The earth we live in is a wonderful and complicated system,meteorology is a science of researching the earth and serving the public,so every country in the world is putting its attention on meteorological observation,...The earth we live in is a wonderful and complicated system,meteorology is a science of researching the earth and serving the public,so every country in the world is putting its attention on meteorological observation,and World Meteorological Organization always putting its emphasis on weather,climate展开更多
China initiated a national carbon trading market in December 2017.Commitments and actions to reduce greenhouse gas(GHG)emissions require consistent,reliable and timely information on GHG emissions.GHG monitoring and m...China initiated a national carbon trading market in December 2017.Commitments and actions to reduce greenhouse gas(GHG)emissions require consistent,reliable and timely information on GHG emissions.GHG monitoring and modeling studies provide GHG emission estimates to evaluate and guide progress towards emission reductions.GHG monitoring has mainly focused on global-scale background networks over the last few decades,while recent efforts have been made on regional and urban scales,such as projects in the Beijing-Tianjin-Hebei city cluster,in Paris,Washington-Baltimore.展开更多
To deal with the universal problem of parasitical frequency spectrum in China New Generation Weather Radar transmitter,this paper establishes mathematical models for parasitical signals existing in radar transmitters ...To deal with the universal problem of parasitical frequency spectrum in China New Generation Weather Radar transmitter,this paper establishes mathematical models for parasitical signals existing in radar transmitters and analyzes their effects on weather radar performance.Based on an engineering analysis of their possible sources,a step-by-step method to eliminate parasitical spectrum is presented,which is applied to troubleshooting experimental weather radar.Eventually,parasitical spectrum is basically eliminated.As a result,improved spectrum purity and reduced phase noise is achieved.Moreover,accuracy for velocity estimate as well as ground clutter suppression ability of the radar system is enhanced.展开更多
Year-round measurements of the mass concentration and optical properties of fine aerosols(PM_(2.5)) from June 2009 to May 2010 at an urban site in Beijing were analyzed.The annual mean values of the PM_(2.5) mass conc...Year-round measurements of the mass concentration and optical properties of fine aerosols(PM_(2.5)) from June 2009 to May 2010 at an urban site in Beijing were analyzed.The annual mean values of the PM_(2.5) mass concentration,absorption coefficient(Ab),scattering coefficient(Sc) and single scattering albedo(SSA)at 525 nm were 67±66μg/m^3,64 ±62 Mm^(-1),360 ±405 Mm^(-1) and 0.82 ±0.09,respectively.The bulk mass absorption efficiency and scattering efficiency of the PM_(2.5) at 525 nm were 0.78 m^2/g and 5.55 m^2/g,respectively.The Ab and Sc showed a similar diurnal variation with a maximum at night and a minimum in the afternoon,whereas SSA displayed an opposite diurnal pattern.Significant increases in the Ab and Sc were observed in pollution episodes caused by the accumulation of pollutants from both local and regional sources under unfavorable weather conditions.Aerosol loadings in dust events increased by several times in the spring,which had limited effects on the Ab and Sc due to the low absorption and scattering efficiency of dust particles.The frequency of haze days was the highest in autumn because of the high aerosol absorption and scattering under unfavorable weather conditions.The daily PM_(2.5)concentration should be controlled to a level lower than 64 μg/m^3 to prevent the occurrence of haze days according to its exponentially decreased relationship with visibility.展开更多
Our blue planet is made of atmosphere,hydrosphere,lithosphere and biosphere,these four layers are interdependence and interaction,which effect the environment and life on the planet.In these four layers,the hydrospher...Our blue planet is made of atmosphere,hydrosphere,lithosphere and biosphere,these four layers are interdependence and interaction,which effect the environment and life on the planet.In these four layers,the hydrosphere is mainly associated with the ocean which is crucial to the human survival and development,due to the difference heat capacities be-展开更多
Solar energy is the electromagnetic energy emitted by the sun,w hich is the dominant energy driving the Earth’s climate system[1-2],the radiation fluxes to and from the Earth’s surface are crucial to the heat econom...Solar energy is the electromagnetic energy emitted by the sun,w hich is the dominant energy driving the Earth’s climate system[1-2],the radiation fluxes to and from the Earth’s surface are crucial to the heat economy of the Earth,tiny variations in solar radiation w ill produce natural forcing of Earth’s climate w ith global-and regional-scale responses[3-4],therefore,accurate solar radiation measurements are significant for the energy balance that determines the Earth’s climate[5].M oreover,w ith global energy crisis intensifies,the utilization of solar energy resource has been putting on more and more展开更多
Given that horizontal wind plays an important role in predicting the trajectory of the manned spacecraft SHENZHOU-7 when employing a parachute, the China Meteorological Administration conducted an experiment involving...Given that horizontal wind plays an important role in predicting the trajectory of the manned spacecraft SHENZHOU-7 when employing a parachute, the China Meteorological Administration conducted an experiment involving high-resolution wind ob servation, analysis and prediction between September 21 and 28, 2008. In this work, an algorithm for tracking a spacecraft de ploying a parachute is studied. High-resolution wind profiles obtained from a numerical weather model, upper-atmosphere soundings and mobile incoherent Doppler wind lidar are compared. Forward and backward trajectory predictions based on various wind profiles, as well as their differences, are presented. In addition, the trajectory of SHENZHOU-7 is predicted using different wind profiles, and the predicted parachute-opening and landing points are compared with the observed points. Results indicate that a high-resolution numerical weather model and fine observation data can offer more-detailed wind information for the prediction of spacecraft trajectories and can thus help in the editing and sending of flight commands, consequently increas ing the accuracy and reliability of landing on an assigned spot and reducing the search area and rescue time.展开更多
文摘The earth we live in is a wonderful and complicated system,meteorology is a science of researching the earth and serving the public,so every country in the world is putting its attention on meteorological observation,and World Meteorological Organization always putting its emphasis on weather,climate
文摘China initiated a national carbon trading market in December 2017.Commitments and actions to reduce greenhouse gas(GHG)emissions require consistent,reliable and timely information on GHG emissions.GHG monitoring and modeling studies provide GHG emission estimates to evaluate and guide progress towards emission reductions.GHG monitoring has mainly focused on global-scale background networks over the last few decades,while recent efforts have been made on regional and urban scales,such as projects in the Beijing-Tianjin-Hebei city cluster,in Paris,Washington-Baltimore.
