Meridional Teleconnection Research Articles

Asymmetric association of rainfall and atmospheric circulation over East Asia with anomalous rainfall in the tropical western North Pacific in summer

AbstractIt is well known that precipitation anomalies in the tropical western North Pacific (WNP) significantly affect circulation and rainfall in East Asia during summer. In this study, the authors further investigated this relationship, by examining the anomalies associated with positive and negative precipitation anomalies in the tropical WNP. The results suggest these anomalies are asymmetric between the enhanced and suppressed WNP rainfall. Positive precipitation anomalies over the WNP, in comparison with their negative counterparts, are more closely related to the meridional teleconnection pattern and rainfall anomalies along the East Asian rain belt. The implications of the results are discussed.

The impact of boreal autumn SST anomalies over the South Pacific on boreal winter precipitation over East Asia

The possible mechanism behind the variability in the dipole pattern of boreal winter precipitation over East Asia is analyzed in this study. The results show that the SST anomalies (SSTAs) over the South Pacific Ocean (SPO) in boreal autumn are closely related to the variability in the dipole pattern of boreal winter precipitation over East Asia. The physical link between the boreal autumn SPO SSTAs and the boreal winter East Asian precipitation dipole pattern is shown to mainly be the seasonal persistence of the SPO SSTAs themselves. The seasonal persistence of the SPO SSTAs can memorize and transport the signal of the boreal autumn SSTAs to the following winter, and then stimulates a meridional teleconnection pattern from the SH to the NH, resulting in a meridional dipole pattern of atmospheric circulation over East Asia in boreal winter. As a major influencing factor, this dipole pattern of the atmospheric circulation can finally lead to the anomalous precipitation dipole pattern over East Asia in boreal winter. These observed physical processes are further confirmed in this study through numerical simulation. The evidence from this study, showing the impact of the SPO SSTAs in boreal autumn, not only deepens our understanding of the variability in East Asian boreal winter precipitation, but also provides a potentially useful predictor for precipitation in the region.

The mechanism of growth of the low-frequency East Asia–Pacific teleconnection and the triggering role of tropical intraseasonal oscillation

The East Asia–Pacific (EAP) pattern is a well-known meridional teleconnection over East Asia during boreal summer. In this study, the mechanism for growth of the EAP on intraseasonal timescale is investigated through a vorticity budget. It is found that the beta-effect and high-frequency transient eddies have primary contributions to the growth of the low-frequency EAP. The former leads to a westward shift of disturbances associated with the low-frequency EAP and the latter favors an amplification of disturbances, respectively. The interaction between low-frequency disturbances and zonal flow has a damping effect by dragging disturbances eastward. The impact of boreal summer intraseasonal oscillation (BSISO) on the triggering of the low-frequency EAP is also examined in this study based on observational analysis and a linear model experiment. It is shown that an elongated anomalous convection band located in the vicinity of Philippines associated with the dominant mode of BSISO has a significant impact on the initiation of low-frequency EAP via Rossby wave propagation, whereas anomalous convection located over the North Indian Ocean has a limited impact. Based on the results of present study, the low-frequency EAP could be a self-sustained mode, and the BSISO plays a substantial role in triggering the low-frequency EAP.

Physical Mechanism of the Impacts of the Tropical Atlantic Sea Surface Temperature on the Decadal Change of the Summer North Atlantic Oscillation

AbstractIn this study, physical mechanism of the impacts of the tropical Atlantic sea surface temperature (SST) on decadal change of the summer North Atlantic Oscillation (SNAO) was explored using an atmospheric general circulation model (AGCM) developed at the International Centre for Theoretical Physics (ICTP). The simulation results indicate that the decadal warming of the SST over the tropical Atlantic after the late 1970s could have significantly enhanced the convection over the region. This enhanced convection would have strengthened the local meridional circulation over the Eastern Atlantic-North Africa-Western Europe region, exciting a meridional teleconnection. This teleconnection might have brought the signal of the tropical Atlantic SST to the Extratropics, consequently activating the variability of the eastern part of the SNAO southern center, which led to an eastward shift of the SNAO southern center around the late 1970s. Such physical processes are highly consistent with the previous observ...

