The process of air—sea fresh water exchange is included successfully in the Global— Ocean—Atmosphere Land—System model developed at the State Key Laboratory of Atmospheric Sciences and Geophysical Fluid Dynamics (...The process of air—sea fresh water exchange is included successfully in the Global— Ocean—Atmosphere Land—System model developed at the State Key Laboratory of Atmospheric Sciences and Geophysical Fluid Dynamics (LASG). The results of the coupled integration show that the climate drift has been controlled successfully. Analyses on the responses of ocean circulation to the changes of surface fresh water or salinity forcing show that the ocean spin-up stage under flux condition for salinity is the key to the implementation of air-sea fresh water flux coupling. This study also demonstrates that the Modified—Monthly—Flux—Anomaly coupling scheme (MMFA) brought forward by Yu and Zhang (1998) is suitable not only for daily air—sea heat flux coupling but also for daily fresh water flux coupling. Key words Fresh water flux - Air-sea coupling - Thermohaline circulation This work was co-supported by the National Key Project (Grant No.96-908-02-03), the Excellent National Key Laboratory Research Project (Grant No.49823002) and Chinese Academy of Sciences (CAS) under grant “ Bai Ren Ji Hua? for “Validation of Coupled Climate Models”.展开更多
The planetary boundary layer （PBL） scheme in the regional climate model （RCM） has a significant impact on the interactions and exchanges of moisture, momentum, and energy between land, ocean, and atmosphere; howev...The planetary boundary layer （PBL） scheme in the regional climate model （RCM） has a significant impact on the interactions and exchanges of moisture, momentum, and energy between land, ocean, and atmosphere; however, its uncertainty will cause large systematic biases of RCM. Based on the four different PBL schemes （YSU, ACM2, Boulac, and MYJ） in Weather Research and Forecasting （WRF） model, the impacts of these schemes on the simulation of circulation and precipitation during the East Asian summer monsoon （EASM） are investigated. The simulated results of the two local turbulent kinetic energy （TKE） schemes, Boulac and MYJ, are more consistent with the observations than those in the two nonlocal closure schemes, YSU and ACM2. The former simulate more reasonable low-level southwesterly flow over East China and west pacific subtropical high （WPSH） than the latter. As to the modeling of summer monsoon precipitation, both the spatial distributions and temporal evolutions from Boulac and MTT are also better than those in YSU and ACM2 schemes. In addition, through the comparison between YSU and Boulac experiments, the differences from the results of EASM simulation are more obvious over the oceanic area. In the experiments with the nonlocal schemes YSU and ACM2, the boundary layer mixing processes are much stronger, which lead to produce more sea surface latent heat flux and enhanced convection, and finally induce the overestimated precipitation and corresponding deviation of monsoon circulation. With the further study, it is found that the absence of air-sea interaction in WRF may amplify the biases caused by PBL scheme over the ocean. Consequently, there is a reduced latent heat flux over the sea surface and even more reasonable EASM simulation, if an ocean model coupled into WRF.展开更多
A coupling procedure of air-sea freshwater exchange in climate system models is reported in this note. The first stage of the procedure is to force OGCM to equilibrium under strong restoring surface condition on salin...A coupling procedure of air-sea freshwater exchange in climate system models is reported in this note. The first stage of the procedure is to force OGCM to equilibrium under strong restoring surface condition on salinity, then increase the relaxing coefficient and get another steady state. The second stage is to switch the forcing on salinity from the weak restoring condition to the flux condition, and then finish a long-term spinning-up integration. After finishing these OGCM spinning-up stages, the last stage is to couple the OGCM with an active atmosphere, i.e. AGCM. Verification with the Global-Ocean-Atmosphere-Land-System model developed at the State Key Laboratory of Atmospheric Sciences and Geophysical Fluid Dynamics (LASG) shows that the preferred procedure is successful in including the air-sea freshwater exchange process.展开更多