基金supported by the National Natural Science Foundation of China (40975018)the Meteorological Observation Centre of China Meteorological Administration
文摘To deal with the universal problem of parasitical frequency spectrum in China New Generation Weather Radar transmitter,this paper establishes mathematical models for parasitical signals existing in radar transmitters and analyzes their effects on weather radar performance.Based on an engineering analysis of their possible sources,a step-by-step method to eliminate parasitical spectrum is presented,which is applied to troubleshooting experimental weather radar.Eventually,parasitical spectrum is basically eliminated.As a result,improved spectrum purity and reduced phase noise is achieved.Moreover,accuracy for velocity estimate as well as ground clutter suppression ability of the radar system is enhanced.
基金supported by the National Basic Research Program of China(2014CB441202)the National Natural Science Foundation of China(Nos.41175131 and 41305128)the Special Scientific Research Funds for Environment Protection Commonweal Section(No.201409027)
文摘Year-round measurements of the mass concentration and optical properties of fine aerosols(PM_(2.5)) from June 2009 to May 2010 at an urban site in Beijing were analyzed.The annual mean values of the PM_(2.5) mass concentration,absorption coefficient(Ab),scattering coefficient(Sc) and single scattering albedo(SSA)at 525 nm were 67±66μg/m^3,64 ±62 Mm^(-1),360 ±405 Mm^(-1) and 0.82 ±0.09,respectively.The bulk mass absorption efficiency and scattering efficiency of the PM_(2.5) at 525 nm were 0.78 m^2/g and 5.55 m^2/g,respectively.The Ab and Sc showed a similar diurnal variation with a maximum at night and a minimum in the afternoon,whereas SSA displayed an opposite diurnal pattern.Significant increases in the Ab and Sc were observed in pollution episodes caused by the accumulation of pollutants from both local and regional sources under unfavorable weather conditions.Aerosol loadings in dust events increased by several times in the spring,which had limited effects on the Ab and Sc due to the low absorption and scattering efficiency of dust particles.The frequency of haze days was the highest in autumn because of the high aerosol absorption and scattering under unfavorable weather conditions.The daily PM_(2.5)concentration should be controlled to a level lower than 64 μg/m^3 to prevent the occurrence of haze days according to its exponentially decreased relationship with visibility.
基金This work was supported by the National Key R&D Program of China[grant number 2017YFB0504000]the National Natural Science Foundation of China[grant numbers 41705113 and 41877312].
文摘Our blue planet is made of atmosphere,hydrosphere,lithosphere and biosphere,these four layers are interdependence and interaction,which effect the environment and life on the planet.In these four layers,the hydrosphere is mainly associated with the ocean which is crucial to the human survival and development,due to the difference heat capacities be-
文摘Solar energy is the electromagnetic energy emitted by the sun,w hich is the dominant energy driving the Earth’s climate system[1-2],the radiation fluxes to and from the Earth’s surface are crucial to the heat economy of the Earth,tiny variations in solar radiation w ill produce natural forcing of Earth’s climate w ith global-and regional-scale responses[3-4],therefore,accurate solar radiation measurements are significant for the energy balance that determines the Earth’s climate[5].M oreover,w ith global energy crisis intensifies,the utilization of solar energy resource has been putting on more and more
文摘Given that horizontal wind plays an important role in predicting the trajectory of the manned spacecraft SHENZHOU-7 when employing a parachute, the China Meteorological Administration conducted an experiment involving high-resolution wind ob servation, analysis and prediction between September 21 and 28, 2008. In this work, an algorithm for tracking a spacecraft de ploying a parachute is studied. High-resolution wind profiles obtained from a numerical weather model, upper-atmosphere soundings and mobile incoherent Doppler wind lidar are compared. Forward and backward trajectory predictions based on various wind profiles, as well as their differences, are presented. In addition, the trajectory of SHENZHOU-7 is predicted using different wind profiles, and the predicted parachute-opening and landing points are compared with the observed points. Results indicate that a high-resolution numerical weather model and fine observation data can offer more-detailed wind information for the prediction of spacecraft trajectories and can thus help in the editing and sending of flight commands, consequently increas ing the accuracy and reliability of landing on an assigned spot and reducing the search area and rescue time.
