As an approach to the technological problem that the wind data of QuikSCAT scatterometer cannot accurately describe the zone of typhoon-level strong wind speed, some objective factors such as the typhoon moving speed,...As an approach to the technological problem that the wind data of QuikSCAT scatterometer cannot accurately describe the zone of typhoon-level strong wind speed, some objective factors such as the typhoon moving speed, direction and friction are introduced in this study to construct the asymmetric strengthening of the QuikSCAT wind field. Then by adopting a technology of four-dimensional data assimilation, an experiment that includes both the assimilation and forecasting phases is designed to simulate Typhoon Rananim numerically. The results show that with model constraints and adjustment, this technology can incorporate the QuikSCAT wind data to the entire column of the model atmosphere, improve greatly the simulating effects of the whole-column wind, pressure field and the track as well as the simulated typhoon intensity covered by the forecast phase, and work positively for the forecasting of landfall locations.展开更多
Using the WRF(Weather Research Forecast)model,this work performed analysis and simulation on the rainband change during the landfall of Typhoon Haitang(2005)and found that breaking may occur over land and oceans leads...Using the WRF(Weather Research Forecast)model,this work performed analysis and simulation on the rainband change during the landfall of Typhoon Haitang(2005)and found that breaking may occur over land and oceans leads to distinct asymmetric precipitation.The breaking is related to the topographic effect as well as interactions between the typhoon and midlatitude systems at upper levels.During the landfall,divergent flows at the 200-hPa level of the South-Asian high combined with divergent flows at the periphery of the typhoon to form a weak,inverted trough in the northwest part of the storm,with the mid- and low-level divergence fields on the west and northwest side of the typhoon center maintaining steadily.It intensifies the upper-level cyclonic flows,in association with positive vorticity rotating counterclockwise together with air currents that travel stepwise into a vorticity zone in the vicinity of the typhoon core, thereby forming a vorticity transfer belt in 22–25°N that extends to the eastern part of the storm.It is right here that the high-level vorticity band is subsiding so that rainfall is prevented from developing,resulting in the rainbelt breaking,which is the principal cause of asymmetric precipitation occurrence.Migrating into its outer region,the banded vorticity of Haitang at high levels causes further amplification of the cyclonic circulation in the western part and transfer of positive vorticity into the typhoon such that the rainband breaking is more distinct.展开更多
The track of Typhoon Haitang (0505), which passed through the Taiwan Island and landed again, has been successfully simulated by using the non-hydrostatic mesoscale atmospheric model MM5. Its structure is analyzed on ...The track of Typhoon Haitang (0505), which passed through the Taiwan Island and landed again, has been successfully simulated by using the non-hydrostatic mesoscale atmospheric model MM5. Its structure is analyzed on the landing stage, and it is found that there exist good relationships between the typhoon abnormal moving track and its asymmetry structure. The effect of terrain of Taiwan Island on the typhoon Haitang, which made it rotate before landing and present a"V"type abnormal moving track in Taiwan straits, has also been simulated. Further analysis shows that the terrain of Taiwan Island not only directly affects the typhoon moving track, but also changes the typhoon track by affecting its asymmetric structure. Therefore, the typhoon asymmetric structure and the effect of terrain of Taiwan Island together results in the abnormal rotating track. The terrain of Taiwan Island tends to increase the SW-NE asymmetric structure of the typhoon and has different effect on SE-NW asymmetric structure during the landfall process of typhoon Haitang before entering and moving out of the Taiwan straits.展开更多
This study presents a new way to identify the sensitive areas,which are determined by invoking the negative anomalies of moist potential vorticity (MPV) for typhoon adaptive observations. It is found that the areas of...This study presents a new way to identify the sensitive areas,which are determined by invoking the negative anomalies of moist potential vorticity (MPV) for typhoon adaptive observations. It is found that the areas of negative MPV are the symmetric instability areas and can be taken as sensitive areas for typhoon adaptive observations. Three typhoons in 2008,Nuri,Fung-wong,and Fengshen,were simulated with the help of MM5 model. It is shown that these typhoons are well simulated in the first 12 hours. Based on these investigations,the calculations of MPV are carried out sequentially. The result shows that the negative maxima of MPV are always around the typhoon eyes for all the cases,which means that the sensitive areas are also near them all the time.展开更多
基金National Key Fundamental Research and Development Plan of China (2004CB418301)Natural Science Foundation of China (40830958)
文摘As an approach to the technological problem that the wind data of QuikSCAT scatterometer cannot accurately describe the zone of typhoon-level strong wind speed, some objective factors such as the typhoon moving speed, direction and friction are introduced in this study to construct the asymmetric strengthening of the QuikSCAT wind field. Then by adopting a technology of four-dimensional data assimilation, an experiment that includes both the assimilation and forecasting phases is designed to simulate Typhoon Rananim numerically. The results show that with model constraints and adjustment, this technology can incorporate the QuikSCAT wind data to the entire column of the model atmosphere, improve greatly the simulating effects of the whole-column wind, pressure field and the track as well as the simulated typhoon intensity covered by the forecast phase, and work positively for the forecasting of landfall locations.