A severe typhoon Utor,occurring between July 3 and 8,2001,brought heavy rainfall,strong wind and storm surge.Utor was responsible for tremendous destruction and economic losses in Philippines,Taiwan and Guangdong.An a...A severe typhoon Utor,occurring between July 3 and 8,2001,brought heavy rainfall,strong wind and storm surge.Utor was responsible for tremendous destruction and economic losses in Philippines,Taiwan and Guangdong.An air-sea model system （MM5 and Princeton Ocean Model（POM））was built to simulate meteorological dynamics and ocean circulation in the South China Sea（SCS）.In the POM the output of MM5 was used as the input data.With an increased number of vertical levels,a high-resolution planetary boundary layer scheme and updated landuse/vegetation data,the accuracy of computing wind,temperature and other meteorological fields are improved in near surface and upper levels in MM5 simulations.The simulated trajectory and wind speed of Utor are close to the observed results.The simulated distribution of rainfall is accorded well with measured data in the Pearl River Delta（PRD）area.At different meteorological stations in Hong Kong,the wind,temperature and sea surface pressure are well simulated.The simulated ocean surface current and surface temperature fields have an obvious rightward-biased response to the typhoon Utor,and the maximum velocity and the lowest temperature region appear in the 30 km of the right side of the typhoon track.The typhoon Utor could make the water 50m under the surface ocean unwell to surface and the ocean surface temperature decrease by about 2°C.展开更多
The dynamical features of air-sea coupling waves and their stabilities in a simple coupled air-sea model in the tropics have been studied with respect to interaction occurring among different types of the free waves i...The dynamical features of air-sea coupling waves and their stabilities in a simple coupled air-sea model in the tropics have been studied with respect to interaction occurring among different types of the free waves in the o-cean and in the atmosphere. It is pointed out that there exist a stable and an unstable air-sea interaction modes in the tropical coupled system , respectively. The propagation of the unstable mode relies greatly on the zonal space scale, i. e. only for wave length ranging from 5 000 km to 10 000 km can the disturbance unstably move slowly eastward. The waves that slowly propagate unstably eastward agree well with the observational facts. Finally,it is also proposed that the interaction between Kelvin wave in one medium and Rossby wave in another medium is a necessary condition for the occurrence of destabilization of the coupled air-sea system in the tropics.展开更多
A numerical experiment of an asynchronous coupled ocean-atmosphere model has been described in this paper.A two-layer global atmosphere general circulation model(OSU/IAP-AGCM)and a two-layer North Pacific Ocean genera...A numerical experiment of an asynchronous coupled ocean-atmosphere model has been described in this paper.A two-layer global atmosphere general circulation model(OSU/IAP-AGCM)and a two-layer North Pacific Ocean general circulation model(NPOGCM)developed by Liu et al.(1992)are used in numerical experiment.The sea surface temperature anomaly(SSTA)corresponding to the meander of the Kuroshio is treated as the initial perturbation in the Pacific Ocean and the abnormal phenomena caused by the disturbance and the interaction between atmosphere and ocean,have been studied. The numerical experiment showed that the SST anomaly in the North Pacific could induce a new 30—60 day oscillation through the coupling between atmosphere and ocean and the interaction between the meander of the Kuroshio and atmosphere circulation is a positive feedback process.展开更多
Composite investigation is performed of global dynamic characteristics of >3—4-year period low- frequency oscillation in ENSO variability of air-sea coupling in the context of monthly mean wind and SSTA.Evidence s...Composite investigation is performed of global dynamic characteristics of >3—4-year period low- frequency oscillation in ENSO variability of air-sea coupling in the context of monthly mean wind and SSTA.Evidence suggests that the horizontal(vertical)anomaly circulation at tropical latitudes (equatorial)exhibits their evolution to be,in substance,a kind of low-frequency wave slowly travel- ling eastward,featured by wave number 2 moving along the equator and zonal wind swiftly decaying off the equator in relation to divergence/convergence:the time that the low-frequency wave takes to move around the equator in its halfway is precisely the period of the ENSO low-frequency component (LFC)(approximately 4 years);the ocean also displays corresponding response to the component.展开更多
