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1.
有关南半球大气环流与东亚气候的关系研究的若干新进展 总被引：14，自引：15，他引：14
南半球大气环流是全球大气环流的重要组成部分,也是影响气候变化和亚洲季风系统的一个重要因素.中国气象学家很早就注意到南半球大气环流对东亚夏季风降水的影响.近年来,有关南半球气候变率的研究目前正受到世界气象学家越来越多的关注.南半球中高纬大气资料的丰富及南极涛动的确定,使得认识南半球高中纬环流的年际变动规律及其与东亚气候关系成为可能.本文主要介绍近年来有关南极涛动的年际变化与沙尘天气发生频次及东亚冬春季气候的关系,古气候资料揭示的南极涛动与华北降水的关系,以及南半球大气环流与长江中下游夏季降水的关系和南极涛动变率的可预测性等方面的研究进展.并对未来研究方向作了初步的展望. 相似文献
2.
南极海冰首要模态呈现偶极子型异常,正负异常中心分别位于别林斯高晋海/阿蒙森海和威德尔海。过去研究表明冬春季节南极海冰涛动异常对后期南极涛动（Antarctic Oscillation,AAO）型大气环流有显著影响,而AAO可以通过经向遥相关等机制影响北半球大气环流和东亚气候。本文中我们利用观测分析发现南极海冰涛动从5～7月（May–July,MJJ）到8～10月（August–October, ASO）有很好的持续性,并进一步分析其对北半球夏季大气环流的可能影响及其物理过程。结果表明,MJJ南极海冰涛动首先通过冰气相互作用在南半球激发持续性的AAO型大气环流异常,使得南半球中纬度和极地及热带之间的气压梯度加大,在MJJ至JAS,纬向平均纬向风呈现显著的正负相间的从南极到北极的经向遥相关型分布。对流层中层位势高度场上,在澳大利亚北部到海洋性大陆区域,出现显著的负异常,在东亚沿岸从低纬到高纬呈现南北走向的“? + ?”太平洋—日本（Pacific–Japan,PJ）遥相关波列,其对应赤道中部太平洋及赤道印度洋存在显著的降水和海温负异常,西北太平洋至我国东部沿海地区存在显著降水正异常和温度负异常;低纬度北美洲到大西洋一带存在的负位势高度异常和北大西洋附近存在的正位势高度异常中心,构成一个类似于西大西洋型遥相关（Western Atlantic,WA）的结构,对应赤道南大西洋降水增加和南撒哈拉地区降水减少。从物理过程来看,南极海冰涛动首先通过局地效应影响Ferrel环流,进而通过经圈环流调整使得海洋性大陆区域和热带大西洋上方的Hadley环流上升支得到增强,海洋性大陆区域特别是菲律宾附近的热带对流活动偏强,激发类似于负位相的PJ波列,影响东亚北太平洋地区的大气环流,而热带大西洋对流增强和北传特征,则通过激发WA遥相关影响大西洋和欧洲地区的大气环流。以上两种通道将持续性MJJ至ASO南极海冰涛动强迫的大气环流信号从南半球中高纬度经热带地区传递到北半球中高纬地区,从而对热带和北半球夏季大气环流产生显著影响。 相似文献
3.
In this study, the anomalous characteristics of observed large-scale synoptic fields in the extreme East Asian summer monsoon (EASM) years are analyzed, and the impact of the local sea surface temperature (SST) anomaly over the western North Pacific (WNP) on the extreme EASM is investigated through sensitivity experiments of 28?years EASM simulations to the local SST over the WNP. The observation analysis reveals that the extreme EASM is influenced more by anomalous large-scale atmospheric features such as monsoon circulations and the western North Pacific subtropical high than the local SST anomaly over the WNP. However, the results of the sensitivity experiments show that the local SST anomaly has an implicit impact on the extreme EASM. The patterns of differences in precipitation between the experiment forced by observed SST in each year and the experiment forced by climatological SST over the WNP are opposite to anomaly patterns of observed precipitation in the extreme EASM years. This is because the SST anomaly over the WNP plays a role in reducing precipitation anomaly by changing surface latent heat flux and monsoon circulations. In particular, the local SST anomaly over the WNP decreases anomalies of large-scale circulations, i.e., the local Hadley and the Walker circulations. Thus, the local SST anomaly over the WNP plays a role in decreasing the interannual variability of the EASM. 相似文献
4.
