According to the national standard(2006)on tropical cyclone(TC)intensity,TCs are categorized into six intensity types,namely,tropical depression(TD),tropical storm(TS),severe tropical storm(STS), typhoon(TY),severe ty...According to the national standard(2006)on tropical cyclone(TC)intensity,TCs are categorized into six intensity types,namely,tropical depression(TD),tropical storm(TS),severe tropical storm(STS), typhoon(TY),severe typhoon(STY),and super severe typhoon(SSTY).Fifty-eight years(1949–2006)of the datasets from the Yearbook of Typhoons and Yearbook of Tropical Cyclones were used to study the variation characteristics of TCs making landfalls in China's Mainland,Hainan and Taiwan islands.The main results are as follows.First,interannual or interdecadal variations in the number of landfalling TCs at different intensities exist.As far as long-term trends are concerned,the TD and TS frequencies show a significant linearly decreasing trend while those of STY show a significant linearly increasing trend.Second, a significant period of 6–8 years exist in the variations of annual landfalling TD,TS,and STS frequencies while quasi-16-year periods are found in the annual TY frequency.Third,TD and TS are generated mostly over the South China Sea,while TY,STY,and SSTY mostly over the waters southeast of the Bashi Channel and the ocean to the east of the Philippines.Fourth,as far as interdecadal trends are concerned,the frequencies of landfalling TD and TS generated over the South China Sea show significant linearly decreasing trends.However,TY and STY show significant linearly increasing trends.展开更多
By using the data of 1949 – 2001 (53 years) of Tropical Cyclone (TC) Yearbooks, statistical analyses are performed to study the climatic features of TCs making landfall and then passing through lakes (hereafter refer...By using the data of 1949 – 2001 (53 years) of Tropical Cyclone (TC) Yearbooks, statistical analyses are performed to study the climatic features of TCs making landfall and then passing through lakes (hereafter referred to as "L-TCs") in China. Results show that L-TCs can sustain a long time over land and the intensity is very strong during the course of landfall. Lakes can noticeably slow down the reduction of TC intensity, with the minimum pressure mostly maintained or decreased and the maximum velocity increased. The middle reach of the Yangtze River has the biggest TC dissipating rate as compared with the other areas where the TC is active.展开更多
The present paper describes computational and experimental work on the vortex flow characteristics of a sharp-edged delta wing with a leading edge extension (LEX). Experiment was carried out using a low-speed wind tun...The present paper describes computational and experimental work on the vortex flow characteristics of a sharp-edged delta wing with a leading edge extension (LEX). Experiment was carried out using a low-speed wind tunnel that has a test section of 3.5 m(W)×2.45 m(H)×8.7 m(L). The angle of attack of the delta wing ranges from 10° to 30°. The free stream velocity is fixed at 20 m/s, which corresponds to Reynolds number of 0.88×106. Computations using the mass-averaged implicit 3D Navier-Stokes equations were applied to predict the complicated vortical flow over the delta wing. The governing equations were discretized in space using a fully implicit finite volume differencing formation. The standard k-e turbulent model was employed to close the governing equations. The present computations predicted the experimented flow field with a good accuracy.展开更多
基金Natural Science Foundation of China(40765002)Public Interest Research Special Foundation(meteorology)of China(200906002)
文摘According to the national standard(2006)on tropical cyclone(TC)intensity,TCs are categorized into six intensity types,namely,tropical depression(TD),tropical storm(TS),severe tropical storm(STS), typhoon(TY),severe typhoon(STY),and super severe typhoon(SSTY).Fifty-eight years(1949–2006)of the datasets from the Yearbook of Typhoons and Yearbook of Tropical Cyclones were used to study the variation characteristics of TCs making landfalls in China's Mainland,Hainan and Taiwan islands.The main results are as follows.First,interannual or interdecadal variations in the number of landfalling TCs at different intensities exist.As far as long-term trends are concerned,the TD and TS frequencies show a significant linearly decreasing trend while those of STY show a significant linearly increasing trend.Second, a significant period of 6–8 years exist in the variations of annual landfalling TD,TS,and STS frequencies while quasi-16-year periods are found in the annual TY frequency.Third,TD and TS are generated mostly over the South China Sea,while TY,STY,and SSTY mostly over the waters southeast of the Bashi Channel and the ocean to the east of the Philippines.Fourth,as far as interdecadal trends are concerned,the frequencies of landfalling TD and TS generated over the South China Sea show significant linearly decreasing trends.However,TY and STY show significant linearly increasing trends.
基金Open Foundation for Wuhan Institute of Heavy Rain, CMA (IHR2006G09)a Natural Science Foundation of China project (40575029)
文摘By using the data of 1949 – 2001 (53 years) of Tropical Cyclone (TC) Yearbooks, statistical analyses are performed to study the climatic features of TCs making landfall and then passing through lakes (hereafter referred to as "L-TCs") in China. Results show that L-TCs can sustain a long time over land and the intensity is very strong during the course of landfall. Lakes can noticeably slow down the reduction of TC intensity, with the minimum pressure mostly maintained or decreased and the maximum velocity increased. The middle reach of the Yangtze River has the biggest TC dissipating rate as compared with the other areas where the TC is active.
文摘The present paper describes computational and experimental work on the vortex flow characteristics of a sharp-edged delta wing with a leading edge extension (LEX). Experiment was carried out using a low-speed wind tunnel that has a test section of 3.5 m(W)×2.45 m(H)×8.7 m(L). The angle of attack of the delta wing ranges from 10° to 30°. The free stream velocity is fixed at 20 m/s, which corresponds to Reynolds number of 0.88×106. Computations using the mass-averaged implicit 3D Navier-Stokes equations were applied to predict the complicated vortical flow over the delta wing. The governing equations were discretized in space using a fully implicit finite volume differencing formation. The standard k-e turbulent model was employed to close the governing equations. The present computations predicted the experimented flow field with a good accuracy.
