1 INTRODUCTION The initial state of the atmosphere is one of the key factors that affect the result of NWP. With the development of increasingly finer NWP, the quality of initial atmospheric state has been drawing mor...1 INTRODUCTION The initial state of the atmosphere is one of the key factors that affect the result of NWP. With the development of increasingly finer NWP, the quality of initial atmospheric state has been drawing more and more attention . GRAPES 3D- Var （Global and Regional Assimilation and Prediction Enhanced System , a three-dimensional variational data assimilation subsystem developed by the Chinese Academy of Atmospheric Sciences, makes a solution to the issue of NWP data vacancy in China. Owing to it, quantitative application of satellite and radar data in NWP has significant breakthroughs. With the assimilation system of GRAPES 3D-Var and GRAPES regional mesoscale model, this work compares a control and assimilation experiment with regard to a cold air surge affecting south China in late December 2004 and analyzes the sensitivity of mesoscale model forecast on initial values and the effect of initialization on the improvement of forecasting capabilities.展开更多
Using hydrographic data covering large areas of ocean for the period from June 21 to July 5 in 2009, we studied the circulation structure in the Luzon Strait area, examined the routes of water exchange between the Sou...Using hydrographic data covering large areas of ocean for the period from June 21 to July 5 in 2009, we studied the circulation structure in the Luzon Strait area, examined the routes of water exchange between the South China Sea （SCS） and the Philippine Sea, and estimated the volume transport through Luzon Strait. We found that the Kuroshio axis follows a e-shaped path slightly east of 121°E in the upper layer. With an increase in depth, the Kuroshio axis became gradually farther from the island of Luzon. To study the water exchange between the Philippine Sea and the SCS, identification of inflows and outflows is necessary. We first identified which flows contributed to the water exchange through Luzon Strait, which differs from the approach taken in previous studies. We determined that the obvious water exchange is in the section of 121°E. The westward inflow from the Philippine Sea into the SCS is 6.39 Sv in volume, and mainly in the 100-500 m layer at 19.5°-20°N （accounting for 4.40 Sv）, while the outflow from the SCS into the Philippine Sea is concentrated in the upper 100 m at 19°-20°N and upper 400 m at 21°-21.5°N, and below 240 m at 19°-19.5°N, accounting for 1.07, 3.02 and 3.43 Sv in volume transport, respectively.展开更多
Because of the importance of gravity waves （GWs） in coupling different atmospheric regions, further studies are necessary to investigate the characteristics of GW propagation in a non-isothermal atmosphere. Using a ...Because of the importance of gravity waves （GWs） in coupling different atmospheric regions, further studies are necessary to investigate the characteristics of GW propagation in a non-isothermal atmosphere. Using a nonlinear numerical model, we simulate the propagation of small amplitude GWs with various wavelengths in different non-isothermal atmospheres. Our re- sults show that the GW vertical wavelength undergoes sharp changes above the stratopause and mesopause region. Specifically for a GW with an initial vertical wavelength of 5 km, the seasonal background temperature structure difference at 50° latitude can cause the vertical wavelength to vary by -2 krn in the mesosphere and by as large as -4.5 km in the lower thermosphere. In addition, the GW paths exhibit great divergence in the height range of -65-110 kin. Our results also show that the variations of GW path, vertical wavelength and horizontal phase velocity are not synchronized in a non-isothermal atmosphere as in an isothermal atmosphere. Despite the fact that all GWs change their characteristics as they propagate upward in a non-isothermal atmosphere, the variations relative to the initial parameters at a reference height are similar for different initial vertical wavelengths. Our results indicate that the changing characteristics of a gravity wave in a non-isothermal atmosphere need to be considered when investigating the relationship of GWs at two different heights.展开更多
基金Key Scientific Research Project of Guangdong (2004B32601002)Promotion Project forLatest Meteorological Technology (CMATG2005M17)+1 种基金National Project No.973 (2004CB18307)"Research onAssimilation Techniques for Tropics based on Modern Observation Technologies"
文摘1 INTRODUCTION The initial state of the atmosphere is one of the key factors that affect the result of NWP. With the development of increasingly finer NWP, the quality of initial atmospheric state has been drawing more and more attention . GRAPES 3D- Var （Global and Regional Assimilation and Prediction Enhanced System , a three-dimensional variational data assimilation subsystem developed by the Chinese Academy of Atmospheric Sciences, makes a solution to the issue of NWP data vacancy in China. Owing to it, quantitative application of satellite and radar data in NWP has significant breakthroughs. With the assimilation system of GRAPES 3D-Var and GRAPES regional mesoscale model, this work compares a control and assimilation experiment with regard to a cold air surge affecting south China in late December 2004 and analyzes the sensitivity of mesoscale model forecast on initial values and the effect of initialization on the improvement of forecasting capabilities.
基金Supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (No. KZCX1-YW-12)the National Natural Science Foundation of China (Nos. 41030855,41006013)
文摘Using hydrographic data covering large areas of ocean for the period from June 21 to July 5 in 2009, we studied the circulation structure in the Luzon Strait area, examined the routes of water exchange between the South China Sea （SCS） and the Philippine Sea, and estimated the volume transport through Luzon Strait. We found that the Kuroshio axis follows a e-shaped path slightly east of 121°E in the upper layer. With an increase in depth, the Kuroshio axis became gradually farther from the island of Luzon. To study the water exchange between the Philippine Sea and the SCS, identification of inflows and outflows is necessary. We first identified which flows contributed to the water exchange through Luzon Strait, which differs from the approach taken in previous studies. We determined that the obvious water exchange is in the section of 121°E. The westward inflow from the Philippine Sea into the SCS is 6.39 Sv in volume, and mainly in the 100-500 m layer at 19.5°-20°N （accounting for 4.40 Sv）, while the outflow from the SCS into the Philippine Sea is concentrated in the upper 100 m at 19°-20°N and upper 400 m at 21°-21.5°N, and below 240 m at 19°-19.5°N, accounting for 1.07, 3.02 and 3.43 Sv in volume transport, respectively.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40921063, 41004063, 41074109, 40890165, and 41174127)the National Important Basic Research Project (Grant No. 2011CB811405)+3 种基金the China Postdoctoral Science Foundation (Grant No. 20100470506)supported in part by the Specialized Research Fundthe Open Research Program of the State Key Laboratory of Space Weatherthe National Science Foundation of Unites States grant-ATM-0633418 to Miami University
文摘Because of the importance of gravity waves （GWs） in coupling different atmospheric regions, further studies are necessary to investigate the characteristics of GW propagation in a non-isothermal atmosphere. Using a nonlinear numerical model, we simulate the propagation of small amplitude GWs with various wavelengths in different non-isothermal atmospheres. Our re- sults show that the GW vertical wavelength undergoes sharp changes above the stratopause and mesopause region. Specifically for a GW with an initial vertical wavelength of 5 km, the seasonal background temperature structure difference at 50° latitude can cause the vertical wavelength to vary by -2 krn in the mesosphere and by as large as -4.5 km in the lower thermosphere. In addition, the GW paths exhibit great divergence in the height range of -65-110 kin. Our results also show that the variations of GW path, vertical wavelength and horizontal phase velocity are not synchronized in a non-isothermal atmosphere as in an isothermal atmosphere. Despite the fact that all GWs change their characteristics as they propagate upward in a non-isothermal atmosphere, the variations relative to the initial parameters at a reference height are similar for different initial vertical wavelengths. Our results indicate that the changing characteristics of a gravity wave in a non-isothermal atmosphere need to be considered when investigating the relationship of GWs at two different heights.
