A second rain belt sometimes occurs ahead of a frontal rain belt in the warm sector over coastal South China,leading to heavy precipitation.We examined the differences in the mesoscale characteristics and microphysics...A second rain belt sometimes occurs ahead of a frontal rain belt in the warm sector over coastal South China,leading to heavy precipitation.We examined the differences in the mesoscale characteristics and microphysics of the frontal and warm sector rain belts that occurred in South China on May 10–13,2022.The southern rain belt occurred in an environment with favorable mesoscale conditions but weak large-scale forcing.In contrast,the northern rain belt was related to low-level horizontal shear and the surface-level front.The interaction between the enhanced southeasterly winds and the rainfall-induced cold pool promoted the persistent growth of convection along the southern rain belt.The convective cell propagated east over the coastal area,where there was a large temperature gradient.The bow-shaped echo in this region may be closely related to the rear-inflow jet.By contrast,the initial convection of the northern rain belt was triggered along the front and the region of low-level horizontal shear,with mesoscale interactions between the enhanced warm-moist southeasterly airflow and the cold dome associated with the earlier rain.The terrain blocked the movement of the cold pool,resulting in the stagnation of the frontal convective cell at an early stage.Subsequently,a meso-γ-scale vortex formed during the rapid movement of the convective cell,corresponding to an enhancement of precipitation.The representative raindrop spectra for the southern rain belt were characterized by a greater number and higher density of raindrops than the northern rain belt,even though both resulted in comparable hourly rainfalls.These results help us better understand the characteristics of double rain belts over South China.展开更多
Upper ocean responses to the passage of sequential tropical cyclones over the northwestern South China Sea(SCS)in 2011 were investigated using satellite remote sensing data,Argo reanalysis data,and an array of mooring...Upper ocean responses to the passage of sequential tropical cyclones over the northwestern South China Sea(SCS)in 2011 were investigated using satellite remote sensing data,Argo reanalysis data,and an array of mooring data.We found that the sea surface low temperature region lasted for more than 38 days and two phytoplankton blooms occurred after the passage of sequential tropical cyclones.The upper ocean cooling reached 2–5°C with a right-side bias was observed along the typhoon track to about 200 km.The maintenance of low temperature region and the two phytoplankton blooms were mainly driven by upwelling and near-inertial turbulence mixing induced by the sequential tropical cyclones.The fi rst phytoplankton bloom appeared on the 7 th day after the passage of the three tropical cyclones,and the chlorophyll-a(chl-a)concentration increased by 226%,which may be mainly driven by typhoons induced upwelling.The second phytoplankton bloom occurred on the 30 th day,the chl-a concentration increased by 290%.Further analysis suggested that only the typhoons with similar characteristics as Nesat and Nalgae can induce strong near-inertial oscillation(NIO).Strong turbulent mixing associated with the near-inertial baroclinic shear instability lasted for 26 days.The measured mean eddy diff usivity in the upper ocean was above 10-4 m 2/s after typhoon Nesat.Enhancement of the turbulent mixing in the upper ocean helped to transport nutrient-rich cold waters from the deep layer to the euphotic layer,and is a major mechanism for the long-term maintenance of low temperature region as well as the second phytoplankton bloom.展开更多
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
Tropical Cyclones (TCs) are among the atmospheric events which may trigger/enhance the occurrence of disasters to the society in most world basins including <span style="font-family:Verdana;">the </...Tropical Cyclones (TCs) are among the atmospheric events which may trigger/enhance the occurrence of disasters to the society in most world basins including <span style="font-family:Verdana;">the </span><span style="font-family:;" "=""><span style="font-family:Verdana;">Southwestern Indian Ocean (SWIO). This study analyzed the dynamics and the impacts of the Tropical Cyclone (TC) Idai (4</span><sup><span style="font-family:Verdana;">th</span></sup><span style="font-family:Verdana;">-21</span><sup><span style="font-family:Verdana;">st</span></sup><span style="font-family:Verdana;"> March, 2019) which devastated most of the SWIO countries. The study used the Reanalysis 1 products of daily zonal (u) and meridional (v) winds, Sea Surface Temperatures (SSTs), amount of Precipitable Water (PRW), </span></span><span style="font-family:Verdana;">and relative humidity</span><span style="font-family:Verdana;"> (Rh). The dynamics and movements of Idai w</span><span style="font-family:Verdana;">ere</span><span style="font-family:Verdana;"> analyzed using the wind circulation at 850, 700, 500 and 200 mb, where the TC dynamic variables like vertical wind shear, vorticity, and the mean zonal wind were calculated using u and v components. Using the open Grid Analysis and Display System (GrADS) software the data was processed into three</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">time epochs of pre, during and post;and then analyzed to feature the state of the atmosphere before (pre), during and post TC Idai using all datasets. </span><span style="font-family:Verdana;">The </span><span style="font-family:;" "=""><span style="font-family:Verdana;">amount of precipitable water was used to map the rainfall on pre, during, and post Idai as well as during its landfall. The results revealed that dynamics of TC Idai was intensifying the weather (over Mozambique) and clearing the weather equatorward or southward of 12<span style="white-space:nowrap;">°</span>S, with low vertical wind shear ove展开更多
基金National Natural Science Foundation of China(41930972,52239006,41975001)。
文摘A second rain belt sometimes occurs ahead of a frontal rain belt in the warm sector over coastal South China,leading to heavy precipitation.We examined the differences in the mesoscale characteristics and microphysics of the frontal and warm sector rain belts that occurred in South China on May 10–13,2022.The southern rain belt occurred in an environment with favorable mesoscale conditions but weak large-scale forcing.In contrast,the northern rain belt was related to low-level horizontal shear and the surface-level front.The interaction between the enhanced southeasterly winds and the rainfall-induced cold pool promoted the persistent growth of convection along the southern rain belt.The convective cell propagated east over the coastal area,where there was a large temperature gradient.The bow-shaped echo in this region may be closely related to the rear-inflow jet.By contrast,the initial convection of the northern rain belt was triggered along the front and the region of low-level horizontal shear,with mesoscale interactions between the enhanced warm-moist southeasterly airflow and the cold dome associated with the earlier rain.The terrain blocked the movement of the cold pool,resulting in the stagnation of the frontal convective cell at an early stage.Subsequently,a meso-γ-scale vortex formed during the rapid movement of the convective cell,corresponding to an enhancement of precipitation.The representative raindrop spectra for the southern rain belt were characterized by a greater number and higher density of raindrops than the northern rain belt,even though both resulted in comparable hourly rainfalls.These results help us better understand the characteristics of double rain belts over South China.