The propagation features, stabilities and dynamical characteristic structures of coupled Kelvin inner modes and second order Rossby inner modes are studied using a simple tropical coupled air-sea model in this paper. ...The propagation features, stabilities and dynamical characteristic structures of coupled Kelvin inner modes and second order Rossby inner modes are studied using a simple tropical coupled air-sea model in this paper. It is shown that there is mechanism of selecting scale and frequency in the tropical air-sea system. The effects of air-sea coupling are mainly on the large-scale modes and nonuniform. These effects make the frequency of Kelvin modes decrease and even excite the eastward propagating Rossby inner modes. These effects make the unstable development of Kelvin modes and result in the decay of Rossby modes. The effects of atmospheric damp are opposite to those of air-sea coup- ling. The oceanic damp only make the wave amplitudes decay. Simutaneously, this paper shows the dynamical character- istic structures of air-sea coupled system and the phase relations between the atmospheric and the oceanic wave compo- nent.展开更多
The response relationship between equivalent neutral wind speed anomaly(ENWSA)and sea-air temperature difference anomaly(SATDA)has been analyzed over four typical sea regions,i.e.,the Kuroshio Extension,the Gulf Strea...The response relationship between equivalent neutral wind speed anomaly(ENWSA)and sea-air temperature difference anomaly(SATDA)has been analyzed over four typical sea regions,i.e.,the Kuroshio Extension,the Gulf Stream,the Brazil-Malvinas Confluence and the Agulhas Return Current.The results show that ENWSA is more sensitive to SATDA than sea surface temperature anomaly(SSTA),which implies that SATDA seems to be a more suitable parameter than SSTA to analyze the mesoscale air-sea interactions.Here,the slope of the linear relation between ENWSA and SATDA is defined as the air-sea coupling coefficient.It is found that the values of the coupling coefficient over the four typical sea areas have obvious seasonal variations and geographical differences.In order to reveal the reason of the seasonal variation and geographical difference of the coupling coefficient,the influences of some environmental background factors,such as the spatially averaged sea surface temperature(SST),the spatially averaged air temperature,the spatially averaged sea-air temperature difference and the spatially averaged equivalent neutral wind speed,on the coupling coefficient are discussed in detail.The results reveal that the background sea-air temperature difference is an important environmental factor which directly affects the magnitude of the coupling coefficients,meanwhile,the seasonal and geographical variations of the coupling coefficient.展开更多
Interaction between mesoscale perturbations of sea surface temperature(SSTmeso)and wind stress(WSmeso)has great influences on the ocean upwelling system and turbulent mixing in the atmospheric boundary layer.Using dai...Interaction between mesoscale perturbations of sea surface temperature(SSTmeso)and wind stress(WSmeso)has great influences on the ocean upwelling system and turbulent mixing in the atmospheric boundary layer.Using daily Quik-SCAT wind speed data and AMSR-E SST data,SSTmeso and WSmeso fields in the western coast of South America are extracted by using a locally weighted regression method(LOESS).The spatial patterns of SSTmeso and WSmeso indicate strong mesoscale SST-wind stress coupling in the region.The coupling coefficient between SSTmeso and WSmeso is about 0.0095 N/(m^2·℃)in winter and 0.0082 N/(m^2·℃)in summer.Based on mesoscale coupling relationships,the mesoscale perturbations of wind stress divergence(Div(WSmeso))and curl(Curl(WSmeso))can be obtained from the SST gradient perturbations,which can be further used to derive wind stress vector perturbations using the Tikhonov regularization method.The computational examples are presented in the western coast of South America and the patterns of the reconstructed WS meso are highly consistent with SSTmeso,but the amplitude can be underestimated significantly.By matching the spatially averaged maximum standard deviations of reconstructed WSmeso magnitude and observations,a reasonable magnitude of WSmeso can be obtained when a rescaling factor of 2.2 is used.As current ocean models forced by prescribed wind cannot adequately capture the mesoscale wind stress response,the empirical wind stress perturbation model developed in this study can be used to take into account the feedback effects of the mesoscale wind stress-SST coupling in ocean modeling.Further applications are discussed for taking into account the feedback effects of the mesoscale coupling in largescale climate models and the uncoupled ocean models.展开更多
