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Search Results: 1 - 10 of 4251 matches for " interdecadal variation "
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The interdecadal variation of Indonesian Throughflow and its mechanism
Xiangfeng Meng,Dexing Wu,Ruijin Hu,Jian Lan
Chinese Science Bulletin , 2004, DOI: 10.1360/03wd0540
Abstract: The interdecadal variation of the volume and heat transport of Indonesian Throughflow (ITF) and its mechanism are preliminarily studied on the basis of the updated SODA data. It is found that the interdecadal variation of ITF’s volume transport is mainly concentrated in upper 714 m and that of ITF’s heat transport is mainly confined to upper 450 m. There is fairly consistent interdecadal variation in the depth-integrated seawater pressure above different depths in the region south of Davao, north of New Guinea and southwest of Australia. The depth-integrated pressure difference between northwest of Australia and south of Java has best correspondence with ITF’s volume transport on interdecadal time scales. The relation between the wind stress on the Pacific and ITF’s volume transport on interdecadal time scales is studied based on Island Rule. It is shown that both the wind stress along the zonal lines just south of Australia and the Equator act as the dominant contributors to ITF’s volume transport, with the latter dominating the phase of ITF’s interdecadal variation. These results indicate that the atmospheric forcing and oceanic adjustment in the tropical region both contribute significantly to the ITF’s interdecadal variation.
Interannual and interdecadal variabilities in SST anomaly over the eastern equatorial Pacific
Weihong Qian,Yafen Zhu,Qian Ye
Chinese Science Bulletin , 1999, DOI: 10.1007/BF02885550
Abstract: The global sea surface temperature (SST) anomaly data from 1950 to 1996 were used to analyze spatial characters of interdecadal SST variations. A wavelet transform was made for the equatorial eastern Pacific SST anomaly time series. Results show that there are three remarkable timescale SST variations: 130-month interdecadal variation, 57-month interannual variation and 28-month quasi2-a variation. Based on this result, an EI Ni o event was predicted in the early part of 1997.
Thunder Events in China: 1980-2008
ZHENG Lin-Lin,SUN Jian-Hua,WEI Jie,
ZHENG Lin-Lin
,SUN Jian-Hu,WEI Jie

大气和海洋科学快报 , 2010,
Abstract: Using data collected at 517 weather stations in contiguous China over the period 1980-2008, characteristics of thunder events have been investigated. These characteristics include geographical distribution, interdecadal variation, annual variation, and seasonal variation. The areas with the highest frequencies of thunder events are located in the central Tibetan Plateau, Yunnan, Guangxi, and Guangdong. The annual number of thunder days increases from northern to southern China. But the frequency of thunder events over mountains and plateaus is much higher than the frequency of events over plains in the same latitude. The interdecadal variation of events shows that the frequency of thunder occurrences was highest during the 1980s, decreased during the 1990s, and increased slightly afterwards. Thunder occurrences vary with the season, northward in May and retreating southward in September.
How Well do Existing Indices Measure the Strength of the East Asian Winter Monsoon?

WANG Lin,CHEN Wen,

大气科学进展 , 2010,
Abstract: Defining the intensity of the East Asian winter monsoon (EAWM) with a simple index has been a difficult task. This paper elaborates on the meanings of 18 existing EAWM strength indices and classifies them into four categories: low level wind indices, upper zonal wind shear indices, east-west pressure contrast indices, and East Asian trough indices. The temporal/spatial performance and prediction potential of these indices are then analyzed for the 1957--2001 period. It reveals that on the decadal timescale, most indices except the east--west pressure contrast indices can well capture the continuous weakening of the EAWM around 1986. On the interannual timescale, the low level wind indices and East Asian trough indices have the best predictability based on knowledge of the El Nino-Southern Oscillation and Arctic Oscillation, respectively. All the 18 existing indices can well describe the EAWM-related circulation, precipitation, and lower tropospheric air temperature anomalies. However, the variations of surface air temperature over large areas of central China cannot be well captured by most indices, which is possibly related to topographic effects. The results of this study may provide a possible reference for future studies of the EAWM.
Interannual and interdecadal variabilities in SST anomaly over the eastern equatorial Pacific

Weihong Qian,Yafen Zhu,Qian Ye,

科学通报(英文版) , 1999,
Abstract: The global sea surface temperature (SST) anomaly data from 1950 to 1996 were used to analyze spatial characters of interdecadal SST variations. A wavelet transform was made for the equatorial eastern Pacific SST anomaly time series. Results show that there are three remarkable timescale SST variations: 130-month interdecadal variation, 57-month interannual variation and 28-month quasi2-a variation. Based on this result, an EI Ni?o event was predicted in the early part of 1997.
Interdecadal variations in global climate and earth rotation rate
Qian Weihong
Chinese Science Bulletin , 1997, DOI: 10.1007/BF02882931
Abstract:
Interdecadal Variations of Phase Delays Between Two Ni(n)o Indices at Different Time Scales

BIAN Jianchun,YANG Peicai,

大气科学进展 , 2005,
Abstract: Phase delays between two Nino indices-sea surface temperatures in Nino regions 1+2 and 3.4(1950-2001)-at different time scales are detected by wavelet analysis. Analysis results show that thereare two types of period bifurcations in the Nino indices and that period bifurcation points exist only in the region where the wavelet power is small. Interdecadal variation features of phase delays between the two indices vary with different time scales. In the periods of 40-72 months, the phase delay changes its sign in 1977: Nino 1+2 indices are 2-4 months earlier than Nino 3.4 indices before 1977, but 3-6 months later afterwards. In the periods of 20-40 months, however, the phase delay changes its sign in another way:Nino 1+2 indices are 1-4 months earlier before 1980 and during 1986-90, but 1-4 months later during 1980-83 and 1993-2001.
Eurasian Snow Cover Variability and Its Association with Summer Rainfall in China

