The effect of Stokes drift production(SDP),which includes Coriolis-Stokes forcing,Langmuir circulation,and Craik-Lei-bovich vortexes,on the upper ocean during typhoon passage in the Bohai Sea(BS),China,is investigated...The effect of Stokes drift production(SDP),which includes Coriolis-Stokes forcing,Langmuir circulation,and Craik-Lei-bovich vortexes,on the upper ocean during typhoon passage in the Bohai Sea(BS),China,is investigated by using a coupled wave-current model.The role of SDP in turbulent mixing and the further dynamics during the entire typhoon period are comprehensively stud-ied.Experimental results show that SDP greatly increases turbulent mixing at all depths under typhoon conditions by up to seven times that under normal weather conditions.SDP generally strengthens sea surface cooling by more than 0.4℃,with the maximum reduction in sea surface temperature(SST)at the during-typhoon stage exceeding 2℃,which is approximately seven times larger than that under normal weather conditions.The SDP-induced decrease in current speed can exceed 0.2ms^(-1),and the change in current direction is generally opposite the wind direction.These results suggest that Stokes drift depresses the effect of strong winds on currents by intensifying turbulent mixing.Mixed layer depth(MLD)is distinctly increased by O(1)during typhoons due to SDP and can deepen by more than 5m.In addition,the continuous effects of SDP on SST,current,and MLD at the after-typhoon stage indi-cate a hysteretic response between SDP and typhoon actions.展开更多
The SAR（Synthetic Aperture Radar） has the capabilities for all-weather day and night use. In the case of determining the effects of oil spill dumping, the oil spills areas are shown as dark spots in the SAR images.T...The SAR（Synthetic Aperture Radar） has the capabilities for all-weather day and night use. In the case of determining the effects of oil spill dumping, the oil spills areas are shown as dark spots in the SAR images.Therefore, using SAR data to detect oil spills is becoming progressively popular in operational monitoring, which is useful for oceanic environmental protection and hazard reduction. Research has been conducted on the polarization decomposition and scattering characteristics of oil spills from a scattering matrix using allpolarization of the SAR data, calculation of the polarization parameters, and utilization of the CPD（Co-polarized Phase Difference） of the oil and the sea, in order to extract the oil spill information. This method proves to be effective by combining polarization parameters with the characteristics of oil spill. The results show that when using Bragg, the oil spill backscattering machine with Enopy and a mean scatter α parameter. The oil spill can be successfully identified. However, the parameter mechanism of the oil spill remains unclear. The use of CPD can easily extract oil spill information from the ocean, and the polarization research provides a base for oil spill remote sensing detection.展开更多
The northern edge of the East Asian summer monsoon （EASM） is identified using the pentad total column water vapor obtained from ERA-Interim reanalysis data during 1979-2015.Empirical orthogonal function analysis is ...The northern edge of the East Asian summer monsoon （EASM） is identified using the pentad total column water vapor obtained from ERA-Interim reanalysis data during 1979-2015.Empirical orthogonal function analysis is applied to study the meridional displacement of the northern edge of the EASM during the study period,and the results show an interdecadal southward shift around 1993/1994 and an indistinct northward displacement after 2007/2008.To focus on the interdecadal change around 1993/1994,composite analysis using the difference between 1979-1993 and 1994-2007 is employed.Through examination of the differences between these two periods,a significant anticyclonic anomaly is found over Mongolia,suggesting a pronounced interdecadal weakening of the Mongolian low during 1994-2007.Thus,northward advancement of the EASM may have been prevented by the anomalous northerly flow to the east of the weakened Mongolian low after 1993.Further study shows that the interdecadal weakening of the Mongolian low might be attributable to the meridional inhomogeneity of surface warming over the northern part of East Asia.Previous studies suggest that such meridional inhomogeneity would lead to a reduction in local atmospheric baroclinicity,and thus the suppression of extratropical cyclone activity over Mongolia,resulting in a southward withdrawal of the northern edge of the EASM on the interdecadal timescale.展开更多