文摘The process of air—sea fresh water exchange is included successfully in the Global— Ocean—Atmosphere Land—System model developed at the State Key Laboratory of Atmospheric Sciences and Geophysical Fluid Dynamics (LASG). The results of the coupled integration show that the climate drift has been controlled successfully. Analyses on the responses of ocean circulation to the changes of surface fresh water or salinity forcing show that the ocean spin-up stage under flux condition for salinity is the key to the implementation of air-sea fresh water flux coupling. This study also demonstrates that the Modified—Monthly—Flux—Anomaly coupling scheme (MMFA) brought forward by Yu and Zhang (1998) is suitable not only for daily air—sea heat flux coupling but also for daily fresh water flux coupling. Key words Fresh water flux - Air-sea coupling - Thermohaline circulation This work was co-supported by the National Key Project (Grant No.96-908-02-03), the Excellent National Key Laboratory Research Project (Grant No.49823002) and Chinese Academy of Sciences (CAS) under grant “ Bai Ren Ji Hua? for “Validation of Coupled Climate Models”.
基金jointly sponsored by the "Strategic Priority Research Program-Climate Change: Carbon Budget and Related Issue" of the Chinese Academy of Sciences (Grant No. XDA-05110303)the Opening Fund of Key Laboratory for Land Surface Process and Climate Change in Cold and Arid Regions, CAS, the National Basic Research Program of China (Grant No.2010CB951703)the Social Common Weal Profession Research Program of Chinese Ministry of Finance/Ministry of Science and Technology (Grant No. GYHY201006014)
文摘The planetary boundary layer （PBL） scheme in the regional climate model （RCM） has a significant impact on the interactions and exchanges of moisture, momentum, and energy between land, ocean, and atmosphere; however, its uncertainty will cause large systematic biases of RCM. Based on the four different PBL schemes （YSU, ACM2, Boulac, and MYJ） in Weather Research and Forecasting （WRF） model, the impacts of these schemes on the simulation of circulation and precipitation during the East Asian summer monsoon （EASM） are investigated. The simulated results of the two local turbulent kinetic energy （TKE） schemes, Boulac and MYJ, are more consistent with the observations than those in the two nonlocal closure schemes, YSU and ACM2. The former simulate more reasonable low-level southwesterly flow over East China and west pacific subtropical high （WPSH） than the latter. As to the modeling of summer monsoon precipitation, both the spatial distributions and temporal evolutions from Boulac and MTT are also better than those in YSU and ACM2 schemes. In addition, through the comparison between YSU and Boulac experiments, the differences from the results of EASM simulation are more obvious over the oceanic area. In the experiments with the nonlocal schemes YSU and ACM2, the boundary layer mixing processes are much stronger, which lead to produce more sea surface latent heat flux and enhanced convection, and finally induce the overestimated precipitation and corresponding deviation of monsoon circulation. With the further study, it is found that the absence of air-sea interaction in WRF may amplify the biases caused by PBL scheme over the ocean. Consequently, there is a reduced latent heat flux over the sea surface and even more reasonable EASM simulation, if an ocean model coupled into WRF.
基金This work was jointly supported by the National Key Project "Studies on the Short-Term Climate Prediction Over China" (Grant No. 96-908-02-03)and the Excellent National Key Laboratory Research Project (Grant No. 49823002).
文摘A coupling procedure of air-sea freshwater exchange in climate system models is reported in this note. The first stage of the procedure is to force OGCM to equilibrium under strong restoring surface condition on salinity, then increase the relaxing coefficient and get another steady state. The second stage is to switch the forcing on salinity from the weak restoring condition to the flux condition, and then finish a long-term spinning-up integration. After finishing these OGCM spinning-up stages, the last stage is to couple the OGCM with an active atmosphere, i.e. AGCM. Verification with the Global-Ocean-Atmosphere-Land-System model developed at the State Key Laboratory of Atmospheric Sciences and Geophysical Fluid Dynamics (LASG) shows that the preferred procedure is successful in including the air-sea freshwater exchange process.