WU Bingyi,YANG Kun,ZHANG Renhe,

大气科学进展 , 2009,
Abstract: This study investigates the statistical linkage between summer rainfall in China and the preceding spring Eurasian snow water equivalent (SWE), using the datasets of summer rainfall observations from 513 stations, satellite-observed snow water equivalent, and atmospheric circulation variables in the NCEP/NCAR re-analysis during the period from 1979 to 2004. The first two coupled modes are identified by using the singular value decomposition (SVD) method. The leading SVD mode of the spring SWE variability shows a coherent negative anomaly in most of Eurasia with the opposite anomaly in some small areas of the Tibetan Plateau and East Asia. The mode displays strong interannual variability, superposed on an interdecadal variation that occurred in the late 1980s, with persistent negative phases in 1979--1987 and frequent positive phases afterwards. When the leading mode is in its positive phase, it corresponds to less SWE in spring throughout most of Eurasia. Meanwhile, excessive SWE in some small areas of the Tibetan Plateau and East Asia, summer rainfall in South and Southeast China tends to be increased, whereas it would be decreased in the up-reaches of the Yellow River. In recent two decades, the decreased spring SWE in Eurasia may be one of reasons for severe droughts in North and Northeast China and much more significant rainfall events in South and Southeast China. The second SVD mode of the spring SWE variability shows opposite spatial variations in western and eastern Eurasia, while most of the Tibetan Plateau and East Asia are in phase. This mode significantly correlates with the succeeding summer rainfall in North and Northeast China, that is, less spring SWE in western Eurasia and excessive SWE in eastern Eurasia and the Tibetan Plateau tend to be associated with decreased summer rainfall in North and Northeast China.
Flooding 1990s along the Yangtze River, has it concern of global warming?

GONG Dao-yi,ZHU Jin-hong,WANG Shao-wu,

地理学报 , 2001,
Abstract: There were a series of severe floods along the middle to lower reaches of the Yangtze River (Changjiang River) in China during the 1990s. The extensive summer (June, July and August) precipitation is mostly responsible for the flooding. The summer rainfall in the 1980s and the 1990s is much higher than that in the previous 3 decades. The means for 1990-1999 is +87.62 mm above normal, marked the 1990s the wettest decade since the 1950s. Six stations with a time span of 1880-1999 are selected to establish century -long rainfall series. This series also shows that the 1990s is the wettest decade during the last 120 years. In the wettest 12 years, four occurred in the 1990s (1991,1996,1998 and 1999). Both global and China’s temperature show there is a relative lower air temperature during the 1960-1970s, and a rapid warming in the 1980-1990s. Comparisons of rainfall between 1960-1979 and 1980-1999 show there are dramatic changes. In the cold period 1960-1979, the summer rainfall along the Yangtze River is 3.8 % to 4.7 % below the normal, during the warm period 1980-1999, over 8.4 % to 18.2 % of summer rainfall occurs. Over the whole eastern China, the summer rainfall shows opposite spatial patterns from the 1960-1970s to 1980-1990s. The consistent trend toward more rainfall with global warming is also presented by the greenhouse scenario modeling. A millennial Drought/flood Index for the middle to lower reaches of the Yangtze River showed that although the surplus summer rainfall in the 1990s is the severest during the past 150 years, it is not outstanding in the context of past millennium. Power spectra of the Drought/flood Index show significant interdecadal periods at 33.3 and 11.8 years. Thus, both the natural inter-decadal variations and the global warming may play important roles in the frequent floods witnessed during the last two decades.
Interannual and interdecadal variations in the North Atlantic Oscillation spatial shift
XiaoJian Zhang,LiYa Jin,ChunZhu Chen,DongSheng Guan,MingZhi Li
Chinese Science Bulletin , 2011, DOI: 10.1007/s11434-011-4607-8
Abstract: The spatial shift of the North Atlantic Oscillation (NAO) is analyzed by using the Twentieth Century Reanalysis version 2 dataset and identifying NAO action centers directly on winter mean sea-level pressure (SLP) anomaly maps. The spatial shift of the NAO is characterized by four NAO spatial shift indices: the zonal and meridional shifts of the NAO southern and northern action centers. It is found that the zonal and meridional shift trends of the NAO action centers move along a path of southwest-northwest direction. Spectral analysis shows that the four NAO spatial shift indices have periodicity of 2–6 years and the NAO index has periodicity of 2–3 years in terms of high-frequency variations. On a decadal time scale, the NAO spatial shift indices are closely (positively) related to the NAO index, which is in agreement with previous studies of the relationship between the NAO index and the spatial shift of the NAO pattern. However, there is no relationship between the NAO index and the meridional shift of the northern action center on an interannual time scale. The significant relationship between the NAO index and the interannual variability of NAO spatial shift indices is very likely to be associated with synoptic-scale Rossby wave breaking, which generates surface pressure anomalies and thus affects the phase and pattern of the NAO. The correlations of winter westerly winds over 90°W-0° and the NAO index and the NAO spatial shift indices have a ‘+ + ’ structure from the Equator to the North Pole. Although there is close correlation between the NAO spatial shift indices and the strength of the zonal winds in the North Atlantic region, the effect of the zonal winds on the NAO spatial shift differs at different latitudes. Hence, the role of the zonal winds is probably a result of the NAO spatial shifts.
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