Based on the 6-hour-interval reanalysis data with 1°× 1°resolution from the National Center for Environmental Prediction/the National Center for Atmospheric Research （NCEP/NCAR）, the eddy kinetic ener...Based on the 6-hour-interval reanalysis data with 1°× 1°resolution from the National Center for Environmental Prediction/the National Center for Atmospheric Research （NCEP/NCAR）, the eddy kinetic energy （EKE） budget of a southwest vortex （SWV） that caused heavy rainfall in Guangxi over South China （from 1200 UTC 11 to 0000 UTC 13 June） is calculated. The results are as follows： （a） The SWV is a kind of subtropical vortex, with characteristics of both an extratropical vortex and a tropical vortex. （b） In the case examined, large-scale circulation and other perturbation fields contributed to the formation and development of the SWV. （c） When the SWV moved from weak large-scale circulation EKE areas to strong ones, the EKE of the SWV increased, and vice versa. （d） Sub-grid processes and frictional dissipation were the main sinks of the SWV EKE, which contributed to the decay of the SWV. （e） The residual term （RES） and the Total （composite effect of all right hand side （rhs） terms except the RES in the EKE equation） varied almost in the same tendency, which kept the EKE varying in a moderate way. （f） The EKE between 550 hPa and 850 hPa increased most intensively, corresponding to the vertical stretching of the SWV.展开更多
Drought often lasts long and is thus closely related to slowly varying external forcing such as sea surface temperature(SST).Here,based on observed precipitation and SST data along with NCEP-DOE reanalysis data,the po...Drought often lasts long and is thus closely related to slowly varying external forcing such as sea surface temperature(SST).Here,based on observed precipitation and SST data along with NCEP-DOE reanalysis data,the possible impacts of North Atlantic SST on drought formation in Southwest China are investigated.Results show that northeast-southwest-orientated dipole SST anomalies in the mid-high latitudes of the North Atlantic are closely related to autumn drought in Southwest China;the linear correlation coefficient between them reaches 0.48 during 1979-2020,significant at the 0.001 level.The dipole SST anomalies trigger southeastward-propagating Rossby waves and induce barotropic cyclonic circulation anomalies over India and the western Tibetan Plateau.This enhances the upward motion in northern India and the western Tibetan Plateau and causes a compensating downdraft,reduced precipitation,and consequent drought formation in Southwest China.展开更多
The mixed layer depth （MLD） in the upper ocean is an important physical parameter for describing the upper ocean mixed layer. We analyzed several major factors influencing the climatological mixed layer depth （CMLD...The mixed layer depth （MLD） in the upper ocean is an important physical parameter for describing the upper ocean mixed layer. We analyzed several major factors influencing the climatological mixed layer depth （CMLD）, and established a numerical simulation in the South China Sea （SCS） using the Regional Ocean Model System （ROMS） with a high-resolution （1/12~x 1/12~） grid nesting method and 50 vertical layers. Several ideal numerical experiments were tested by modifying the existing sea surface boundary conditions. Especially, we analyzed the sensitivity of the results simulated for the CMLD with factors of sea surface wind stress （SSWS）, sea surface net heat flux （SSNHF）, and the difference between evaporation and precipitation （DEP）. The result shows that of the three factors that change the depth of the CMLD, SSWS is in the first place, when ignoring the impact of SSWS, CMLD will change by 26% on average, and its effect is always to deepen the CMLD; the next comes SSNHF （13%） for deepening the CMLD in October to January and shallowing the CMLD in February to September; and the DEP comes in the third （only 2%）. Moreover, we analyzed the temporal and spatial characteristics of CMLD and compared the simulation result with the ARGO observational data. The results indicate that ROMS is applicable for studying CMLD in the SCS area.展开更多
With NCEP/NCAR reanalysis daily data and SST for 1998, the paper investigates the features of summer monsoon low-frequency oscillation (LFO) over the South China Sea (SCS). Results show that SCS summer monsoon onset i...With NCEP/NCAR reanalysis daily data and SST for 1998, the paper investigates the features of summer monsoon low-frequency oscillation (LFO) over the South China Sea (SCS). Results show that SCS summer monsoon onset is enhanced because of its LFO. Low-frequency (LF) low-level convergence (divergence) region of SCS is in the LF positive (negative) rainfall area. LFO of the SCS region migrates from south to north in the meridian and from west to east in zonal direction. LF divergence of SCS is vertically compensating to each other between high and low level.展开更多