文摘A severe typhoon Utor,occurring between July 3 and 8,2001,brought heavy rainfall,strong wind and storm surge.Utor was responsible for tremendous destruction and economic losses in Philippines,Taiwan and Guangdong.An air-sea model system （MM5 and Princeton Ocean Model（POM））was built to simulate meteorological dynamics and ocean circulation in the South China Sea（SCS）.In the POM the output of MM5 was used as the input data.With an increased number of vertical levels,a high-resolution planetary boundary layer scheme and updated landuse/vegetation data,the accuracy of computing wind,temperature and other meteorological fields are improved in near surface and upper levels in MM5 simulations.The simulated trajectory and wind speed of Utor are close to the observed results.The simulated distribution of rainfall is accorded well with measured data in the Pearl River Delta（PRD）area.At different meteorological stations in Hong Kong,the wind,temperature and sea surface pressure are well simulated.The simulated ocean surface current and surface temperature fields have an obvious rightward-biased response to the typhoon Utor,and the maximum velocity and the lowest temperature region appear in the 30 km of the right side of the typhoon track.The typhoon Utor could make the water 50m under the surface ocean unwell to surface and the ocean surface temperature decrease by about 2°C.
文摘The dynamical features of air-sea coupling waves and their stabilities in a simple coupled air-sea model in the tropics have been studied with respect to interaction occurring among different types of the free waves in the o-cean and in the atmosphere. It is pointed out that there exist a stable and an unstable air-sea interaction modes in the tropical coupled system , respectively. The propagation of the unstable mode relies greatly on the zonal space scale, i. e. only for wave length ranging from 5 000 km to 10 000 km can the disturbance unstably move slowly eastward. The waves that slowly propagate unstably eastward agree well with the observational facts. Finally,it is also proposed that the interaction between Kelvin wave in one medium and Rossby wave in another medium is a necessary condition for the occurrence of destabilization of the coupled air-sea system in the tropics.
基金The project supported by National Natural Science Foundation of China.
文摘A numerical experiment of an asynchronous coupled ocean-atmosphere model has been described in this paper.A two-layer global atmosphere general circulation model(OSU/IAP-AGCM)and a two-layer North Pacific Ocean general circulation model(NPOGCM)developed by Liu et al.(1992)are used in numerical experiment.The sea surface temperature anomaly(SSTA)corresponding to the meander of the Kuroshio is treated as the initial perturbation in the Pacific Ocean and the abnormal phenomena caused by the disturbance and the interaction between atmosphere and ocean,have been studied. The numerical experiment showed that the SST anomaly in the North Pacific could induce a new 30—60 day oscillation through the coupling between atmosphere and ocean and the interaction between the meander of the Kuroshio and atmosphere circulation is a positive feedback process.
文摘Composite investigation is performed of global dynamic characteristics of >3—4-year period low- frequency oscillation in ENSO variability of air-sea coupling in the context of monthly mean wind and SSTA.Evidence suggests that the horizontal(vertical)anomaly circulation at tropical latitudes (equatorial)exhibits their evolution to be,in substance,a kind of low-frequency wave slowly travel- ling eastward,featured by wave number 2 moving along the equator and zonal wind swiftly decaying off the equator in relation to divergence/convergence:the time that the low-frequency wave takes to move around the equator in its halfway is precisely the period of the ENSO low-frequency component (LFC)(approximately 4 years);the ocean also displays corresponding response to the component.
