A winter onshore warm tongue extending from the Yellow Sea Warm Current to the southern Jiangsu coast, and an of fshore cold tongue extending from the southern Jiangsu coast to the southwest of Jeju Island(South Korea...A winter onshore warm tongue extending from the Yellow Sea Warm Current to the southern Jiangsu coast, and an of fshore cold tongue extending from the southern Jiangsu coast to the southwest of Jeju Island(South Korea), are newly identified based on the sea-surface temperature from satellite remote sensing, and further confirmed by the distribution of suspended sediments. In addition, there are two obvious thermal fronts associated with the onshore warm tongue and off shore cold tongue. The narrow gap between the two thermal fronts is supposed to be the pathway for the off shore transport of cold coastal water and suspended sediments. The concurrence of onshore warm and of fshore cold tongues suggests the concurrence of onshore and off shore currents in the western Yellow Sea in winter, which seems to be inconsistent with the previously accepted view that, in winter, the Yellow Sea Coastal Current flows from the Old Huanghe Delta to the southwest of Jeju Island. This distinctive phenomenon helps establish an updated view of the circulation in the western Yellow Sea in winter.展开更多
Satellite remote sensing observations show that during winter, sea surface temperature (SST) presents the structure of double warm tongues in the Huanghai Sea trough: the western and the eastern warm tongues. Numer...Satellite remote sensing observations show that during winter, sea surface temperature (SST) presents the structure of double warm tongues in the Huanghai Sea trough: the western and the eastern warm tongues. Numerical experiments based on POM are carried out to study the forming mechanism of this thermal structure and its relation to the Huanghai Sea Warm Current (HSWC). The control experiment reproduces this phenomenon quite well, and comparing experiments investigate the effect of wind and tide. It is found that the western warm tongue is mainly caused by the HSWC, which can be strengthened by wintertime southward wind. The eastern warm tongue develops under the influence of an anti-clockwise circulation which is induced by the temperature front of the Huanghai Sea Cold Water Mass (HSCWM) in summer and autumn. In the eastern portion of this circulation, the northward current carries warm water to the north, forming the eastern warm tongue, which remains till winter.展开更多
Three extreme cold events successively occurred across East Asia and North America in the 2020/21 winter.This study investigates the underlying mechanisms of these record-breaking persistent cold events from the isent...Three extreme cold events successively occurred across East Asia and North America in the 2020/21 winter.This study investigates the underlying mechanisms of these record-breaking persistent cold events from the isentropic mass circulation(IMC)perspective.Results show that the midlatitude cold surface temperature anomalies always co-occurred with the high-latitude warm anomalies,and this was closely related to the strengthening of the low-level equatorward cold air branch of the IMC,particularly along the climatological cold air routes over East Asia and North America.Specifically,the two cold surges over East Asia in early winter were results of intensification of cold air transport there,influenced by the Arctic sea ice loss in autumn.The weakened cold air transport over North America associated with warmer northeastern Pacific sea surface temperatures(SSTs)explained the concurrent anomalous warmth there.This enhanced a wavenumber-1 pattern and upward wave propagation,inducing a simultaneous and long-lasting stronger poleward warm air branch(WB)of the IMC in the stratosphere and hence a displacement-type Stratospheric Sudden Warming(SSW)event on 4 January.The WB-induced increase in the air mass transported into the polar stratosphere was followed by intensification of the equatorward cold branch,hence promoting the occurrence of two extreme cold events respectively over East Asia in the beginning of January and over North America in February.Results do not yield a robust direct linkage from La Niña to the SSW event,IMC changes,and cold events,though the extratropical warm SSTs are found to contribute to the February cold surge in North America.展开更多
Effect of the spatial distributions of chlorophyll-a concentration on upper ocean temperature and currents in the equatorial Pacific is investigated through a set of numerical experiments by using an ocean general cir...Effect of the spatial distributions of chlorophyll-a concentration on upper ocean temperature and currents in the equatorial Pacific is investigated through a set of numerical experiments by using an ocean general circulation model. This study indicates that enhanced meridional gradient of chlorophyll-a between the equator and off-equatorial regions can strengthen zonal circulation and lead to a decrease in equatorial sea surface temperature (SST). However, the circulation changes by themselves are not effective enough to affect SST in the equatorial cold tongue (CT) region. The comparison between the experiments indicates that the CT SST are more sensitive to chlorophyll-a distribution away from the equator. The off-equatorial chlorophyll-a traps more solar radiation in the mixed layer, therefore, the temperature in the thermoeline decreases. The cold water can then be transported to the equator by the meridional circulation within the mixed layer. Furthermore, the relation among CT SST, the surface heat flux, and the equatorial upwelling are discussed. The study implies the simulation biases of temperature on the equator are not only related to the local ocean dynamics but also related to some deficiency in simulating off-equatorial processes.展开更多
基金Supported by the Strategy Program of Chinese Academy of Sciences(Nos.XDA10020104,XDA10020305)the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.41421005)+2 种基金the National Natural Science Foundation of China(Nos.41476019,41606040)the NSFC-Shandong Joint Fund for Marine Science Research Centers(No.U1406401)the High Performance Computing Center,Institute of Oceanology,Chinese Academy of Sciences in Qingdao
文摘A winter onshore warm tongue extending from the Yellow Sea Warm Current to the southern Jiangsu coast, and an of fshore cold tongue extending from the southern Jiangsu coast to the southwest of Jeju Island(South Korea), are newly identified based on the sea-surface temperature from satellite remote sensing, and further confirmed by the distribution of suspended sediments. In addition, there are two obvious thermal fronts associated with the onshore warm tongue and off shore cold tongue. The narrow gap between the two thermal fronts is supposed to be the pathway for the off shore transport of cold coastal water and suspended sediments. The concurrence of onshore warm and of fshore cold tongues suggests the concurrence of onshore and off shore currents in the western Yellow Sea in winter, which seems to be inconsistent with the previously accepted view that, in winter, the Yellow Sea Coastal Current flows from the Old Huanghe Delta to the southwest of Jeju Island. This distinctive phenomenon helps establish an updated view of the circulation in the western Yellow Sea in winter.
