The generation of stratospheric gravity waves （GWs） due to typhoon is simulated by using a meso-scale model （WRF） with a typhoon case, the Matsa in 2005. An 8-day model run that covers the major stages of the Mats...The generation of stratospheric gravity waves （GWs） due to typhoon is simulated by using a meso-scale model （WRF） with a typhoon case, the Matsa in 2005. An 8-day model run that covers the major stages of the Matsa＇s development reproduces the key features of the typhoon. For example, good agreements in the typhoon＇s track, the intensity, and the spiral clouds, as well as mean state of stratosphere, are seen between the simulation results and the observation. Simulation results clearly show that with typhoon propagates northwestward, pronounced stratospheric GWs are generated continuously in the vicinity of Matsa. The GWs exhibit the typical curve-like wave fronts away from the Typhoon Matsa, and propagate preferentially in the up- stream of the background winds. These characteristics reflect that the stratospheric GWs are closely associated with the ty- phoon, and thus the GWs are referred to as Tropical Cyclone related Gravity Waves （TC-GWs）. The results also show that these waves should have a rather large horizontal scale so that the outmost wave fronts can be seen at the distance of ~ 1000 km to the typhoon center in the horizontal plane of 20 kin. This is consistent with the phenomenon of stratospheric TC-GWs with 1000 km horizontal scale disclosed by the previous observational analysis results.展开更多
The conditional nonlinear optimal perturbations（CNOPs） obtained by a fast algorithm are applied to determining the sensitive area for the targeting observation of Typhoon Matsa in 2005 using an operational regional ...The conditional nonlinear optimal perturbations（CNOPs） obtained by a fast algorithm are applied to determining the sensitive area for the targeting observation of Typhoon Matsa in 2005 using an operational regional prediction model-the Global/Regional Assimilation and PrEdiction System（GRAPES）.Through a series of sensitivity experiments,several issues on targeting strategy design are discussed,including the effectivity of different guidances to determine the sensitive area（or targeting area） and the impact of sensitive area size on improving the 24-h forecast.In this study,three guidances are used along with the CNOP to find sensitive area for improving the 24-h prediction of sea level pressure and accumulated rainfall in the verification region.The three guidances are based on winds only;on winds,geopotential height,and specific humidity;and on winds,geopotential height,specific humidity,and observation error,respectively.The distribution and effectivity of the sensitive areas are compared with each other,and the results show that the sensitive areas identified by the three guidances are different in terms of convergence and effectivity.All the sensitive areas determined by these guidances can lead to improvement of the 24-h forecast of interest. The second and third guidances are more effective and can identify more similar sensitive areas than the first one.Further,the size of sensitive areas is changed the same way for three guidances and the 24-h accumulated rainfall prediction is examined.The results suggest that a larger sensitive area can result in better prediction skill,provided that the guidance is sensitive to the size of sensitive areas.展开更多
An analysis is made to investigate the structure features of the extensive heavy rainfall left by typhoon Matsa, after its landfall in China's Mainland in August 2005, based on a range of observational results, in...An analysis is made to investigate the structure features of the extensive heavy rainfall left by typhoon Matsa, after its landfall in China's Mainland in August 2005, based on a range of observational results, including surface intensive observation data, TBB data from China's FY-2 satellite, and NCEP 1°×1° reanalysis data. The study tries to explore the interaction between atmospheric waves, 3-D atmospheric structures, and typhoon rainbands. Observational facts, diagnostic analysis, and atmospheric wave theory are used to look into the formation mechanism of distant typhoon rainbands. Results show that (1) Matsa rainbands have the features of noticeable wave train distribution and long distance propaga-tion; (2) the typhoon rainbands extend as far as 2000 km northwardly from the typhoon center, with a wavelength of 500―1000 km and a wave period of 12―24 h; (3) the wave structure of Matsa rainbands is closely associated with the corresponding wave variation of the ambient 3-D atmospheric structures, including disturbance vorticity, divergence field, vertical motion field, water vapor flux divergence field, etc. (4) both observational facts and theoretical analysis show that the northward extending typhoon rainbands are associated with the mixed effects of atmospheric inertia wave and internal gravity wave; (5) only under proper atmospheric stratification and vertical wavenumber of gravity wave, can a ty-phoon stimulate such a wave being able to reach such a distance, and result in extending wavy rain-bands.展开更多
The effects of typhoon Matsa on the ionosphere are studied by using GPS-TEC data observed at about 50 GPS stations.It is shown that the ionosphere has been already influenced and TEC tends to increase before the landi...The effects of typhoon Matsa on the ionosphere are studied by using GPS-TEC data observed at about 50 GPS stations.It is shown that the ionosphere has been already influenced and TEC tends to increase before the landing of Matsa,and the difference of TEC from its monthly median over the typhoon area is about 5 TECU.With the landing of Matsa,both the magnitude and the area of increased TEC decrease.One day after the landing of Matsa,TEC reaches its minimum and is lower than the monthly median.In comparison of TEC along the typhoon's path with that along three reference paths far from the typhoon,it is found that typhoon's impact on TEC can be fully distinguished.The evolution of TEC variation has the same tendency as reported typhoon-induced foF2.展开更多
基金supported by National Basic Research Program of China (Grant No.2010CB428603)National Natural Science Foundation of China (Grant No.40875017)Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No.KZCX2-YW-123)
文摘The generation of stratospheric gravity waves （GWs） due to typhoon is simulated by using a meso-scale model （WRF） with a typhoon case, the Matsa in 2005. An 8-day model run that covers the major stages of the Matsa＇s development reproduces the key features of the typhoon. For example, good agreements in the typhoon＇s track, the intensity, and the spiral clouds, as well as mean state of stratosphere, are seen between the simulation results and the observation. Simulation results clearly show that with typhoon propagates northwestward, pronounced stratospheric GWs are generated continuously in the vicinity of Matsa. The GWs exhibit the typical curve-like wave fronts away from the Typhoon Matsa, and propagate preferentially in the up- stream of the background winds. These characteristics reflect that the stratospheric GWs are closely associated with the ty- phoon, and thus the GWs are referred to as Tropical Cyclone related Gravity Waves （TC-GWs）. The results also show that these waves should have a rather large horizontal scale so that the outmost wave fronts can be seen at the distance of ~ 1000 km to the typhoon center in the horizontal plane of 20 kin. This is consistent with the phenomenon of stratospheric TC-GWs with 1000 km horizontal scale disclosed by the previous observational analysis results.