In order to explore the interaction be- tween the sea and monsoon in the South China Sea, the heat exchanges at air-sea interface during mon- soon periods in 1986 were calculated using observa- tional data. It shows t...In order to explore the interaction be- tween the sea and monsoon in the South China Sea, the heat exchanges at air-sea interface during mon- soon periods in 1986 were calculated using observa- tional data. It shows that when the summer monsoon bursts and prevails over the South China Sea, the air-sea interface heat exchange is strong and the latent heat rises rapidly in the intertropical conver- gence zone and the tropic cyclone system near 20.49°N, 114.14°E. On May 24, 1986, the sensible heat became positive in the typhoon system. The heating exchange indicates that heat is transported from ocean to atmosphere, with major contribution of latent heat. When the summer monsoon prevails over the South China Sea and the weather is fine, even SST (sea surface temperature) is high, but sensible heat appears to be negative. The heat exchange indicates that heat is transported from atmosphere to ocean, with major contribution of short-wave radiation absorbed by sea surface and sensible heat. When summer monsoon is over and the northeast monsoon prevails over the South China Sea, the heat ex- change at air-sea interface is very strong. The heat- ing exchange shows that the ocean heats the at- mosphere, with major contribution of latent heat when cold air arrives at the sea surface and the sensible heat rises to positive rapidly. Therefore it can be concluded that the heat exchange at air-sea interface is different from the SST in South China Sea. Whenthe summer monsoon prevails over the South China Sea, the main trend is the ocean responding to the atmosphere.展开更多
After the approach by Mellor （2003, 2008）, the present paper reports on a repeated effort to derive the equations for three-dimensional wave-induced current. Via the vertical momentum equation and a proper coordinat...After the approach by Mellor （2003, 2008）, the present paper reports on a repeated effort to derive the equations for three-dimensional wave-induced current. Via the vertical momentum equation and a proper coordinate transformation, the phase-averaged wave dynamic pressure is well treated, and a continuous and depth-dependent radiation stress tensor, rather than the controversial delta Dirac function at the surface shown in Mellor （2008）, is provided. Besides, a phase-averaged vertical momentum flux over a sloping bottom is introduced. All the inconsistencies in Mellor （2003, 2008）, pointed out by Ardhuin et al. （2008） and Bennis and Ardhuin （2011）, are overcome in the presently revised equations. In a test case with a sloping sea bed, as shown in Ardhuin et al. （2008）, the wave-driving forces derived in the present equations are in good balance, and no spurious vertical circulation occurs outside the surf zone, indicating that Airy’s wave theory and the approach of Mellor （2003, 2008） are applicable for the derivation of the wave-induced current model.展开更多
基金supported by the National Natural Science Foundation of China(No.42176020)the National Key Research and Development Program(No.2022 YFC3105002).
文摘The effect of Stokes drift production(SDP),which includes Coriolis-Stokes forcing,Langmuir circulation,and Craik-Lei-bovich vortexes,on the upper ocean during typhoon passage in the Bohai Sea(BS),China,is investigated by using a coupled wave-current model.The role of SDP in turbulent mixing and the further dynamics during the entire typhoon period are comprehensively stud-ied.Experimental results show that SDP greatly increases turbulent mixing at all depths under typhoon conditions by up to seven times that under normal weather conditions.SDP generally strengthens sea surface cooling by more than 0.4℃,with the maximum reduction in sea surface temperature(SST)at the during-typhoon stage exceeding 2℃,which is approximately seven times larger than that under normal weather conditions.The SDP-induced decrease in current speed can exceed 0.2ms^(-1),and the change in current direction is generally opposite the wind direction.These results suggest that Stokes drift depresses the effect of strong winds on currents by intensifying turbulent mixing.Mixed layer depth(MLD)is distinctly increased by O(1)during typhoons due to SDP and can deepen by more than 5m.In addition,the continuous effects of SDP on SST,current,and MLD at the after-typhoon stage indi-cate a hysteretic response between SDP and typhoon actions.
基金The National Natural Science Foundation of China under contract No.41376183the High Resolution Images Services Special Projection for ocean applicationsthe Oceanography Public Welfare Scientific Research Project-Marine of China under contract No.201205012
文摘The SAR（Synthetic Aperture Radar） has the capabilities for all-weather day and night use. In the case of determining the effects of oil spill dumping, the oil spills areas are shown as dark spots in the SAR images.Therefore, using SAR data to detect oil spills is becoming progressively popular in operational monitoring, which is useful for oceanic environmental protection and hazard reduction. Research has been conducted on the polarization decomposition and scattering characteristics of oil spills from a scattering matrix using allpolarization of the SAR data, calculation of the polarization parameters, and utilization of the CPD（Co-polarized Phase Difference） of the oil and the sea, in order to extract the oil spill information. This method proves to be effective by combining polarization parameters with the characteristics of oil spill. The results show that when using Bragg, the oil spill backscattering machine with Enopy and a mean scatter α parameter. The oil spill can be successfully identified. However, the parameter mechanism of the oil spill remains unclear. The use of CPD can easily extract oil spill information from the ocean, and the polarization research provides a base for oil spill remote sensing detection.