基金Supported by the Basic Project of the Ministry of Science and Technology(No.2016YFC14001403)the National Program on Global Change and Air-Sea Interaction(No.GASI-IPOVAI-04)+1 种基金the National Science Foundation of China(Nos.41676008,40876005,U1901213)the Scientifi c Research Start-Up Foundation of Shantou University(No.NTF20006)。
文摘Upper ocean responses to the passage of sequential tropical cyclones over the northwestern South China Sea(SCS)in 2011 were investigated using satellite remote sensing data,Argo reanalysis data,and an array of mooring data.We found that the sea surface low temperature region lasted for more than 38 days and two phytoplankton blooms occurred after the passage of sequential tropical cyclones.The upper ocean cooling reached 2–5°C with a right-side bias was observed along the typhoon track to about 200 km.The maintenance of low temperature region and the two phytoplankton blooms were mainly driven by upwelling and near-inertial turbulence mixing induced by the sequential tropical cyclones.The fi rst phytoplankton bloom appeared on the 7 th day after the passage of the three tropical cyclones,and the chlorophyll-a(chl-a)concentration increased by 226%,which may be mainly driven by typhoons induced upwelling.The second phytoplankton bloom occurred on the 30 th day,the chl-a concentration increased by 290%.Further analysis suggested that only the typhoons with similar characteristics as Nesat and Nalgae can induce strong near-inertial oscillation(NIO).Strong turbulent mixing associated with the near-inertial baroclinic shear instability lasted for 26 days.The measured mean eddy diff usivity in the upper ocean was above 10-4 m 2/s after typhoon Nesat.Enhancement of the turbulent mixing in the upper ocean helped to transport nutrient-rich cold waters from the deep layer to the euphotic layer,and is a major mechanism for the long-term maintenance of low temperature region as well as the second phytoplankton bloom.
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
文摘Tropical Cyclones (TCs) are among the atmospheric events which may trigger/enhance the occurrence of disasters to the society in most world basins including <span style="font-family:Verdana;">the </span><span style="font-family:;" "=""><span style="font-family:Verdana;">Southwestern Indian Ocean (SWIO). This study analyzed the dynamics and the impacts of the Tropical Cyclone (TC) Idai (4</span><sup><span style="font-family:Verdana;">th</span></sup><span style="font-family:Verdana;">-21</span><sup><span style="font-family:Verdana;">st</span></sup><span style="font-family:Verdana;"> March, 2019) which devastated most of the SWIO countries. The study used the Reanalysis 1 products of daily zonal (u) and meridional (v) winds, Sea Surface Temperatures (SSTs), amount of Precipitable Water (PRW), </span></span><span style="font-family:Verdana;">and relative humidity</span><span style="font-family:Verdana;"> (Rh). The dynamics and movements of Idai w</span><span style="font-family:Verdana;">ere</span><span style="font-family:Verdana;"> analyzed using the wind circulation at 850, 700, 500 and 200 mb, where the TC dynamic variables like vertical wind shear, vorticity, and the mean zonal wind were calculated using u and v components. Using the open Grid Analysis and Display System (GrADS) software the data was processed into three</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">time epochs of pre, during and post;and then analyzed to feature the state of the atmosphere before (pre), during and post TC Idai using all datasets. </span><span style="font-family:Verdana;">The </span><span style="font-family:;" "=""><span style="font-family:Verdana;">amount of precipitable water was used to map the rainfall on pre, during, and post Idai as well as during its landfall. The results revealed that dynamics of TC Idai was intensifying the weather (over Mozambique) and clearing the weather equatorward or southward of 12<span style="white-space:nowrap;">°</span>S, with low vertical wind shear ove