Physical Mechanisms of Summer Precipitation Variations in the Tarim Basin in Northwestern China

Abstract The Tarim basin (TB) in northwestern China is one of the most arid regions in the middle latitudes, where water is scarce year-round. This study investigates the variations of summer precipitation in the TB and their association with water vapor fluxes and atmospheric circulation. The results suggest that the variations of summer precipitation in the TB are dominated by the water vapor fluxes from the south and east, although the long-term mean water vapor mostly comes from the west. The anomalous water vapor fluxes are closely associated with the meridional teleconnection pattern around 50°–80°E and the zonal teleconnection pattern along the Asian westerly jet in summer. The meridional teleconnection connects central Asia and the tropical Indian Ocean; the zonal teleconnection resembles the “Silk Road pattern.” The two teleconnections lead to negative height anomalies in central Asia and positive height anomalies in the Arabian Sea and India and in northern central China. The anomalous pressure gradient force, caused by these height anomalies, leads to anomalous ascending motion in the TB and brings low-level moisture along the eastern periphery of the Tibetan Plateau and water vapor from the Arabian Sea passing over the Tibetan Plateau to influence precipitation development in the study region.

The Different Configurations of the East Asian Polar Front Jet and Subtropical Jet and the Associated Rainfall Anomalies over Eastern China in Summer

Abstract To investigate the concurrent impacts of the East Asian polar front jet (EAPJ) and subtropical jet (EASJ) on the summer rainfall over eastern China, positive (strengthened EAPJ with weakened EASJ) and negative (weakened EAPJ with strengthened EASJ) configurations are identified. In the positive configuration, rainfall decreases in the northern part of eastern China and increases in the southern part, vice versa in the negative configuration. The possible mechanisms maintaining the two jet configurations are further proposed from the perspectives of sea surface temperature (SST) and synoptic-scale transient eddy activities (STEA). In the positive configuration, meridional distributed cold–warm SST anomalies over the eastern North Pacific may induce regional circulation and meridional temperature gradient anomalies, which can strengthen the EAPJ and weaken the EASJ. The central Pacific La Niña–like SST anomalies are related with the Arctic vortexlike anomalies in the stratosphere, which may strengthen the EAPJ. Furthermore, the divergence of Eliassen–Palm vectors and the conversion from eddy kinetic energy to mean kinetic energy over the active region of the EAPJ may strengthen the EAPJ, vice versa for the weakened EASJ. In the negative configuration, associated with the warm SST anomalies over the western North Pacific, the enhanced convective activities may lead to a strengthened EASJ via meridional teleconnection. The teleconnection may be intensified by the strengthened easterly vertical shear. Additionally, eastern Pacific La Niña–like SST anomalies may intensify the Walker circulation, which may strengthen the EASJ via the Hadley circulation. The STEA-related anomalies are almost opposite those in the positive configuration, especially for the weakened EAPJ.

Interdecadal hydroclimate teleconnections between Asia and North America over the past 600 years

Hydroclimate teleconnections on interdecadal timescale are poorly understood due to the shortness of the instrumental records. We use tree-ring based hydroclimate reconstructions in Asia and North America (NA) to investigate the spatiotemporal evolution of the interdecadal teleconnections over the past 600 years and their associations with coupled ocean–atmosphere patterns. The most dominant interdecadal covarying patterns are the anti-phase hydroclimate change between central Asia and central NA, i.e. the “central Asia–central NA teleconnection”, and the covarying pattern over southwestern (SW) and northeastern (NE) Asia, SW and central NA, i.e. the “SW and NE Asia–SW and central NA teleconnection”. The teleconnections are generally robust except for the cold periods during the Maunder Minimum from the fifteenth century to the end of the sixteenth century and towards the end of the Little Ice Age near the middle nineteenth century. The Asian-Pacific Oscillation (APO) related atmospheric circulations and the westerlies are found to bridge these interdecadal hydroclimate teleconnections. The coupled ocean–atmosphere patterns in the Southern Ocean can modulate the strength of APO related circulations by modulating the Asian summer monsoon and the westerlies via meridional teleconnections. In addition, the wave train from Southern Ocean to Asia may also play an important role on modulating the interdecadal teleconnections.

Spring Indian Ocean-western Pacific SST contrast and the East Asian summer rainfall anomaly

After studying the relationship between SST in the tropical Indian Ocean (TIO), tropical western Pacific (TWP), and tropical eastern Pacific (TEP) and East Asian summer rainfall (EASR), using data provided by NOAA/OAR/ESRL PSD and the National Climate Center of China for the period 1979–2008, an index, SSTDI, was defined to describe the SST difference between the TIO and TWP. In comparison with the winter ENSO, the spring SST contrast between the TIO and TWP was found to be more significantly associated with summer rainfall in East Asia, especially along the EASR band and in Northeast China. This spring SST contrast can persist into summer, resulting in a more significant meridional teleconnection pattern of lower-tropospheric circulation anomalies over the western North Pacific and East Asia. These circulation anomalies are dynamically consistent with the summer rainfall anomaly along the EASR band. When the SSTDI is higher (lower) than normal, the EASR over the Yangtze River valley, Korea, and central and southern Japan is heavier (less) than normal. The present results suggest that this spring SST contrast can be used as a new and better predictor of EASR anomalies.