基金Supported by the State Key 11th Five-Year Project on Sci.& Tech.under Grant No.2006BAC02B03the China Meteorological Administration R & D Special Fund for Public Welfare(meteorology) under Grant No.GYHY(QX)2007-6-12the National Natural Science Foundation of China under Grant No.40605018
文摘The conditional nonlinear optimal perturbations（CNOPs） obtained by a fast algorithm are applied to determining the sensitive area for the targeting observation of Typhoon Matsa in 2005 using an operational regional prediction model-the Global/Regional Assimilation and PrEdiction System（GRAPES）.Through a series of sensitivity experiments,several issues on targeting strategy design are discussed,including the effectivity of different guidances to determine the sensitive area（or targeting area） and the impact of sensitive area size on improving the 24-h forecast.In this study,three guidances are used along with the CNOP to find sensitive area for improving the 24-h prediction of sea level pressure and accumulated rainfall in the verification region.The three guidances are based on winds only;on winds,geopotential height,and specific humidity;and on winds,geopotential height,specific humidity,and observation error,respectively.The distribution and effectivity of the sensitive areas are compared with each other,and the results show that the sensitive areas identified by the three guidances are different in terms of convergence and effectivity.All the sensitive areas determined by these guidances can lead to improvement of the 24-h forecast of interest. The second and third guidances are more effective and can identify more similar sensitive areas than the first one.Further,the size of sensitive areas is changed the same way for three guidances and the 24-h accumulated rainfall prediction is examined.The results suggest that a larger sensitive area can result in better prediction skill,provided that the guidance is sensitive to the size of sensitive areas.
基金Supported by the National Grand Fundamental Research 973 Program of China (Grant No. 2004CB418301)the National Natural Science Foundation of China (Grant Nos. 40675033, 40575018 and 40505009)
文摘An analysis is made to investigate the structure features of the extensive heavy rainfall left by typhoon Matsa, after its landfall in China's Mainland in August 2005, based on a range of observational results, including surface intensive observation data, TBB data from China's FY-2 satellite, and NCEP 1°×1° reanalysis data. The study tries to explore the interaction between atmospheric waves, 3-D atmospheric structures, and typhoon rainbands. Observational facts, diagnostic analysis, and atmospheric wave theory are used to look into the formation mechanism of distant typhoon rainbands. Results show that (1) Matsa rainbands have the features of noticeable wave train distribution and long distance propaga-tion; (2) the typhoon rainbands extend as far as 2000 km northwardly from the typhoon center, with a wavelength of 500―1000 km and a wave period of 12―24 h; (3) the wave structure of Matsa rainbands is closely associated with the corresponding wave variation of the ambient 3-D atmospheric structures, including disturbance vorticity, divergence field, vertical motion field, water vapor flux divergence field, etc. (4) both observational facts and theoretical analysis show that the northward extending typhoon rainbands are associated with the mixed effects of atmospheric inertia wave and internal gravity wave; (5) only under proper atmospheric stratification and vertical wavenumber of gravity wave, can a ty-phoon stimulate such a wave being able to reach such a distance, and result in extending wavy rain-bands.
基金supported by the National Natural Science Foundation of China (Grant Nos.40674077,40436015 and 40804040)Climate Change Special Foundation (Grant No.CCSF2007-12)
文摘The effects of typhoon Matsa on the ionosphere are studied by using GPS-TEC data observed at about 50 GPS stations.It is shown that the ionosphere has been already influenced and TEC tends to increase before the landing of Matsa,and the difference of TEC from its monthly median over the typhoon area is about 5 TECU.With the landing of Matsa,both the magnitude and the area of increased TEC decrease.One day after the landing of Matsa,TEC reaches its minimum and is lower than the monthly median.In comparison of TEC along the typhoon's path with that along three reference paths far from the typhoon,it is found that typhoon's impact on TEC can be fully distinguished.The evolution of TEC variation has the same tendency as reported typhoon-induced foF2.