Over the mid-latitude North Pacific, there is a close relationship between interannual variations of the sea surface temperature (SST) and surface shortwave radiation during boreal summer. The present study evaluates this relationship in coupled model simulations, forced model simulations, and retrospective forecasts. It is found that the simulation of this relationship in climate models is closely related to the model biases in the meridional gradients of mean SST and surface shortwave radiation. A southward shift in the region of large mean meridional gradients leads to a similar southward shift in the region of large correlation between the SST and shortwave radiation variations. The relationship is enhanced (weakened) when the mean meridional gradients are stronger (weaker) compared to observations. The shortwave radiation?CSST correlation is weak in individual forced simulations because of the interference of internally generated shortwave radiation variations. The shortwave radiation?CSST correlation increases significantly in the ensemble mean due to reduction of internally generated variability. The long-lead Climate Forecast System (CFS) forecasts have a better simulation of the shortwave radiation?CSST correlation compared to the short-lead forecasts. Estimation based on the CFS ensemble forecasts indicates that the high-frequency atmospheric variations contribute importantly to the SST variability over the mid-latitude North Pacific during boreal summer. 相似文献
5.
The extratropical response to tropical remote forcing has been examined with so-called tropical ocean-global atmosphere experiments, which use prescribed sea surface temperature (SST) in the tropical Pacific and a slab mixed-layer ocean model elsewhere. In this study we have revisited this experimental design and found that the extratropical response is quite sensitive to the meridional extent of tropical prescribed SST domain. Even in the case of a prescribed annual cycle only (i.e., no ENSO), the differences in the prescribed SST regions lead to different atmospheric motions in the adjacent extratropics. When the tropical forcing includes ENSO, the sensitivity to the meridional domain is more prominent, especially during La Niña events. In La Niña, the prescribed SST is warmer than the simulated SST in the northern subtropics, and the warmer SST differences continue to 30°N. This broad SST differences accompany enhanced atmospheric meridional circulation that directly connects the tropics and extratropics within the Pacific basin. Moreover, the Rossby wave excitation also increases, so the effect of prescribed region difference is felt beyond the Pacific basin. On the other hand, the effect of ENSO sea surface temperature anomalie (i.e., ENSO experiment composite minus control experiment annual cycle, both of which have the same prescribed SST domain) is stronger in the broad tropical forcing experiment. However, the ENSO anomaly composite from own annual cycle is similar regardless of the meridional extent of forcing region, and commonly mimics the Northern Hemisphere El Niño composite of nature in the boreal winter season. 相似文献
6.
LIN Zhong-Da 《大气和海洋科学快报》2010,3(1):40-44
Previous studies have shown that meridional displacement of the East Asian upper-tropospheric jet stream (EAJS) dominates interannual variability of the EAJS in the summer months. This study investigates the tropical Pacific sea surface temperature (SST) anomalies associated with meridional displacement of the monthly EAJS during the summer. The meridional displacement of the EAJS in June is significantly associated with the tropical central Pacific SST anomaly in the winter of previous years, while displacements in July and August are related to tropical eastern Pacific SST anomalies in the late spring and concurrent summer. The EAJS tends to shift southward in the following June (July and August) corresponding to a warm SST anomaly in the central (eastern) Pacific in the winter (late spring-summer). The westerly anomaly south of the Asian jet stream is a result of tropical central Pacific warm SST anomaly-related warming in the tropical troposphere, which is proposed as a possible reason for southward displacement of the EAJS in June. The late spring-summer warm SST anomaly in the tropical eastern Pacific, however, may be linked to southward displacement of the EAJS in July and August through a meridional teleconnection over the western North Pacific (WNP) and East Asia. 相似文献
7.