Evaluation of Multi-Scale Climate Effects on Annual Recruitment Levels of the Japanese Eel, Anguilla japonica, to Taiwan

Long-term (1967–2008) glass eel catches were used to investigate climatic effects on the annual recruitment of Japanese eel to Taiwan. Specifically, three prevailing hypotheses that potentially explain the annual recruitment were evaluated. Hypothesis 1: high precipitation shifts the salinity front northward, resulting in favorable spawning locations. Hypothesis 2: a southward shift of the position of the North Equatorial Current (NEC) bifurcation provides a favorable larval transport route. Hypothesis 3: ocean conditions (eddy activities and productivity) along the larval migration route influence larval survival. Results of time series regression and wavelet analyses suggest that Hypothesis 1 is not supported, as the glass eel catches exhibited a negative relationship with precipitation. Hypothesis 2 is plausible. However, the catches are correlated with the NEC bifurcation with a one-year lag. Considering the time needed for larval transport (only four to six months), the one-year lag correlation does not support the direct transport hypothesis. Hypothesis 3 is supported indirectly by the results. Significant correlations were found between catches and climate indices that affect ocean productivity and eddy activities, such as the Quasi Biennial Oscillation (QBO), North Pacific Gyre Oscillation (NPGO), Pacific Decadal Oscillation (PDO), and Western Pacific Oscillation (WPO). Wavelet analysis reveals three periodicities of eel catches: 2.7, 5.4, and 10.3 years. The interannual coherence with QBO and the Niño 3.4 region suggests that the shorter-term climate variability is modulated zonally by equatorial dynamics. The low-frequency coherence with WPO, PDO, and NPGO demonstrates the decadal modulation of meridional teleconnection via ocean–atmosphere interactions. Furthermore, WPO and QBO are linked to solar activities. These results imply that the Japanese eel recruitment may be influenced by multi-timescale climate variability. Our findings call for investigation of extra-tropical ocean dynamics that affect survival of eels during transport, in addition to the existing efforts to study the equatorial system.

The tropospheric biennial oscillation in the East Asian monsoon region and its influence on the precipitation in China and large‐scale atmospheric circulation in East Asia

AbstractThe precipitation in China manifests a remarkable quasi‐biennial signal. For interannual variability, about 70% stations over China indicate the dominance of a quasi‐2‐year period. The maximum precipitation variability associated with the quasi‐biennial oscillation is located over the Yangtze River valley (YRV) and Huaihe River valley (HRV) as well as South China. This paper attempts to reveal the spatial–temporal evolution of the precipitation in China and related large‐scale atmospheric circulation associated with the tropospheric biennial oscillation (TBO) in East Asia by using a season‐dependent empirical orthogonal function (S‐EOF) analysis approach.The leading two modes of the TBO of summer precipitation in China and associated large‐scale circulations are examined by the S‐EOF analysis and regression analyses based on the S‐EOF time coefficients. The first TBO mode is characterized by an elongated band of positive precipitation anomalies along the YRV and negative precipitation anomalies over both North and South China. The second TBO mode is characterized by an elongated band of positive precipitation anomalies along the HRV and negative precipitation anomalies to the north of the Yellow River and to the south of the Yangtze River, respectively. Meanwhile, the leading modes of the TBO in East Asia may be determined by the meridional teleconnection Rossby wave pattern extending from the WNP to the midlatitudes of East Asia that is forced by the heating source fluctuation over the WNP during boreal summer. And the cold air activity, which is associated with the East Asian winter monsoon, may further influence the leading modes of the TBO through a modulation of the large‐scale atmosphere circulation over East Asia during the following boreal summer.Also found is that the TBO in East Aisa depends on both the large‐scale air–sea coupling over the tropical Indo‐Pacific Ocean regions and the tropical–midlatitude interaction in the western North Pacific (WNP)‐East Asia region. A fundamental element for the TBO in East Asia is the WNP monsoon. It is not only an important component of the TBO cycle in the tropics but also serves as a major source of the TBO signal for the subtropical East Asia. The meridional teleconnection Rossby wave train over the WNP‐East Asia region acts as a conveyer belt that transports the tropical TBO signal to the midlatitudes of East Asia, and produces the TBO footprints in the large‐scale circulation and precipitation in East Asia. Furthermore, the cold air activity over the East Asia during boreal summer also services as an important link in the chain events of the tropical–midlatitude interaction, with enhancing the role of the TBO modes in East Asia. Copyright © 2011 Royal Meteorological Society

