed and demonstrated experimentally in the manufactured solar re-ceiver/reactor prototype through methanol steam reforming.The results obtained here indicate that the development of mid-and low-temperature solar thermochemical technology may provide a promising and new direction to efficient utilization of low-grade solar thermal energy,and may enable step-wise approaches to cost-effective,globally scalable solar energy systems.
基金supported by the National Natural Science Foundation of China(Grant Nos.41630208 and 91855215)the National Key R&D Program of China(Grant No.2016YFC0600407)+3 种基金the Strategic Priority Research Program(A)of the Chinese Academy of Sciences(Grant No.XDA2007030402)the Key Program of the Chinese Academy of Sciences(Grant No.QYZDJ-SSWDQC026)the Key Program of Guangzhou City(Grant No.201707020032)No.IS-2873 from GIGCAS。
文摘Modern oceans contain large bathymetric highs(spreading oceanic ridges,aseismic ridges or oceanic plateaus and inactive arc ridges)that,in total,constitute more than 20–30%of the total area of the world’s ocean floor.These bathymetric highs may be subducted,and such processes are commonly referred to as ridge subduction.Such ridge subduction events are not only very common and important geodynamic processes in modern oceanic plate tectonics,they also play an important role in the generation of arc magmatism,material recycling,the growth and evolution of continental crust,the deformation and modification of the overlying plates,and metallogenesis at convergent plate boundaries.Therefore,these events have attracted widespread attention.The perpendicular or high-angle subduction of mid-ocean spreading ridges is commonly characterized by the occurrence of a slab window,and the formation of a distinctive adakite–high-Mg andesite–Nb-enriched basalt-oceanic island basalt(OIB)or a mid-oceanic ridge basalt(MORB)-type rock suite,and is closely associated with Au mineralization.Aseismic ridges or oceanic plateaus are traditionally considered to be difficult to subduct,to typically collide with arcs or continents or to induce flat subduction(low angle of less than 10°)due to the thickness of their underlying normal oceanic crust(>6–7 km)and high topography.However,the subduction of aseismic ridges and oceanic plateaus occurred on both the western and eastern sides of the Pacific Ocean during the Cenozoic.On the eastern side of the Pacific Ocean,aseismic ridges or oceanic plateaus are being subducted flatly or at low angles beneath South and Central American continents,which may cause a magmatic gap.But slab melting can occur and adakites,or an adakite–high-Mg andesite–adakitic andesite–Nb-enriched basalt suite may be formed during the slab rollback or tearing.Cu-Au mineralization is commonly associated with such flat subduction events.On the western side of the Pacific Ocean,however,aseismic ridges and ocean
基金supported by the National Basic Research (973) Program of China (Grant No.2015CB452804)
文摘The impact of mid-and upper-level dry air,represented by low relative humidity(RH)values,on the genesis of tropical cyclone(TC)Durian(2001)in the South China Sea was investigated by a series of numerical experiments using the Weather Research and Forecasting model.The mid-level RH was lowered in different regions relative to TC Durian(2001)’s genesis location.Results suggest that the location of dry air was important to Durian(2001)’s genesis and intensification.The rapid development of the TC was accompanied by sustained near-saturated mid-and upper-level air,whereas low humidity decelerated its development.Water vapor budget analysis showed that moisture at mid and upper levels was mainly supplied by the vertical convergence of moisture flux and the divergence terms,and consumed by the condensation process.The horizontal convergence of moisture flux term supplied moisture in the air moistening process but consumed moisture in the air drying process.With a dryer mid-and upper-level environment,convective and stratiform precipitation were both inhibited.The upward mass fluxes and the diabatic heating rates associated with these two precipitation types were also suppressed.Generally,convection played the dominant role,since the impact of the stratiform process on vertical mass transportation and diabatic heating was much weaker.The vorticity budget showed that the negative vorticity convergence term,which was closely related to the inhibited convection,caused the vorticity to decrease above the lower troposphere in a dryer environment.The negative vorticity tendency is suggested to slow down the vertical coherence and the development rate of TCs.
基金Project supported by the National Basic Research Program of China(No.613322)the Beijing Nova Program,China(No.Z211100002121078)the National Natural Science Foundation of China(No.52202506)。
文摘Mid-wavelength infrared(MWIR)detection and long-wavelength infrared(LWIR)detection constitute the key technologies for space-based Earth observation and astronomical detection.The advanced ability of infrared(IR)detection technology to penetrate the atmosphere and identify the camouflaged targets makes it excellent for space-based remote sensing.Thus,such detectors play an essential role in detecting and tracking low-temperature and far-distance moving targets.However,due to the diverse scenarios in which space-based IR detection systems are built,the key parameters of IR technologies are subject to unique demands.We review the developments and features of MWIR and LWIR detectors with a particular focus on their applications in space-based detection.We conduct a comprehensive analysis of key performance indicators for IR detection systems,including the ground sampling distance(GSD),operation range,and noise equivalent temperature difference(NETD)among others,and their interconnections with IR detector parameters.Additionally,the influences of pixel distance,focal plane array size,and operation temperature of space-based IR remote sensing are evaluated.The development requirements and technical challenges of MWIR and LWIR detection systems are also identified to achieve high-quality space-based observation platforms.