Atmospheric water vapor content(WVC) is a critical factor for East Asian winter precipitation. This study investigates the dominant modes of interannual variability in WVC over East Asia during winter and their underlying mechanisms.Based on the empirical orthogonal function(EOF) method, the leading mode(EOF1, R~2 = 28.9%) of the interannual variability in the East Asian winter WVC exhibits a meridional dipole pattern characterized by opposite WVC anomalies over northeastern China and eastern China; the second mode(EOF2, R~2 = 24.3%) of the interannual variability in the East Asian winter WVC exhibits a monopole pattern characterized by consistent WVC anomalies over eastern China. EOF1 is mainly modulated by two anomalous zonal water vapor transport(WVT) branches over northeastern China and eastern China, which are associated with an anomalous atmospheric wave train over Eurasia affected by sea ice cover in the Kara Sea-Barents Sea(SIC-KSBS) area in the preceding October-November(ON). EOF2 is mainly modulated by an anomalous westerly WVT branch over eastern China, which is associated with a circumglobal atmospheric zonal wave train in the Northern Hemisphere. This circumglobal zonal wave train is modulated by concurrent central and eastern tropical Pacific sea surface temperature anomalies. The SIC-KSBS anomalies in ON and the concurrent SST anomalies over tropical Pacific may partially account for the interannual variability of EOF1 and EOF2 winter WVC, and thus may provide a theoretical basis for improving the prediction of winter climate over East Asia. 相似文献
8.
Northern Hemisphere circulations differ considerably between individual El Niño-Southern Oscillation events due to internal atmospheric variability and variation in the zonal location of sea surface temperature forcing over the tropical Pacific Ocean. This study examines the similarities between recent Northern Hemisphere droughts associated with La Niña events and anomalously warm tropical west Pacific sea surface temperatures during 1988–1989, 1998–2000, 2007–2008 and 2010–2011 in terms of the hemispheric-scale circulations and the regional forcing of precipitation over North America and Asia during the cold season of November through April. The continental precipitation reductions associated with recent central Pacific La Niña events were most severe over North America, eastern Africa, the Middle East and southwest Asia. High pressure dominated the entire Northern Hemisphere mid-latitudes and weakened and displaced storm tracks northward over North America into central Canada. Regionally over North America and Asia, the position of anomalous circulations within the zonal band of mid-latitude high pressure varied between each La Niña event. Over the northwestern and southeastern United States and southern Asia, the interactions of anomalous circulations resulted in consistent regional temperature advection, which was subsequently balanced by similar precipitation-modifying vertical motions. Over the central and northeastern United States, the spatial variation of anomalous circulations resulted in modest inter-seasonal temperature advection variations, which were balanced by varying vertical motion and precipitation patterns. Over the Middle East and eastern Africa, the divergence of moisture and the advection of dry air due to anomalous circulations enhanced each of the droughts. 相似文献
9.
Impacts of the leading modes of tropical Indian Ocean sea surface temperature anomaly on sub-seasonal evolution of the circulation and rainfall over East Asia during boreal spring and summer 
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下载免费PDF全文 The two leading modes of the interannual variability of the tropical Indian Ocean (TIO) sea surface temperature (SST) anomaly are the Indian Ocean basin mode (IOBM) and the Indian Ocean dipole mode (IODM) from March to August. In this paper, the relationship between the TIO SST anomaly and the sub-seasonal evolution of the circulation and rainfall over East Asia during boreal spring and summer is investigated by using correlation analysis and composite analysis based on multi-source observation data from 1979 to 2013, together with numerical simulations from an atmospheric general circulation model. The results indicate that the impacts of the IOBM on the circulation and rainfall over East Asia vary remarkably from spring to summer. The anomalous anticyclone over the tropical Northwest Pacific induced by the warm IOBM is closely linked with the Pacific–Japan or East Asia–Pacific teleconnection pattern, which persists from March to August. In the upper troposphere over East Asia, the warm phase of the IOBM generates a significant anticyclonic response from March to May. In June and July, however, the circulation response is characterized by enhanced subtropical westerly flow. A distinct anomalous cyclone is found in August. Overall, the IOBM can exert significant influence on the western North Pacific subtropical high, the South Asian high, and the East Asian jet, which collectively modulate the precipitation anomaly over East Asia. In contrast, the effects of the IODM on the climate anomaly over East Asia are relatively weak in boreal spring and summer. Therefore, studying the impacts of the TIO SST anomaly on the climate anomaly in East Asia should take full account of the different sub-seasonal response during boreal spring and summer. 相似文献
10.
