Satellite observations provide large amount of information of clouds and precipitation and play an important role in the forecast of heavy rainfall.However,we have not fully taken advantage of satellite observations i...Satellite observations provide large amount of information of clouds and precipitation and play an important role in the forecast of heavy rainfall.However,we have not fully taken advantage of satellite observations in the data assimilation of numerical weather predictions,especially those in infrared channels. It is common to only assimilate radiances under clear-sky conditions since it is extremely difficult to simulate infrared transmittance in cloudy sky.On the basis of the Global and Regional Assimilation and Prediction Enhanced System 3-dimensional variance(GRAPES-3DVar),cloud liquid water content, ice-water content and cloud cover are employed as governing variables in the assimilation system.This scheme can improve the simulation of infrared transmittance by a fast radiative transfer model for TOVS (RTTOV)and adjust the atmospheric and cloud parameters based on infrared radiance observations.In this paper,we investigate a heavy rainfall over Guangdong province on May 26,2007,which is right after the onset of a South China Sea monsoon.In this case,channels of the Moderate Resolution Imaging Spectroradiometer(MODIS)for observing water vapor(Channel 27)and cloud top altitude(Channel 36)are selected for the assimilation.The process of heavy rainfall is simulated by the Weather Research and Forecasting(WRF)model.Our results show that the assimilated MODIS data can improve the distribution of water vapor and temperature in the first guess field and indirectly adjust the upper-level wind field.The tendency of adjustment agrees well with the satellite observations.The assimilation scheme has positive impacts on the short-range forecasting of rainstorm.展开更多
Many kinds of high temperature superconductor （HTS） power machines such as HTS cable, HTS fault current limitcr and HTS magnet are cooled by liquid nitrogen. The level of liquid nitrogen should be monitored and cont...Many kinds of high temperature superconductor （HTS） power machines such as HTS cable, HTS fault current limitcr and HTS magnet are cooled by liquid nitrogen. The level of liquid nitrogen should be monitored and controlled to ensure the thermal stability and the dielectric strength as well. To measure the level, capacitance method and differential pressure method are usually used. However, each method has installation difficulties and measurement errors for unsteady state operation with varying system pressure. A new liquid level meter using a 2G HTS conductor is described, which has similar structure with the liquid helium level meter with NbTi filament. The level meter is fabricated with a parallel connected heater, which helps the separation of the superconducting region and normal region, considering the critical temperature, large heat capacity of conductor and cooling characteristics. The level of liquid nitrogen can be obtained from the measured voltage signal along the 2G HTS conductor. Design, fabrication and test results of the new liquid nitrogen level meter are presented.展开更多
The weather system, meteorological conditions, and microphysics of cloud, fog, and rain droplets are studied during the formation, growth, maintenance, and shedding periods of ice accretion on wires in Enshi, Hubei Pr...The weather system, meteorological conditions, and microphysics of cloud, fog, and rain droplets are studied during the formation, growth, maintenance, and shedding periods of ice accretion on wires in Enshi, Hubei Province in China using 2008/2009 and 2009/2010 winter observations. The comprehensive observations include data of visibility, microphysics of fog and rain droplets, and ice thickness, as well as data from an automated weather station and other routinely recorded meteorological data. The results show that icing occurred during the passage of a cold front, with a high-pressure system and a cold temperature trough at 850 hPa, and a southeasterly at 500 hPa that provided abundant moisture. Ice formation usually started in the evening or early morning, and ice shed around noon the following day when the temperature was -1℃ to 0℃. The averaged liquid water content of the fog droplet was distinctly greater during the growth period than during the other three periods, and there was precipitation during the growth period in each case of ice accretion. The growth rate of the ice thickness was clearly correlated with the liquid water content, with a correlation coefficient of 0.62. Simulations using empirical equations were carried out, and the simulated ice thickness agreed with observations fairly well.展开更多
基金Natural Foundamental Research and Development Project"973"Program(2009CB421500)Natural Science Foundation of China(7035011)
文摘Satellite observations provide large amount of information of clouds and precipitation and play an important role in the forecast of heavy rainfall.However,we have not fully taken advantage of satellite observations in the data assimilation of numerical weather predictions,especially those in infrared channels. It is common to only assimilate radiances under clear-sky conditions since it is extremely difficult to simulate infrared transmittance in cloudy sky.On the basis of the Global and Regional Assimilation and Prediction Enhanced System 3-dimensional variance(GRAPES-3DVar),cloud liquid water content, ice-water content and cloud cover are employed as governing variables in the assimilation system.This scheme can improve the simulation of infrared transmittance by a fast radiative transfer model for TOVS (RTTOV)and adjust the atmospheric and cloud parameters based on infrared radiance observations.In this paper,we investigate a heavy rainfall over Guangdong province on May 26,2007,which is right after the onset of a South China Sea monsoon.In this case,channels of the Moderate Resolution Imaging Spectroradiometer(MODIS)for observing water vapor(Channel 27)and cloud top altitude(Channel 36)are selected for the assimilation.The process of heavy rainfall is simulated by the Weather Research and Forecasting(WRF)model.Our results show that the assimilated MODIS data can improve the distribution of water vapor and temperature in the first guess field and indirectly adjust the upper-level wind field.The tendency of adjustment agrees well with the satellite observations.The assimilation scheme has positive impacts on the short-range forecasting of rainstorm.
基金Project supported by the Second Stage of Brain Korea 21 Projects
文摘Many kinds of high temperature superconductor （HTS） power machines such as HTS cable, HTS fault current limitcr and HTS magnet are cooled by liquid nitrogen. The level of liquid nitrogen should be monitored and controlled to ensure the thermal stability and the dielectric strength as well. To measure the level, capacitance method and differential pressure method are usually used. However, each method has installation difficulties and measurement errors for unsteady state operation with varying system pressure. A new liquid level meter using a 2G HTS conductor is described, which has similar structure with the liquid helium level meter with NbTi filament. The level meter is fabricated with a parallel connected heater, which helps the separation of the superconducting region and normal region, considering the critical temperature, large heat capacity of conductor and cooling characteristics. The level of liquid nitrogen can be obtained from the measured voltage signal along the 2G HTS conductor. Design, fabrication and test results of the new liquid nitrogen level meter are presented.
基金supported by National Key Technology R&D Program of China (Grant No. 2008BAC48B01)National Natural Science Foundation of China (Grant No. 40775012)+1 种基金the Jiangsu Province Qinglan Project for Cloud Fog Precipitation and the Aerosol Research Groupa project funded by the Priority Acadenic Program Development of Jiangsu Higher Education Institutions
文摘The weather system, meteorological conditions, and microphysics of cloud, fog, and rain droplets are studied during the formation, growth, maintenance, and shedding periods of ice accretion on wires in Enshi, Hubei Province in China using 2008/2009 and 2009/2010 winter observations. The comprehensive observations include data of visibility, microphysics of fog and rain droplets, and ice thickness, as well as data from an automated weather station and other routinely recorded meteorological data. The results show that icing occurred during the passage of a cold front, with a high-pressure system and a cold temperature trough at 850 hPa, and a southeasterly at 500 hPa that provided abundant moisture. Ice formation usually started in the evening or early morning, and ice shed around noon the following day when the temperature was -1℃ to 0℃. The averaged liquid water content of the fog droplet was distinctly greater during the growth period than during the other three periods, and there was precipitation during the growth period in each case of ice accretion. The growth rate of the ice thickness was clearly correlated with the liquid water content, with a correlation coefficient of 0.62. Simulations using empirical equations were carried out, and the simulated ice thickness agreed with observations fairly well.