Concentrations of organic matter, iron and manganese in the deep sea surface sediments in the Nansha Islands sea area, South China Sea are measured. Horizontal and vertical distributions of iron and manganese are disc...Concentrations of organic matter, iron and manganese in the deep sea surface sediments in the Nansha Islands sea area, South China Sea are measured. Horizontal and vertical distributions of iron and manganese are discussed. The vertical distribution of iron and manganese in the sediments results from reduction, diffusion, and redeposition of manganese (or iron) oxide and hydroxide in the sediment. There are the maxima of iron and manganese in solid phase in the top of the sediment, which is caused by the penetration of O2 and the upward flux of Mn2+ ( or Fe2+ ). Manganese bacteria play a very important role in the cycle of solid-phase iron and manganese in the ocean environment. Manganese bacteria oxidize Mn2+ ( or Fe2+ ) in dissolved state to Mn4+ ( or Fe3+ ) in oxidized state under the aerobic condition, whereas they reduce iron and manganese in anaerobic conditions.展开更多
In this paper, we discussed the features of atmospheric circulations over Eurasia as a response to sea surface temperature anomalies （SSTAs） over the tropical Indian Ocean, the equatorial Pacific, Kuroshio and the N...In this paper, we discussed the features of atmospheric circulations over Eurasia as a response to sea surface temperature anomalies （SSTAs） over the tropical Indian Ocean, the equatorial Pacific, Kuroshio and the North Atlantic. Our results are shown as follows： （1） CAM3.0, driven by the combined SSTAs over the four oceanic regions, can simulate well the features of anomalous atmospheric circulations over Eurasia in January 2008, indicating that the effects of the SSTAs over these four regions were one of the key causes of the anomalous systems over Eurasia. （2） The SSTAs over each key region contributed to the intensification of blocking over the Urals Mountains and a main East Asian trough. However, the influence of the SSTAs over individual oceanic regions differed from one another in other aspects. The SSTAs over the North Atlantic had an impact on the 500-hPa anomalous height （Z500A） over the middle-high latitudes and had a somewhat smaller effect over the low latitudes. For the warm SSTAs over Kuroshio, the subtropical high was much stronger, spread farther north than usual, and had an anomalous easterly that dominated the northwest Pacific Ocean. The warm SSTAs over the tropical Indian Ocean could have caused a negative Z500A from West Asia to Middle Asia, a remarkably anomalous southwesterly from the Indian Ocean to the south of China and an anomalous anticyclone circulation over the South China Sea-Philippine Sea region. Because of the La Nifia event, the winter monsoon was stronger than normal, with an anomalously cooler northerly over the southeastern coastal areas of China. （3） The combined effects of the SSTAs over the four key regions were likely more important to the atmospheric circulation anomalies of January 2008 over Eurasia than the effects of individual or partly combined SSTAS. This unique SSTA distribution possibly led to the circulation anomalies over Eurasia in January 2008, especially the atmospheric circulation anomalies over the subtropics, which were more similar to those of the winter E1 Nifio events than to the circulation anomalies following La Nifia.展开更多
基金supported by the National Natural Science Foundation of China under Grant Nos. 40875021 and 40605016the foundation of the Institute of Heavy Rain, Wuhan under Grant No. IHR2007K05
文摘Based on the 6-hour-interval reanalysis data with 1°× 1°resolution from the National Center for Environmental Prediction/the National Center for Atmospheric Research （NCEP/NCAR）, the eddy kinetic energy （EKE） budget of a southwest vortex （SWV） that caused heavy rainfall in Guangxi over South China （from 1200 UTC 11 to 0000 UTC 13 June） is calculated. The results are as follows： （a） The SWV is a kind of subtropical vortex, with characteristics of both an extratropical vortex and a tropical vortex. （b） In the case examined, large-scale circulation and other perturbation fields contributed to the formation and development of the SWV. （c） When the SWV moved from weak large-scale circulation EKE areas to strong ones, the EKE of the SWV increased, and vice versa. （d） Sub-grid processes and frictional dissipation were the main sinks of the SWV EKE, which contributed to the decay of the SWV. （e） The residual term （RES） and the Total （composite effect of all right hand side （rhs） terms except the RES in the EKE equation） varied almost in the same tendency, which kept the EKE varying in a moderate way. （f） The EKE between 550 hPa and 850 hPa increased most intensively, corresponding to the vertical stretching of the SWV.
基金financially supported by the National Natural Science Foundation of China (NSFC) [grant numbers 42088101 and 41875099]。
文摘Drought often lasts long and is thus closely related to slowly varying external forcing such as sea surface temperature(SST).Here,based on observed precipitation and SST data along with NCEP-DOE reanalysis data,the possible impacts of North Atlantic SST on drought formation in Southwest China are investigated.Results show that northeast-southwest-orientated dipole SST anomalies in the mid-high latitudes of the North Atlantic are closely related to autumn drought in Southwest China;the linear correlation coefficient between them reaches 0.48 during 1979-2020,significant at the 0.001 level.The dipole SST anomalies trigger southeastward-propagating Rossby waves and induce barotropic cyclonic circulation anomalies over India and the western Tibetan Plateau.This enhances the upward motion in northern India and the western Tibetan Plateau and causes a compensating downdraft,reduced precipitation,and consequent drought formation in Southwest China.