Interannual variability of the Guinea Dome and its possible link with the Atlantic Meridional Mode 总被引：1，自引：0，他引：1
Using a high-resolution ocean general circulation model forced by NCEP/NCAR reanalysis data, the interannual variability of the Guinea Dome is studied from a new viewpoint of its possible link with the Atlantic Meridional Mode (AMM), which is related to the meridional migration of the Intertropical Convergence Zone (ITCZ). The dome develops off Dakar seasonally from late spring to late fall owing to the wind-induced Ekman upwelling; its seasonal evolution is associated with the northward migration of the ITCZ. When the ITCZ is located anomalously northward (southward) from late spring to early summer, as a result of the wind-evaporation-sea surface temperature (SST) positive feedback with positive (negative) SST anomaly over the Northern Hemisphere, the dome becomes unusually strong (weak) in fall as a result of stronger (weaker) Ekman upwelling. This may contribute to the decay of the AMM. Thus, the coupled nature between the AMM and the Guinea Dome could be important in understanding, modeling, and predicting the tropical Atlantic variability. 相似文献
11.
通过对COADS1950—1979年海面经向风和海温资料的分析，本文探讨了印度洋—太平洋近赤道地区经向风的长期变化特征及其与厄尼诺发生发展间的关系。结果表明:（1）热带太平洋辐合带系统与海温具有相同的季节变化趋势，冬季赤道辐合带和高海温位于南半球，夏季位于北半球。厄尼诺年经向风发生异常，近赤道地区出现强烈的经向风辐合。（2）近赤道经向风存在准2年（QBO），准3.5年（SO）和准5年（FYO）3种年际低频振荡。QBO对厄尼诺年经向风异常起着重要作用，SO对厄尼诺年和冷水年的经向风变化均十分重要，这两种振荡可以很好的拟合经向风的实际变化，FYO则起着加强的作用。（3）经向风年际低频振荡起源于印度洋—海洋大陆和东太平洋沿岸地区，南北半球冬季风异常和东太平洋沿岸地区信风异常是其主要原因。（4）季风—信风（V）相互作用表现为当异常经向风扰动从季风区东传到信风区时明显增幅，这与信风区海气系统之间时间尺度约1年的自我正反馈有关。 相似文献
12.
Pascal Terray 《Climate Dynamics》2011,36(11-12):2171-2199
The main goal of this paper is to shed additional light on the reciprocal dynamical linkages between mid-latitude Southern Hemisphere climate and the El Ni?o-Southern Oscillation (ENSO) signal. While our analysis confirms that ENSO is a dominant source of interannual variability in the Southern Hemisphere, it is also suggested here that subtropical dipole variability in both the Southern Indian and Atlantic Oceans triggered by Southern Hemisphere mid-latitude variability may also provide a controlling influence on ENSO in the equatorial Pacific. This subtropical forcing operates through various coupled air?Csea feedbacks involving the propagation of subtropical sea surface temperature (SST) anomalies into the deep tropics of the Atlantic and Indian Oceans from boreal winter to boreal spring and a subsequent dynamical atmospheric response to these SST anomalies linking the three tropical basins at the beginning of the boreal spring. This atmospheric response is characterized by a significant weakening of the equatorial Atlantic and Indian Inter-Tropical Convergence Zone (ITCZ). This weakened ITCZ forces an equatorial ??cold Kelvin wave?? response in the middle to upper troposphere that extends eastward from the heat sink regions into the western Pacific. By modulating the vertical temperature gradient and the stability of the atmosphere over the equatorial western Pacific Ocean, this Kelvin wave response promotes persistent zonal wind and convective anomalies over the western equatorial Pacific, which may trigger El Ni?o onset at the end of the boreal winter. These different processes explain why South Atlantic and Indian subtropical dipole time series indices are highly significant precursors of the Ni?o34 SST index several months in advance before the El Ni?o onset in the equatorial Pacific. This study illustrates that the atmospheric internal variability in the mid-latitudes of the Southern Hemisphere may significantly influence ENSO variability. However, this surprising relationship is observed only during recent decades, after the so-called 1976/1977 climate regime shift, suggesting a possible linkage with global warming or decadal fluctuations of the climate system. 相似文献
13.
