Using NCEP/NCAR reanalysis geopotential height （GHT） and wind at 850 hPa, GHT at 500 hPa, precipitation rate, sea level pressure （SLP） and precipitation observations from more than 600 stations nationwide in June-...Using NCEP/NCAR reanalysis geopotential height （GHT） and wind at 850 hPa, GHT at 500 hPa, precipitation rate, sea level pressure （SLP） and precipitation observations from more than 600 stations nationwide in June-August from 1951 to 2006, and focusing on the East Asia-West Pacific region （10°-80°N, 70°-180°E）, interannual variation of East Asian summer monsoon （EASM） and its correlations with general circulation and precipitation patterns are studied by using statistical diagnostic methods such as 9-point high pass filtering, empirical orthogonal function （EOF） analysis, composite analysis and other statistical diagnosis, etc. It is concluded as follows： （1） EOF analysis of SLP in the East Asia-West Pacific region shows the existence of the zonal dipole oscillation mode （APD） between the Mongolia depression and the West Pacific high, and APD index can be used as an intensity index of EASM. （2） EOF analysis of GHT anomalies at 500 hPa in the East Asia-West Pacific region shows that the first EOF mode is characterized with an obvious meridional East Asian pattern （EAP）, and EAP index can also be used as an EASM intensity index. （3） The composite analysis of high/low APD index years reveals the close correlation of APD index with EAP at 500 hPa （or 850 hPa）. The study shows an obvious opposite correlation exists between APD index and EAP index with a correlation coefficient of -0.23, which passes the confidence test at 0.10 level. （4） Both APD and EAP indexes are closely correlated with precipitation during flood-prone season in China and precipitation rate over the East Asia-West Pacific region. The significant correlation area at 5% confidence level is mainly located from the southern area of the Yangtze River valley to the ocean around southern Japan, and the former is a positive correlation and the latter is a negative one.展开更多
Surface-and subsurface-dwelling planktonic foraminifera from the upper 43 m of Hole A at the Ocean Drilling Program (ODP) Site 807,which was recovered from the western Pacific warm pool during ODP Leg 130,were analyze...Surface-and subsurface-dwelling planktonic foraminifera from the upper 43 m of Hole A at the Ocean Drilling Program (ODP) Site 807,which was recovered from the western Pacific warm pool during ODP Leg 130,were analyzed for stable oxygen and carbon isotopes.By comparing these results with data from ODP Site 851 in the eastern equatorial Pacific,this study has reconstructed the paleoceanographic changes in upper ocean waters in the equatorial Pacific since 2.5 Ma.During the period from 1.6-1.4 Ma,the oxygen isotopes of surface and subsurface waters were found to markedly change in the western and eastern equatorial Pacific,further confirming the final formation of the well-defined asymmetric east-west (E-W) pattern at that time.This feature was similar to the zonal temperature gradient (sea surface temperature is higher in the west and lower in the east) and the asymmetric upper water structure (thermocline depth is deeper in the west and shallower in the east) in the modern equatorial Pacific.The zonal gradient change of subsurface water δ18O was greater than that of surface water δ18O,indicating that the formation of the asymmetric E-W pattern in the equatorial Pacific should be much more related to the shoaled thermocline and markedly decreased subsurface water temperature in the eastern equatorial Pacific.Moreover,since ～1.6 Ma,the carbon isotopic differences between surface and subsurface waters clearly decreased in the equatorial Pacific,and their long-term eccentricity periods changed from 400 ka to ～500 ka,reflecting the reorganization of the ocean carbon reservoir.This probably resulted from the deep water reorganization in the Southern Ocean at that time and its enhanced influence on the tropical Pacific (especially subsurface water).Our study demonstrates that the tropical ocean plays an important role in global climate change.展开更多
基金funded by the Ministry of Science and Technology of the People’s Republic of China,No.2007DFB20210National Natural Science Foundation of China,No.90502003JICA China-Japan Technical Cooperative Project "China-Japanese Cooperative Research Center on Meteorological Disasters"
文摘Using NCEP/NCAR reanalysis geopotential height （GHT） and wind at 850 hPa, GHT at 500 hPa, precipitation rate, sea level pressure （SLP） and precipitation observations from more than 600 stations nationwide in June-August from 1951 to 2006, and focusing on the East Asia-West Pacific region （10°-80°N, 70°-180°E）, interannual variation of East Asian summer monsoon （EASM） and its correlations with general circulation and precipitation patterns are studied by using statistical diagnostic methods such as 9-point high pass filtering, empirical orthogonal function （EOF） analysis, composite analysis and other statistical diagnosis, etc. It is concluded as follows： （1） EOF analysis of SLP in the East Asia-West Pacific region shows the existence of the zonal dipole oscillation mode （APD） between the Mongolia depression and the West Pacific high, and APD index can be used as an intensity index of EASM. （2） EOF analysis of GHT anomalies at 500 hPa in the East Asia-West Pacific region shows that the first EOF mode is characterized with an obvious meridional East Asian pattern （EAP）, and EAP index can also be used as an EASM intensity index. （3） The composite analysis of high/low APD index years reveals the close correlation of APD index with EAP at 500 hPa （or 850 hPa）. The study shows an obvious opposite correlation exists between APD index and EAP index with a correlation coefficient of -0.23, which passes the confidence test at 0.10 level. （4） Both APD and EAP indexes are closely correlated with precipitation during flood-prone season in China and precipitation rate over the East Asia-West Pacific region. The significant correlation area at 5% confidence level is mainly located from the southern area of the Yangtze River valley to the ocean around southern Japan, and the former is a positive correlation and the latter is a negative one.
基金supported by the National Natural Science Foundation of China (40806020)the National Basic Research Program of China (2007CB815901)+1 种基金the Doctoral Program Foundation of Institutions of Higher Education of China (200802471034)the China Ocean Mineral Resources R&D Association (DY115-01-2-3)
文摘Surface-and subsurface-dwelling planktonic foraminifera from the upper 43 m of Hole A at the Ocean Drilling Program (ODP) Site 807,which was recovered from the western Pacific warm pool during ODP Leg 130,were analyzed for stable oxygen and carbon isotopes.By comparing these results with data from ODP Site 851 in the eastern equatorial Pacific,this study has reconstructed the paleoceanographic changes in upper ocean waters in the equatorial Pacific since 2.5 Ma.During the period from 1.6-1.4 Ma,the oxygen isotopes of surface and subsurface waters were found to markedly change in the western and eastern equatorial Pacific,further confirming the final formation of the well-defined asymmetric east-west (E-W) pattern at that time.This feature was similar to the zonal temperature gradient (sea surface temperature is higher in the west and lower in the east) and the asymmetric upper water structure (thermocline depth is deeper in the west and shallower in the east) in the modern equatorial Pacific.The zonal gradient change of subsurface water δ18O was greater than that of surface water δ18O,indicating that the formation of the asymmetric E-W pattern in the equatorial Pacific should be much more related to the shoaled thermocline and markedly decreased subsurface water temperature in the eastern equatorial Pacific.Moreover,since ～1.6 Ma,the carbon isotopic differences between surface and subsurface waters clearly decreased in the equatorial Pacific,and their long-term eccentricity periods changed from 400 ka to ～500 ka,reflecting the reorganization of the ocean carbon reservoir.This probably resulted from the deep water reorganization in the Southern Ocean at that time and its enhanced influence on the tropical Pacific (especially subsurface water).Our study demonstrates that the tropical ocean plays an important role in global climate change.