基金Supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (No.KZCX1-YW-12-01)the National Natural Science Foundation of China (No.40821004),the National Natural Science Foundation of China (No.40806008)and the High Performance Computing Center,IOCAS
文摘The mixed layer depth （MLD） in the upper ocean is an important physical parameter for describing the upper ocean mixed layer. We analyzed several major factors influencing the climatological mixed layer depth （CMLD）, and established a numerical simulation in the South China Sea （SCS） using the Regional Ocean Model System （ROMS） with a high-resolution （1/12~x 1/12~） grid nesting method and 50 vertical layers. Several ideal numerical experiments were tested by modifying the existing sea surface boundary conditions. Especially, we analyzed the sensitivity of the results simulated for the CMLD with factors of sea surface wind stress （SSWS）, sea surface net heat flux （SSNHF）, and the difference between evaporation and precipitation （DEP）. The result shows that of the three factors that change the depth of the CMLD, SSWS is in the first place, when ignoring the impact of SSWS, CMLD will change by 26% on average, and its effect is always to deepen the CMLD; the next comes SSNHF （13%） for deepening the CMLD in October to January and shallowing the CMLD in February to September; and the DEP comes in the third （only 2%）. Moreover, we analyzed the temporal and spatial characteristics of CMLD and compared the simulation result with the ARGO observational data. The results indicate that ROMS is applicable for studying CMLD in the SCS area.
基金National Project of Technology (2001BA607B) Start-up Foundation of Ph.D. of the Chinese Academy of Meteorological Sciences
文摘With NCEP/NCAR reanalysis daily data and SST for 1998, the paper investigates the features of summer monsoon low-frequency oscillation (LFO) over the South China Sea (SCS). Results show that SCS summer monsoon onset is enhanced because of its LFO. Low-frequency (LF) low-level convergence (divergence) region of SCS is in the LF positive (negative) rainfall area. LFO of the SCS region migrates from south to north in the meridian and from west to east in zonal direction. LF divergence of SCS is vertically compensating to each other between high and low level.
基金supported by the National Natural Science Foundation of China(contract No.49706065)the Special Foundation of National Social Common Wealth Research(contract No.2001DIA50041)ZKCX2-SW-212 by Chinese Academy of Science
文摘Concentrations of organic matter, iron and manganese in the deep sea surface sediments in the Nansha Islands sea area, South China Sea are measured. Horizontal and vertical distributions of iron and manganese are discussed. The vertical distribution of iron and manganese in the sediments results from reduction, diffusion, and redeposition of manganese (or iron) oxide and hydroxide in the sediment. There are the maxima of iron and manganese in solid phase in the top of the sediment, which is caused by the penetration of O2 and the upward flux of Mn2+ ( or Fe2+ ). Manganese bacteria play a very important role in the cycle of solid-phase iron and manganese in the ocean environment. Manganese bacteria oxidize Mn2+ ( or Fe2+ ) in dissolved state to Mn4+ ( or Fe3+ ) in oxidized state under the aerobic condition, whereas they reduce iron and manganese in anaerobic conditions.
基金Special Funds for Public Welfare of China (GYHY(QX) 2008-06-005)Science and Technology Innovation Program of Jiangsu Province (CX09B_221Z)
文摘In this paper, we discussed the features of atmospheric circulations over Eurasia as a response to sea surface temperature anomalies （SSTAs） over the tropical Indian Ocean, the equatorial Pacific, Kuroshio and the North Atlantic. Our results are shown as follows： （1） CAM3.0, driven by the combined SSTAs over the four oceanic regions, can simulate well the features of anomalous atmospheric circulations over Eurasia in January 2008, indicating that the effects of the SSTAs over these four regions were one of the key causes of the anomalous systems over Eurasia. （2） The SSTAs over each key region contributed to the intensification of blocking over the Urals Mountains and a main East Asian trough. However, the influence of the SSTAs over individual oceanic regions differed from one another in other aspects. The SSTAs over the North Atlantic had an impact on the 500-hPa anomalous height （Z500A） over the middle-high latitudes and had a somewhat smaller effect over the low latitudes. For the warm SSTAs over Kuroshio, the subtropical high was much stronger, spread farther north than usual, and had an anomalous easterly that dominated the northwest Pacific Ocean. The warm SSTAs over the tropical Indian Ocean could have caused a negative Z500A from West Asia to Middle Asia, a remarkably anomalous southwesterly from the Indian Ocean to the south of China and an anomalous anticyclone circulation over the South China Sea-Philippine Sea region. Because of the La Nifia event, the winter monsoon was stronger than normal, with an anomalously cooler northerly over the southeastern coastal areas of China. （3） The combined effects of the SSTAs over the four key regions were likely more important to the atmospheric circulation anomalies of January 2008 over Eurasia than the effects of individual or partly combined SSTAS. This unique SSTA distribution possibly led to the circulation anomalies over Eurasia in January 2008, especially the atmospheric circulation anomalies over the subtropics, which were more similar to those of the winter E1 Nifio events than to the circulation anomalies following La Nifia.