Global features of the Pacific-Japan Oscillation 总被引：2，自引：0，他引：2
Summary Global features of tropical convection, sea surface temperature (SST) and atmospheric circulation associated with the Pacific-Japan Oscillation (PJO) are examined by using monthly mean global data for 6 years (1979–1984). It is shown that the PJO is not a local phenomena limited to the western-Pacific but related to global-scale atmosphere-ocean variations.The PJO highly correlates with interannual variations of SST in the tropical Pacific. During summers in which positive SST anomaly occurs in the tropical western Pacific, convective activity in the western Pacific especially near Philippines is strongly enhanced but that in the whole equatorial eastern Pacific is greatly suppressed due to negative SST anomaly in these areas.The Walker circulation is intensified in the equatorial Pacific and twin cyclonic cells at 200 mb are generated in the subtropical Pacific of both hemispheres. Strong anticyclonic circulations take place in the northern middle latitudes extending from East China to Northwest Pacific. Anomalous circulations are also generated in the other extratropical regions in the both Northern and Southern Hemispheres.With 7 Figures 相似文献
14.
Freshwater flux (FWF) directly affects sea surface salinity (SSS) and hence modulates sea surface temperature (SST) in the tropical Pacific. This paper quantifies a positive correlation between FWF and SST using observations and simulations of the fifth phase of the Coupled Model Intercomparison Project (CMIP5) to analyze the interannual variability in the tropical Pacific. Comparisons among the displacements of FWF, SSS and SST interannual variabilities illustrate that a large FWF variability is located in the west-central equatorial Pacific, covarying with a large SSS variability, whereas a large SST variability is located in the eastern equatorial Pacific. Most CMIP5 models can reproduce the fact that FWF leads to positive feedback to SST through an SSS anomaly as observed. However, the difference in each model's performance results from different simulation capabilities of the CMIP5 models in the magnitudes and positions of the interannual variabilities, including the mixed layer depth and the buoyancy flux in the equatorial Pacific. SSS anomalies simulated from the CMIP5 multi-model are sensitive to FWF interannual anomalies, which can lead to differences in feedback to interannual SST variabilities. The relationships among the FWF, SSS and SST interannual variabilities can be derived using linear quantitative measures from observations and the CMIP5 multi-model simulations. A 1 mm d-1 FWF anomaly corresponds to an SSS anomaly of nearly 0.12 psu in the western tropical Pacific and a 0.11°C SST anomaly in the eastern tropical Pacific. 相似文献
15.
Coupled ocean-atmosphere surface variability and its climate impacts in the tropical Atlantic region
This study examines time evolution and statistical relationships involving the two leading ocean-atmosphere coupled modes
of variability in the tropical Atlantic and some climate anomalies over the tropical 120 °W–60 °W region using selected historical
files (75-y near global SSTs and precipitation over land), more recent observed data (30-y SST and pseudo wind stress in the
tropical Atlantic) and reanalyses from the US National Centers for Environmental Prediction (NCEP/NCAR) reanalysis System
on the period 1968–1997: surface air temperature, sea level pressure, moist static energy content at 850 hPa, precipitable
water and precipitation. The first coupled mode detected through singular value decomposition of the SST and pseudo wind-stress
data over the tropical Atlantic (30 °N–20 °S) expresses a modulation in the thermal transequatorial gradient of SST anomalies
conducted by one month leading wind-stress anomalies mainly in the tropical north Atlantic during northern winter and fall.
It features a slight dipole structure in the meridional plane. Its time variability is dominated by a quasi-decadal signal
well observed in the last 20–30 ys and, when projected over longer-term SST data, in the 1920s and 1930s but with shorter
periods. The second coupled mode is more confined to the south-equatorial tropical Atlantic in the northern summer and explains
considerably less wind-stress/SST cross-covariance. Its time series features an interannual variability dominated by shorter
frequencies with increased variance in the 1960s and 1970s before 1977. Correlations between these modes and the ENSO-like
Nino3 index lead to decreasing amplitude of thermal anomalies in the tropical Atlantic during warm episodes in the Pacific.