基金Natural Foundamental Research and Development Project"973"Program(2009CB421503)Natural Science Foundation of China(4097503740775033)
文摘Using the WRF(Weather Research Forecast)model,this work performed analysis and simulation on the rainband change during the landfall of Typhoon Haitang(2005)and found that breaking may occur over land and oceans leads to distinct asymmetric precipitation.The breaking is related to the topographic effect as well as interactions between the typhoon and midlatitude systems at upper levels.During the landfall,divergent flows at the 200-hPa level of the South-Asian high combined with divergent flows at the periphery of the typhoon to form a weak,inverted trough in the northwest part of the storm,with the mid- and low-level divergence fields on the west and northwest side of the typhoon center maintaining steadily.It intensifies the upper-level cyclonic flows,in association with positive vorticity rotating counterclockwise together with air currents that travel stepwise into a vorticity zone in the vicinity of the typhoon core, thereby forming a vorticity transfer belt in 22–25°N that extends to the eastern part of the storm.It is right here that the high-level vorticity band is subsiding so that rainfall is prevented from developing,resulting in the rainbelt breaking,which is the principal cause of asymmetric precipitation occurrence.Migrating into its outer region,the banded vorticity of Haitang at high levels causes further amplification of the cyclonic circulation in the western part and transfer of positive vorticity into the typhoon such that the rainband breaking is more distinct.
基金Key Subsidiary Project for Meteorological Science of Wenzhou (S200601)
文摘The track of Typhoon Haitang (0505), which passed through the Taiwan Island and landed again, has been successfully simulated by using the non-hydrostatic mesoscale atmospheric model MM5. Its structure is analyzed on the landing stage, and it is found that there exist good relationships between the typhoon abnormal moving track and its asymmetry structure. The effect of terrain of Taiwan Island on the typhoon Haitang, which made it rotate before landing and present a"V"type abnormal moving track in Taiwan straits, has also been simulated. Further analysis shows that the terrain of Taiwan Island not only directly affects the typhoon moving track, but also changes the typhoon track by affecting its asymmetric structure. Therefore, the typhoon asymmetric structure and the effect of terrain of Taiwan Island together results in the abnormal rotating track. The terrain of Taiwan Island tends to increase the SW-NE asymmetric structure of the typhoon and has different effect on SE-NW asymmetric structure during the landfall process of typhoon Haitang before entering and moving out of the Taiwan straits.
基金State Key Development Program for Basic Research of China (2009CB421505)Meteorological Special Project of The Ministry of Sciences and Technology of the People’s Republic of China (GYHY200706020)+1 种基金Project of the Natural Science Foundation of China (40775031)Project of NO.2008 LASW-A01
文摘This study presents a new way to identify the sensitive areas,which are determined by invoking the negative anomalies of moist potential vorticity (MPV) for typhoon adaptive observations. It is found that the areas of negative MPV are the symmetric instability areas and can be taken as sensitive areas for typhoon adaptive observations. Three typhoons in 2008,Nuri,Fung-wong,and Fengshen,were simulated with the help of MM5 model. It is shown that these typhoons are well simulated in the first 12 hours. Based on these investigations,the calculations of MPV are carried out sequentially. The result shows that the negative maxima of MPV are always around the typhoon eyes for all the cases,which means that the sensitive areas are also near them all the time.