文摘The propagation features, stabilities and dynamical characteristic structures of coupled Kelvin inner modes and second order Rossby inner modes are studied using a simple tropical coupled air-sea model in this paper. It is shown that there is mechanism of selecting scale and frequency in the tropical air-sea system. The effects of air-sea coupling are mainly on the large-scale modes and nonuniform. These effects make the frequency of Kelvin modes decrease and even excite the eastward propagating Rossby inner modes. These effects make the unstable development of Kelvin modes and result in the decay of Rossby modes. The effects of atmospheric damp are opposite to those of air-sea coup- ling. The oceanic damp only make the wave amplitudes decay. Simutaneously, this paper shows the dynamical character- istic structures of air-sea coupled system and the phase relations between the atmospheric and the oceanic wave compo- nent.
基金The National Key Research and Development Program of China under contract No.2016YFC1401008the National Natural Science Foundation of China under contract Nos 41976167 and 41576170the National Natural Science Foundation of ChinaShandong Joint Fund for Marine Science Research Centers under contract No.U1606404.
文摘The response relationship between equivalent neutral wind speed anomaly(ENWSA)and sea-air temperature difference anomaly(SATDA)has been analyzed over four typical sea regions,i.e.,the Kuroshio Extension,the Gulf Stream,the Brazil-Malvinas Confluence and the Agulhas Return Current.The results show that ENWSA is more sensitive to SATDA than sea surface temperature anomaly(SSTA),which implies that SATDA seems to be a more suitable parameter than SSTA to analyze the mesoscale air-sea interactions.Here,the slope of the linear relation between ENWSA and SATDA is defined as the air-sea coupling coefficient.It is found that the values of the coupling coefficient over the four typical sea areas have obvious seasonal variations and geographical differences.In order to reveal the reason of the seasonal variation and geographical difference of the coupling coefficient,the influences of some environmental background factors,such as the spatially averaged sea surface temperature(SST),the spatially averaged air temperature,the spatially averaged sea-air temperature difference and the spatially averaged equivalent neutral wind speed,on the coupling coefficient are discussed in detail.The results reveal that the background sea-air temperature difference is an important environmental factor which directly affects the magnitude of the coupling coefficients,meanwhile,the seasonal and geographical variations of the coupling coefficient.
基金Supported by the National Key Research and Development Program of China(No.2017YFC1404102(2017YFC1404100))the National Program on Global Change and Air-sea Interaction(No.GASI-IPOVAI-06)+3 种基金the National Natural Science Foundation of China(Nos.41490644(41490640),41690122(41690120))the Chinese Academy of Sciences Strategic Priority Project(No.XDA19060102)the NSFC Shandong Joint Fund for Marine Science Research Centers(No.U1406402)the Taishan Scholarship and the Recruitment Program of Global Experts。
文摘Interaction between mesoscale perturbations of sea surface temperature(SSTmeso)and wind stress(WSmeso)has great influences on the ocean upwelling system and turbulent mixing in the atmospheric boundary layer.Using daily Quik-SCAT wind speed data and AMSR-E SST data,SSTmeso and WSmeso fields in the western coast of South America are extracted by using a locally weighted regression method(LOESS).The spatial patterns of SSTmeso and WSmeso indicate strong mesoscale SST-wind stress coupling in the region.The coupling coefficient between SSTmeso and WSmeso is about 0.0095 N/(m^2·℃)in winter and 0.0082 N/(m^2·℃)in summer.Based on mesoscale coupling relationships,the mesoscale perturbations of wind stress divergence(Div(WSmeso))and curl(Curl(WSmeso))can be obtained from the SST gradient perturbations,which can be further used to derive wind stress vector perturbations using the Tikhonov regularization method.The computational examples are presented in the western coast of South America and the patterns of the reconstructed WS meso are highly consistent with SSTmeso,but the amplitude can be underestimated significantly.By matching the spatially averaged maximum standard deviations of reconstructed WSmeso magnitude and observations,a reasonable magnitude of WSmeso can be obtained when a rescaling factor of 2.2 is used.As current ocean models forced by prescribed wind cannot adequately capture the mesoscale wind stress response,the empirical wind stress perturbation model developed in this study can be used to take into account the feedback effects of the mesoscale wind stress-SST coupling in ocean modeling.Further applications are discussed for taking into account the feedback effects of the mesoscale coupling in largescale climate models and the uncoupled ocean models.
