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
本文推导出柱坐标系下含有粘性摩擦项的正压方程组。选取2005年台风麦莎登陆浙江过程中的8月6日15时的WRF(Weather Research and Forecasting)模式输出资料,利用数值差分方法对该正压方程组求特征波解,分析粘性摩擦对台风麦莎内部正压...本文推导出柱坐标系下含有粘性摩擦项的正压方程组。选取2005年台风麦莎登陆浙江过程中的8月6日15时的WRF(Weather Research and Forecasting)模式输出资料,利用数值差分方法对该正压方程组求特征波解,分析粘性摩擦对台风麦莎内部正压特征波动的影响。结果表明,重力惯性外波在粘性摩擦的影响下,最不稳定波的波数为45左右,波动在摩擦的影响下衰减,波动沿逆时针传播,在半径1000 km处,1波波速为47.43 m/s,在半径r】800 km的范围内,径向风分量扰动加大,辐合辐散运动增强;而摩擦影响下的涡旋Rossby波,2波最不稳定,波动增长率减小,在半径r=200 km处波动相速度为4.282~29.172 m/s,扰动涡度大值区范围减小,涡旋Rossby波的波动区域沿着径向向台风中心收缩。分析包含所有波动时,考虑摩擦后,最不稳定波数在45左右且波动衰减,1波波速在r=1000 km处(外螺旋雨带)为26.374 m/s;在半径r=200 km(内螺旋雨带)为5.275 m/s,考虑径向基本气流后,最不稳定波的波数保持不变,半径r=1000 km处的波速增加为30.324 m/s,r=200 km(内螺旋雨带)处波速为6.065 m/s,摩擦使得径向风分量扰动明显增大,辐合辐散运动加强。展开更多
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.