基金supported by National Key Basic Research and Development Projects of China[grant number 2016YFA0600601]the National Natural Science Foundation of China[grant numbers 41530503,41405045,and 41605027]
文摘The northern edge of the East Asian summer monsoon （EASM） is identified using the pentad total column water vapor obtained from ERA-Interim reanalysis data during 1979-2015.Empirical orthogonal function analysis is applied to study the meridional displacement of the northern edge of the EASM during the study period,and the results show an interdecadal southward shift around 1993/1994 and an indistinct northward displacement after 2007/2008.To focus on the interdecadal change around 1993/1994,composite analysis using the difference between 1979-1993 and 1994-2007 is employed.Through examination of the differences between these two periods,a significant anticyclonic anomaly is found over Mongolia,suggesting a pronounced interdecadal weakening of the Mongolian low during 1994-2007.Thus,northward advancement of the EASM may have been prevented by the anomalous northerly flow to the east of the weakened Mongolian low after 1993.Further study shows that the interdecadal weakening of the Mongolian low might be attributable to the meridional inhomogeneity of surface warming over the northern part of East Asia.Previous studies suggest that such meridional inhomogeneity would lead to a reduction in local atmospheric baroclinicity,and thus the suppression of extratropical cyclone activity over Mongolia,resulting in a southward withdrawal of the northern edge of the EASM on the interdecadal timescale.
基金This work was supported by Natural Science Foundation of Guangdong Province(Grant Nos.04102749&04009790)President Foundation of 0ceanological Science and Technology,South China Sea Branch,State 0ceanic Administration of China(Grant Nos.0104&0311)+1 种基金Research Foundation of Tropical 0ceanological and Meteorological Science(Grant No.200414)the Air-Sea Interface Heat Exchange of the Typhoon Project of Shanghai Typhoon Institute Foundation.
文摘In order to explore the interaction be- tween the sea and monsoon in the South China Sea, the heat exchanges at air-sea interface during mon- soon periods in 1986 were calculated using observa- tional data. It shows that when the summer monsoon bursts and prevails over the South China Sea, the air-sea interface heat exchange is strong and the latent heat rises rapidly in the intertropical conver- gence zone and the tropic cyclone system near 20.49°N, 114.14°E. On May 24, 1986, the sensible heat became positive in the typhoon system. The heating exchange indicates that heat is transported from ocean to atmosphere, with major contribution of latent heat. When the summer monsoon prevails over the South China Sea and the weather is fine, even SST (sea surface temperature) is high, but sensible heat appears to be negative. The heat exchange indicates that heat is transported from atmosphere to ocean, with major contribution of short-wave radiation absorbed by sea surface and sensible heat. When summer monsoon is over and the northeast monsoon prevails over the South China Sea, the heat ex- change at air-sea interface is very strong. The heat- ing exchange shows that the ocean heats the at- mosphere, with major contribution of latent heat when cold air arrives at the sea surface and the sensible heat rises to positive rapidly. Therefore it can be concluded that the heat exchange at air-sea interface is different from the SST in South China Sea. Whenthe summer monsoon prevails over the South China Sea, the main trend is the ocean responding to the atmosphere.
文摘After the approach by Mellor （2003, 2008）, the present paper reports on a repeated effort to derive the equations for three-dimensional wave-induced current. Via the vertical momentum equation and a proper coordinate transformation, the phase-averaged wave dynamic pressure is well treated, and a continuous and depth-dependent radiation stress tensor, rather than the controversial delta Dirac function at the surface shown in Mellor （2008）, is provided. Besides, a phase-averaged vertical momentum flux over a sloping bottom is introduced. All the inconsistencies in Mellor （2003, 2008）, pointed out by Ardhuin et al. （2008） and Bennis and Ardhuin （2011）, are overcome in the presently revised equations. In a test case with a sloping sea bed, as shown in Ardhuin et al. （2008）, the wave-driving forces derived in the present equations are in good balance, and no spurious vertical circulation occurs outside the surf zone, indicating that Airy’s wave theory and the approach of Mellor （2003, 2008） are applicable for the derivation of the wave-induced current model.
