The North American Dipole(NAD)is a north-south seesaw pattern of sea level pressure anomalies over the western tropical North Atlantic and northeastern North America.Previous observational studies have demonstrated th...The North American Dipole(NAD)is a north-south seesaw pattern of sea level pressure anomalies over the western tropical North Atlantic and northeastern North America.Previous observational studies have demonstrated that the NAD can affect the outbreak of El Niño-Southern Oscillation(ENSO)events.The present study analyzed the NAD-ENSO relationship as simulated by a coupled ocean-atmosphere model-namely,the Flexible Global Ocean-Atmosphere-Land System model,gridpoint version 2(FGOALS-g2).Results indicated that the model can replicate a distinct dipole comprised of a low over northeastern North America and a high over the western tropical North Atlantic,which is the signature feature of the NAD.Further analysis verified that the winter NAD can initiate the central equatorial Pacific warming in the subsequent winter by effectively forcing an anticyclonic flow and sea surface temperature(SST)warming over the northeastern subtropical Pacific(NESP)during late winter or early spring.In addition,the probability of an El Niño event was increased by a factor of 1.8 in the assimilation experiment with the NAD.By comparison,the winter Northern Atlantic Oscillation had no significant impact on the occurrence of ENSO a year later owing to its failure to induce the SST and surface wind anomalies over the NESP.展开更多
Gaseous dibenzo-7-phosphanorbornadiene P-sulfide anions APS （A C14H10 or anthracene） were generated via electrospray ionization, and characterized by magnetic-bottle photoelec- tron spectroscopy, velocity-map imagi...Gaseous dibenzo-7-phosphanorbornadiene P-sulfide anions APS （A C14H10 or anthracene） were generated via electrospray ionization, and characterized by magnetic-bottle photoelec- tron spectroscopy, velocity-map imaging （VMI） photoelectron spectroscopy, and quantum chemical calculations. The electron affinity （EA） and spin-orbit （SO） splitting of the APS＂ radical are determined from the photoelectron spectra and Franck-Condon factor simulations to be EA （2.62-4-0.05） eV and SO splitting （43-4-7） meV. VMI photoelectron images show strong and sharp peaks near the detachment threshold with an identical electron kinetic energy （eKE） of 17.9 meV at three different detachment wavelengths, which are therefore assigned to autodetachment from dipole-bound anion states. The B3LYP/6-31＋＋G（d,p） calculations indicate APS has a dipole moment of 3.31 Debye, large enough to support a dipole-bound electron.展开更多
Based on a coupled ocean-atmosphere model, the response of the Indian Ocean Dipole (IOD) mode to global warming is investigated with a six member ensemble of simulations for the period 1850-2100. The model can simulat...Based on a coupled ocean-atmosphere model, the response of the Indian Ocean Dipole (IOD) mode to global warming is investigated with a six member ensemble of simulations for the period 1850-2100. The model can simulate the IOD features rea-listically, including the east-west dipole pattern and the phase locking in boreal autumn. The ensemble analysis suppresses internal variability and isolates the radiative forced response. In response to increasing greenhouse gases, a weakening of the Walker circula-tion leads to the easterly wind anomalies in the equatorial Indian Ocean and the shoaling thermocline in the eastern equatorial Indian Ocean (EEIO), and sea surface temperature and precipitation changes show an IOD-like pattern in the equatorial Indian Ocean. Al-though the thermocline feedback intensifies with shoaling, the interannual variability of the IOD mode surprisingly weakens under global warming. The zonal wind feedback of IOD is found to weaken as well, due to decreased precipitation in the EEIO. Therefore, the atmospheric feedback decreases much more than the oceanic feedback increases, causing the decreased IOD variance in this model.展开更多
A single cesium atom is trapped in a far-off-resonance optical dipole trap （FORT） from the magneto-optical trap （MOT） and directly imaged by using a charge-coupled device （CCD） camera. The binary single-atom ste...A single cesium atom is trapped in a far-off-resonance optical dipole trap （FORT） from the magneto-optical trap （MOT） and directly imaged by using a charge-coupled device （CCD） camera. The binary single-atom steps and photon anti-bunching are observed by a photon-counting-based HBT system using fluorescence light. The average atom dwelling time in the FORT is about 9 s. To reduce the background noise in the detection procedure we employ a weak probe laser tuned to the D1 line to il- lurninate the single atom from the direction perpendicular to the large-numerical-aperture collimation system. The second or- der degree of coherence g（2）（r）=0.12_＋0.02 is obtained directly from the fluorescence light of the single atom without deducting the background. The background light has been suppressed to 10 counts per 50 ms, which is much lower compared with the reported results. The measured g（2）（r） is in good agreement with theoretical analysis. The system provides a simple and effi- cient method to manipulate and measure single neutral atoms, and opens a way to create an efficient controlled single-photon source.展开更多