This could explain the nonstationarity of meridional anomaly gradients on seasonal and interannual time scales. Overall the
relationships between the oceanic component of the coupled modes and the climate anomaly patterns denote thermodynamical processes
at the ocean/atmosphere interface that create anomaly gradients in the meridional plane in a way which tends to alter the
north–south movement of the seasonal cycle. This appears to be consistent with the intrinsic non-dipole character of the tropical
Atlantic surface variability at the interannual time step and over the recent period, but produces abnormal amplitude and/or
delayed excursions of the intertropical convergence zone (ITCZ). Connections with continental rainfall are approached through
three (NCEP/NCAR and observed) rainfall indexes over the Nordeste region in Brazil, and the Guinea and Sahel zones in West
Africa. These indices appear to be significantly linked to the SST component of the coupled modes only when the two Atlantic
modes+the ENSO-like Nino3 index are taken into account in the regressions. This suggests that thermal forcing of continental
rainfall is particularly sensitive to the linear combinations of some basic SST patterns, in particular to those that create
meridional thermal gradients. The first mode in the Atlantic is associated with transequatorial pressure, moist static energy
and precipitable water anomaly patterns which can explain abnormal location of the ITCZ particularly in northern winter, and
hence rainfall variations in Nordeste. The second mode is more associated with in-phase variations of the same variables near
the southern edge of the ITCZ, particularly in the Gulf of Guinea during the northern spring and winter. It is primarily linked
to the amplitude and annual phase of the ITCZ excursions and thus to rainfall variations in Guinea. Connections with Sahel
rainfall are less clear due to the difficulty for the model to correctly capture interannual variability over that region
but the second Atlantic mode and the ENSO-like Pacific variability are clearly involved in the Sahel climate interannual fluctuations:
anomalous dry (wet) situations tend to occur when warmer (cooler) waters are present in the eastern Pacific and the gulf of
Guinea in northern summer which contribute to create a northward (southward) transequatorial anomaly gradient in sea level
pressure over West Africa.
Received: 14 April 1998 / Accepted: 24 December 1998 相似文献
16.
C. J. C. Reason 《Meteorology and Atmospheric Physics》1998,69(1-2):49-65
Summary An important pattern of interannual variability in the southern African region is one where sea surface temperature (SST) in neighbouring waters, particularly in the Agulhas Current, its retroflection region and outflow across the southern midlatitudes of the Indian Ocean, is anomalously warm or cool. Evidence exists of significant rainfall anomalies over large parts of southern Africa during these warm or cool SST events. Here, a general circulation model is used to study the response of the atmosphere in the region to an idealised representation of these SST anomalies. The induced atmospheric circulation and precipitation anomalies over the adjacent southern African landmass on intraseasonal through to interannual time scales are investigated.A nonlinear response to the SST anomalies is found in that the changes to the model atmosphere when warm SST forcing is used are not the reverse (in either pattern or magnitude) to that when cold SST forcing is imposed. For the warm SST anomaly, it is found that the atmospheric response is favourable for enhancement of the original SST anomaly on scales up to, and including, annual. However, as the scale becomes interannual (i.e., 15–21 months after imposition of the anomaly), the model response suggests that damping of the original SST anomaly becomes likely. However, no such coherent timescale dependent response is found when the cold SST anomaly is impose. It is suggested that the relationship of the SST anomaly to the background seasonal climatology may help explain this fundamental difference in the response.Examination of the circulation and rainfall patterns under warm SST forcing indicates that there are significant anomalies over large parts of southern Africa on all scales from intraseasonal through to interannual. On the south coast, rainfall anomalies result from enhanced evaporation of moisture off the SST anomaly. Over the interior, changer in the convergence of moist air streams together with suggestions of a shift in the Walker circulations between southern Africa and the bordering tropical South Atlantic and Indian Oceans appear to be associated with the rainfall anomalies. Similar mechanisms of rainfall perturbation are found when the cold SST anomaly is imposed; however, there is a significant response only on intra-annual to interannual scales. In all cases, the magnitude of the rainfall anomalies accumulated over a 90 day season were of the order of 90–180 mm, and therefore represent a significant fraction of the annual total of many areas. These model results re-inforce previous observational work suggesting that SST anomalies south of Africa, particularly in the retroflection region of the Agulhas Current, are linked with significant rainfall anomalies over the adjacent subcontinent.With 12 Figures 相似文献
17.
