It is generally thought that the influence of comparable track typhoons is approximately similar, but in fact their wind and especially their rainstorm distribution are often very different. Therefore, a contrastive a...It is generally thought that the influence of comparable track typhoons is approximately similar, but in fact their wind and especially their rainstorm distribution are often very different. Therefore, a contrastive analysis of rainstorms by tropical cyclones (TCs) Haitang (0505) and Bilis (0604), which are of a similar track, is designed to help understand the mechanism of the TC rainstorm and to improve forecasting skills. The daily rainfall of TC Haitang (0505) and Bilis (0604) is diagnosed and compared. The result indicates that these two TCs have similar precipitation distribution before landfall but different precipitation characteristics after landfall. Using NCEP/GFS analysis data, the synoptic situation is analyzed; water vapor transportation is discussed regarding the calculated water vapor flux and divergence. The results show that the heavy rainfall in the Zhejiang and Fujian Provinces associated with Haitang (0505) and Bilis (0604) before landfall results from a peripheral easterly wind, a combination of the tropical cyclone and the terrain. After landfall and moving far inland of the storm, the precipitation of Haitang is caused by water vapor convergence carried by its own circulation; it is much weaker than that in the coastal area. One of the important contributing factors to heavy rainstorms in southeast Zhejiang is a southeast jet stream, which is maintained over the southeast coast. In contrast, the South China Sea monsoon circulation transports large amounts of water vapor into Bilis – when a water-vapor transport belt south of the tropical cyclone significantly strengthens – which strengthens the transport. Then, it causes water vapor flux to converge on the south side of Bilis and diverge on the north side. Precipitation is much stronger on the south side than that on the north side. After Bilis travels far inland, the cold air guided by a north trough travels into the TC and remarkably enhances precipitation. In summary, combining vertical wind shear with water vapor transportation is 展开更多
Using conventional observation data,FY2 satellite data,typhoon data and NCEP reanalysis data,the different position of Pre-TC squall line accompanying the similar tracks with"Lekima"(No.1909)and"Matsa&q...Using conventional observation data,FY2 satellite data,typhoon data and NCEP reanalysis data,the different position of Pre-TC squall line accompanying the similar tracks with"Lekima"(No.1909)and"Matsa"(No.0509)is studied.The article analyzes the circulation background and trigger mechanism generated by the two pre-TC squall lines,and uses various physical quantities such as low-level vertical wind shear,humidity,wind field,wet potential vorticity,and vertical vorticity.Also,try to study the dynamic mechanism of dry intrusion during the process using the Slantwise Vorticity Development(SVD)theory.The results show that:the high-altitude system and the ground trigger mechanism produced are significantly different.On the high-altitude system,the"Lekima"squall line is generated between the continental high pressure and the typhoon with the northeast jet.The"Matsa"squall line occurred between the typhoon and the subtropical high,and near the typhoon inverted trough,which was generated with the strong easterlies.On the ground trigger mechanism,the"Lekima"squall line is generated at the convergence line under the intersection of northeast and northwest air currents.The"Matsa"squall line is generated in the ground inverted trough moves westward and meridional degree increases.During the two pre-TC squall lines,low-level vertical wind shear values are above 16 m·s-1.The dry air intrusion in the lower layer came from the upper and middle troposphere in the vertical direction,and in the east from the west along the latitude in the horizontal direction.Theoretical analysis base on the development of wet potential vorticity,vertical vorticity,and inclined vorticity indicate that the downward transmission of the high potential vorticity band on the upper troposphere,the level of dry invasion,and the air mixing of equivalent potential temperature at high and low levels play an important role in the generation and development of the preTC squall line.The slantwise vorticity has a good corresponding relationship with the vertical展开更多
基金Plan Project of Wenzhou Science and Technology (S20080030)Open Study Special Project of Meteorological Science and Technology of Zhejiang Province (KF2008004)+1 种基金Cultivation Fund of the Key Scientific and Technical Innovation Project, Ministry of Education of China (708051)Natural Science Foundation of China (40875068)
文摘It is generally thought that the influence of comparable track typhoons is approximately similar, but in fact their wind and especially their rainstorm distribution are often very different. Therefore, a contrastive analysis of rainstorms by tropical cyclones (TCs) Haitang (0505) and Bilis (0604), which are of a similar track, is designed to help understand the mechanism of the TC rainstorm and to improve forecasting skills. The daily rainfall of TC Haitang (0505) and Bilis (0604) is diagnosed and compared. The result indicates that these two TCs have similar precipitation distribution before landfall but different precipitation characteristics after landfall. Using NCEP/GFS analysis data, the synoptic situation is analyzed; water vapor transportation is discussed regarding the calculated water vapor flux and divergence. The results show that the heavy rainfall in the Zhejiang and Fujian Provinces associated with Haitang (0505) and Bilis (0604) before landfall results from a peripheral easterly wind, a combination of the tropical cyclone and the terrain. After landfall and moving far inland of the storm, the precipitation of Haitang is caused by water vapor convergence carried by its own circulation; it is much weaker than that in the coastal area. One of the important contributing factors to heavy rainstorms in southeast Zhejiang is a southeast jet stream, which is maintained over the southeast coast. In contrast, the South China Sea monsoon circulation transports large amounts of water vapor into Bilis – when a water-vapor transport belt south of the tropical cyclone significantly strengthens – which strengthens the transport. Then, it causes water vapor flux to converge on the south side of Bilis and diverge on the north side. Precipitation is much stronger on the south side than that on the north side. After Bilis travels far inland, the cold air guided by a north trough travels into the TC and remarkably enhances precipitation. In summary, combining vertical wind shear with water vapor transportation is
基金sponsored by the China Meteorological Administration Forecaster Special Project(CMAYBY2020-062)
文摘Using conventional observation data,FY2 satellite data,typhoon data and NCEP reanalysis data,the different position of Pre-TC squall line accompanying the similar tracks with"Lekima"(No.1909)and"Matsa"(No.0509)is studied.The article analyzes the circulation background and trigger mechanism generated by the two pre-TC squall lines,and uses various physical quantities such as low-level vertical wind shear,humidity,wind field,wet potential vorticity,and vertical vorticity.Also,try to study the dynamic mechanism of dry intrusion during the process using the Slantwise Vorticity Development(SVD)theory.The results show that:the high-altitude system and the ground trigger mechanism produced are significantly different.On the high-altitude system,the"Lekima"squall line is generated between the continental high pressure and the typhoon with the northeast jet.The"Matsa"squall line occurred between the typhoon and the subtropical high,and near the typhoon inverted trough,which was generated with the strong easterlies.On the ground trigger mechanism,the"Lekima"squall line is generated at the convergence line under the intersection of northeast and northwest air currents.The"Matsa"squall line is generated in the ground inverted trough moves westward and meridional degree increases.During the two pre-TC squall lines,low-level vertical wind shear values are above 16 m·s-1.The dry air intrusion in the lower layer came from the upper and middle troposphere in the vertical direction,and in the east from the west along the latitude in the horizontal direction.Theoretical analysis base on the development of wet potential vorticity,vertical vorticity,and inclined vorticity indicate that the downward transmission of the high potential vorticity band on the upper troposphere,the level of dry invasion,and the air mixing of equivalent potential temperature at high and low levels play an important role in the generation and development of the preTC squall line.The slantwise vorticity has a good corresponding relationship with the vertical