基金The National Key Basic Research Program of China under contract 2006CB403605the National Natural Science Foundation of China under contract Nos.40806016 and 40706016China 908–project under contract No. 908–02–01–03
文摘Satellite remote sensing observations show that during winter, sea surface temperature (SST) presents the structure of double warm tongues in the Huanghai Sea trough: the western and the eastern warm tongues. Numerical experiments based on POM are carried out to study the forming mechanism of this thermal structure and its relation to the Huanghai Sea Warm Current (HSWC). The control experiment reproduces this phenomenon quite well, and comparing experiments investigate the effect of wind and tide. It is found that the western warm tongue is mainly caused by the HSWC, which can be strengthened by wintertime southward wind. The eastern warm tongue develops under the influence of an anti-clockwise circulation which is induced by the temperature front of the Huanghai Sea Cold Water Mass (HSCWM) in summer and autumn. In the eastern portion of this circulation, the northward current carries warm water to the north, forming the eastern warm tongue, which remains till winter.
基金supported by grants from the National Key R&D Program of China(Grant No.2019YFC1510201)National Natural Science Foundation of China(Grant Nos.42075052 and 42088101)the Natural Science Foundation of Jiangsu Province(Grants No.BK20211288).
文摘Three extreme cold events successively occurred across East Asia and North America in the 2020/21 winter.This study investigates the underlying mechanisms of these record-breaking persistent cold events from the isentropic mass circulation(IMC)perspective.Results show that the midlatitude cold surface temperature anomalies always co-occurred with the high-latitude warm anomalies,and this was closely related to the strengthening of the low-level equatorward cold air branch of the IMC,particularly along the climatological cold air routes over East Asia and North America.Specifically,the two cold surges over East Asia in early winter were results of intensification of cold air transport there,influenced by the Arctic sea ice loss in autumn.The weakened cold air transport over North America associated with warmer northeastern Pacific sea surface temperatures(SSTs)explained the concurrent anomalous warmth there.This enhanced a wavenumber-1 pattern and upward wave propagation,inducing a simultaneous and long-lasting stronger poleward warm air branch(WB)of the IMC in the stratosphere and hence a displacement-type Stratospheric Sudden Warming(SSW)event on 4 January.The WB-induced increase in the air mass transported into the polar stratosphere was followed by intensification of the equatorward cold branch,hence promoting the occurrence of two extreme cold events respectively over East Asia in the beginning of January and over North America in February.Results do not yield a robust direct linkage from La Niña to the SSW event,IMC changes,and cold events,though the extratropical warm SSTs are found to contribute to the February cold surge in North America.
基金This study is jointly supported by the National Natural Science Foundation of China under Grant Nos.40233031,40375030,40405017,40523001 and 40775054the National Key Programme 2006CB403600the Chinese Academy of Sciences(CAS)International Partnership Creative Group"The Climate System Model Development and Application Studies".
文摘Effect of the spatial distributions of chlorophyll-a concentration on upper ocean temperature and currents in the equatorial Pacific is investigated through a set of numerical experiments by using an ocean general circulation model. This study indicates that enhanced meridional gradient of chlorophyll-a between the equator and off-equatorial regions can strengthen zonal circulation and lead to a decrease in equatorial sea surface temperature (SST). However, the circulation changes by themselves are not effective enough to affect SST in the equatorial cold tongue (CT) region. The comparison between the experiments indicates that the CT SST are more sensitive to chlorophyll-a distribution away from the equator. The off-equatorial chlorophyll-a traps more solar radiation in the mixed layer, therefore, the temperature in the thermoeline decreases. The cold water can then be transported to the equator by the meridional circulation within the mixed layer. Furthermore, the relation among CT SST, the surface heat flux, and the equatorial upwelling are discussed. The study implies the simulation biases of temperature on the equator are not only related to the local ocean dynamics but also related to some deficiency in simulating off-equatorial processes.