本文利用1951—1980年逐季的平均值资料(共120个季)讨论了北方涛动和与其相联系的北太平洋海温与北半球海平面气压场、500hPa位势高度场遥相关的基本结构,并与南方涛动和赤道东太平洋海温的结果进行了对比分析.发现北太平洋Namias海区和加利福尼亚海流区海温的变化与北方涛动具有很密切的联系;北方涛动和这两个海区的海温同北半球中高纬度大气环流特别是PNA型和NAO型环流异常存在明显的遥相关关系;南方涛动和赤道太平洋海温同WP型或NPO型环流异常关系比较密切,而与PNA型和NAO型的关系不如北方涛动和Namias海区及加利福尼亚海流区海温的显著. 相似文献
18.
The teleconnection impact of the boreal winter Antarctic Oscillation(AAO) on the Somali Jet(SMJ) intensity in the following spring and summer is examined in this paper.The variability of the boreal winter AAO is positively related to the SMJ intensity in both spring and summer.The analyses show that the SST in southern high and middle latitudes seems to serve as a bridge linking these two systems.When the AAO is in strong positive phase,SST over the Southern Ocean cools in the high latitudes and warms in the middle latitudes,which persists into summer;however,the variability of SST in southern high and middle latitudes is also closely correlated to SMJ intensity.A possible mechanism that links SST variability with the AAO-SMJ relationship is also discussed.The AAO in boreal winter produces an SST anomaly pattern in southern high and middle latitudes through the air-sea coupling.This AAOrelated SST anomaly pattern modulates the local Ferrel cell anomaly in summer,followed by the regional Hadley cell anomaly in tropics.The anomalous vertical motion in tropics then changes the land-sea thermal contrast between the tropical Indian Ocean and the Asian continent through the variability of low cloud cover and downward surface longwave radiation flux.Finally,the land-sea thermal contrast anomaly between the tropical Indian Ocean and the Asian continent changes the SMJ intensity.The results from Community Atmosphere Model experiments forced by the SST anomaly in southern high and middle latitudes also confirm this diagnostic physical process to some extent. 相似文献
19.
Ingo Richter Swadhin K. Behera Takeshi Doi Bunmei Taguchi Yukio Masumoto Shang-Ping Xie 《Climate Dynamics》2014,43(11):3091-3104
The factors controlling equatorial Atlantic winds in boreal spring are examined using both observations and general circulation model (GCM) simulations from the coupled model intercomparison phase 5. The results show that the prevailing surface easterlies flow against the attendant pressure gradient and must therefore be maintained by other terms in the momentum budget. An important contribution comes from meridional advection of zonal momentum but the dominant contribution is the vertical transport of zonal momentum from the free troposphere to the surface. This implies that surface winds are strongly influenced by conditions in the free troposphere, chiefly pressure gradients and, to a lesser extent, meridional advection. Both factors are linked to the patterns of deep convection. Applying these findings to GCM errors indicates, that, consistent with the results of previous studies, the persistent westerly surface wind bias found in most GCMs is due mostly to precipitation errors, in particular excessive precipitation south of the equator over the ocean and deficient precipitation over equatorial South America. Free tropospheric influences also dominate the interannual variability of surface winds in boreal spring. GCM experiments with prescribed climatological sea-surface temperatures (SSTs) indicate that the free tropospheric influences are mostly associated with internal atmospheric variability. Since the surface wind anomalies in boreal spring are crucial to the development of warm SST events (Atlantic Niños), the results imply that interannual variability in the region may rely far less on coupled air–sea feedbacks than is the case in the tropical Pacific. 相似文献
20.
广东省和广西壮族自治区(两广地区)夏季降水时空分布很不均匀,存在显著的年际变化。利用站点观测降水资料、海洋及大气再分析资料,研究了近40 a两广地区夏季降水年际异常与澳大利亚东侧海温异常的联系及机理。在年际时间尺度上,两广夏季降水异常与澳大利亚东侧的海温异常存在显著的负相关关系。当澳大利亚东侧海温异常偏高时,一方面,部分水汽由热带中太平洋向澳大利亚东侧海区辐合,部分沿西太平洋副热带高压边缘向东亚地区输送,两广地区为水汽辐散区域,另一方面,澳大利亚东侧海区的对流活动增强,该地区上空的上升运动异常增强,通过"大气桥"遥相关使得海洋性大陆地区的异常上升运动增强,从而加强了东亚地区的局地Hadley环流,使得两广地区下沉运动增强,二者共同作用致使两广地区夏季干旱少雨;反之亦然。 相似文献