The E1 Nifio-Southern Oscillation （ENSO） phenomenon in the tropical Pacific has been a focus of ocean and climate studies in the last few decades. Recently, the short-term climate variability in the tropical Indian ...The E1 Nifio-Southern Oscillation （ENSO） phenomenon in the tropical Pacific has been a focus of ocean and climate studies in the last few decades. Recently, the short-term climate variability in the tropical Indian Ocean has attracted increasingly more attention, especially with the proposition of the Indian Ocean Dipole （IOD） mode. However, these phenomena are often stud- ied separately without much consideration of their interaction. Observations reveal a striking out-of-phase relationship between zonal gradients of sea surface height anomaly （SSHA） and sea surface temperature anomaly （SSTA） in the tropical Indian and Pacific Oceans. Since the two oceans share the ascending branch of the Walker cells over the warm pool, the variation within one of them will affect the other. The accompanied zonal surface wind anomalies are always opposite over the two basins, thus producing a tripole structure with opposite zonal gradients of SSHA/SSTA in the two oceans. This mode of variability has been referred to as Indo-Pacific Tripole （IPT）. Based on observational data analyses and a simple ocean-atmosphere coupled model, this study tries to identify the characteristics and physical mechanism of IPT with a particular emphasis on the rela- tionships among ENSO, IOD, and IPT. The model includes the basic oceanic and atmospheric variables and the feedbacks between them, and takes into account the inter-basin connection through an atmospheric bridge, thus providing a valuable framework for further research on the short-term tropical climate variability.展开更多
基金jointly supported by the National Natural Science Foundation of China[grant number 41975070]the State Key Labo-ratory of Tropical Oceanography,South China Sea Institute of Oceanol-ogy,Chinese Academy of Sciences[project number LTO1901].
文摘The North American Dipole(NAD)is a north-south seesaw pattern of sea level pressure anomalies over the western tropical North Atlantic and northeastern North America.Previous observational studies have demonstrated that the NAD can affect the outbreak of El Niño-Southern Oscillation(ENSO)events.The present study analyzed the NAD-ENSO relationship as simulated by a coupled ocean-atmosphere model-namely,the Flexible Global Ocean-Atmosphere-Land System model,gridpoint version 2(FGOALS-g2).Results indicated that the model can replicate a distinct dipole comprised of a low over northeastern North America and a high over the western tropical North Atlantic,which is the signature feature of the NAD.Further analysis verified that the winter NAD can initiate the central equatorial Pacific warming in the subsequent winter by effectively forcing an anticyclonic flow and sea surface temperature(SST)warming over the northeastern subtropical Pacific(NESP)during late winter or early spring.In addition,the probability of an El Niño event was increased by a factor of 1.8 in the assimilation experiment with the NAD.By comparison,the winter Northern Atlantic Oscillation had no significant impact on the occurrence of ENSO a year later owing to its failure to induce the SST and surface wind anomalies over the NESP.
基金supported by the U.S.Department of Energy(DOE),Office of Science,Office of Basic EnergySciences,Division of Chemical Sciences,Geosciences and Biosciences,and was performed using EMSLa national scientific user facility sponsored by DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory,which is operated by Battelle Memorial Institute for the DOEsupported by the National Science Foundation under Grant(No.CHE-1664799)
文摘Gaseous dibenzo-7-phosphanorbornadiene P-sulfide anions APS （A C14H10 or anthracene） were generated via electrospray ionization, and characterized by magnetic-bottle photoelec- tron spectroscopy, velocity-map imaging （VMI） photoelectron spectroscopy, and quantum chemical calculations. The electron affinity （EA） and spin-orbit （SO） splitting of the APS＂ radical are determined from the photoelectron spectra and Franck-Condon factor simulations to be EA （2.62-4-0.05） eV and SO splitting （43-4-7） meV. VMI photoelectron images show strong and sharp peaks near the detachment threshold with an identical electron kinetic energy （eKE） of 17.9 meV at three different detachment wavelengths, which are therefore assigned to autodetachment from dipole-bound anion states. The B3LYP/6-31＋＋G（d,p） calculations indicate APS has a dipole moment of 3.31 Debye, large enough to support a dipole-bound electron.
基金supported by the National Basic Research Program of China(2012CB955603)the Natural Science Foundation of China(41106010,41176006)+1 种基金the 111 Project(B07036)the Qianren Program
文摘Based on a coupled ocean-atmosphere model, the response of the Indian Ocean Dipole (IOD) mode to global warming is investigated with a six member ensemble of simulations for the period 1850-2100. The model can simulate the IOD features rea-listically, including the east-west dipole pattern and the phase locking in boreal autumn. The ensemble analysis suppresses internal variability and isolates the radiative forced response. In response to increasing greenhouse gases, a weakening of the Walker circula-tion leads to the easterly wind anomalies in the equatorial Indian Ocean and the shoaling thermocline in the eastern equatorial Indian Ocean (EEIO), and sea surface temperature and precipitation changes show an IOD-like pattern in the equatorial Indian Ocean. Al-though the thermocline feedback intensifies with shoaling, the interannual variability of the IOD mode surprisingly weakens under global warming. The zonal wind feedback of IOD is found to weaken as well, due to decreased precipitation in the EEIO. Therefore, the atmospheric feedback decreases much more than the oceanic feedback increases, causing the decreased IOD variance in this model.
基金supported by the State Basic Key Research Program of China (Grant No. 2012CB921601)China National Funds for Distinguished Young Scientists (Grant No. 11125418)the National Natural Science Foundation of China (Grant Nos. 10974125,61121064 and60978017)
文摘A single cesium atom is trapped in a far-off-resonance optical dipole trap （FORT） from the magneto-optical trap （MOT） and directly imaged by using a charge-coupled device （CCD） camera. The binary single-atom steps and photon anti-bunching are observed by a photon-counting-based HBT system using fluorescence light. The average atom dwelling time in the FORT is about 9 s. To reduce the background noise in the detection procedure we employ a weak probe laser tuned to the D1 line to il- lurninate the single atom from the direction perpendicular to the large-numerical-aperture collimation system. The second or- der degree of coherence g（2）（r）=0.12_＋0.02 is obtained directly from the fluorescence light of the single atom without deducting the background. The background light has been suppressed to 10 counts per 50 ms, which is much lower compared with the reported results. The measured g（2）（r） is in good agreement with theoretical analysis. The system provides a simple and effi- cient method to manipulate and measure single neutral atoms, and opens a way to create an efficient controlled single-photon source.
文摘The E1 Nifio-Southern Oscillation （ENSO） phenomenon in the tropical Pacific has been a focus of ocean and climate studies in the last few decades. Recently, the short-term climate variability in the tropical Indian Ocean has attracted increasingly more attention, especially with the proposition of the Indian Ocean Dipole （IOD） mode. However, these phenomena are often stud- ied separately without much consideration of their interaction. Observations reveal a striking out-of-phase relationship between zonal gradients of sea surface height anomaly （SSHA） and sea surface temperature anomaly （SSTA） in the tropical Indian and Pacific Oceans. Since the two oceans share the ascending branch of the Walker cells over the warm pool, the variation within one of them will affect the other. The accompanied zonal surface wind anomalies are always opposite over the two basins, thus producing a tripole structure with opposite zonal gradients of SSHA/SSTA in the two oceans. This mode of variability has been referred to as Indo-Pacific Tripole （IPT）. Based on observational data analyses and a simple ocean-atmosphere coupled model, this study tries to identify the characteristics and physical mechanism of IPT with a particular emphasis on the rela- tionships among ENSO, IOD, and IPT. The model includes the basic oceanic and atmospheric variables and the feedbacks between them, and takes into account the inter-basin connection through an atmospheric bridge, thus providing a valuable framework for further research on the short-term tropical climate variability.