Change in early‐summer meridional teleconnection over the western North Pacific and East Asia around the late 1970s

AbstractPrevious studies have shown that during summer there is a meridional teleconnection over the western North Pacific and East Asia (WNP‐EA) on the interannual time scales. This meridional teleconnection is characterized by the zonally elongated circulation anomalies with alternate signs in the meridional direction over this region. The present study indicates that there is a significant change in the early‐summer meridional teleconnection around the late 1970s, by using ERA‐40 reanalysis data during 1958–2001. Although this meridional teleconnection appears as a dominant mode during the whole analysis period, a close inspection revealed that the teleconnection becomes obscure considerably after the late 1970s. Before the late 1970s, the meridional displacement of the East Asian upper‐tropospheric jet stream (EAJS), which is the most dominant mode of EAJS interannual variability, has a statistically significant relationship with both the zonal shift of the WNP subtropical high and rainfall anomaly in the tropical WNP. After the late 1970s, however, this tropical–extratropical interaction over the WNP‐EA is disrupted. We hypothesize that this change in meridional teleconnection is due to the weakening of vertical easterly shear over the tropical WNP in June after the late 1970s. Before the late 1970s, the easterly vertical shear permits the coupling of external mode and internal mode excited by the tropical WNP precipitation anomaly and results in a significant barotropic response, which is necessary for the meridional teleconnection over the WNP‐EA. After the late 1970s, the near‐zero vertical shear is unfavourable for the coupling and thus weakens the meridional teleconnection. Copyright © 2009 Royal Meteorological Society

Mechanisms of Meridional Teleconnection Observed between a Summer Monsoon System and a Subtropical Anticyclone. Part I: The Pacific–Japan Pattern

Abstract Summertime atmospheric circulation over the midlatitude western North Pacific (WNP) is influenced by anomalous convective activity near the Philippines. This meridional teleconnection, observed in monthly anomalies and known as the Pacific–Japan (PJ) pattern, is characterized by zonally elongated cyclonic and anticyclonic anomalies around the enhanced convection center and to its northeast, respectively, in the lower troposphere, with an apparent poleward phase tilt with height. The authors’ idealized two-layer linear model, whose basic state consists of a zonal subtropical jet and a pair of a monsoon system and a subtropical anticyclone, can simulate a PJ-like response against diabatic heating located between the pair. Each of the observed and simulated patterns can gain energy through barotropic and baroclinic conversions from the zonally varying baroclinic mean flow, in an efficiency comparable with that of energy generation due to the anomalous diabatic heating, indicating a characteristic of the pattern as a dry dynamical mode. In fact, the conversion efficiency is sensitive to the location of the anomaly pattern relative to the climatological-mean flow. Furthermore, the second-least damped mode identified in the idealized model bears certain resemblance with the observed PJ pattern, indicating its modal characteristics as well as a critical importance of these features in the mean field for the pattern. In addition to the PJ pattern, another meridional teleconnection pattern with high efficiency for its energy conversion is identified observationally in association with anomalous convection near the Bonin Islands. The anomalous circulation of the PJ pattern, in turn, can intensify the anomalous convective activity near the Philippines through enhancing evaporation and moisture convergence and dynamically inducing anomalous ascent. It is thus hypothesized that the PJ pattern can be regarded as a moist dynamical mode that sustains itself both via dry energy conversion and interaction with moist processes.

Mechanisms of Meridional Teleconnection Observed between a Summer Monsoon System and a Subtropical Anticyclone. Part II: A Global Survey

Abstract A global survey is conducted for atmospheric anomaly patterns of meridional teleconnection over the summer hemisphere associated with anomalous tropical convection. The patterns may be akin to the Pacific–Japan (PJ) teleconnection pattern analyzed in detail in the companion paper. From the survey, meridional teleconnections are identified over five regions, namely, the western North Pacific and Central/North America in boreal summer, as well as the western South Indian Ocean, central South Pacific, and western South Atlantic in austral summer. All of the patterns are observed in the western peripheries of the summertime surface subtropical anticyclones over the individual ocean basins. Although all of the patterns can convert available potential energy (APE) efficiently from the vertically sheared subtropical westerly jets, the efficiencies of barotropic energy conversion from the mean flow and diabatic APE generation differ from one pattern to another. Still, all of the patterns gain energy as the net, to maintain themselves against dissipative processes. Both the anomalous moisture convergence near the surface and the midtropospheric anomalous ascent required for the vorticity and thermal balance act to sustain the anomalous tropical convection, while the wind-evaporation feedback contributes positively only to the PJ pattern over the western North Pacific. Examination of common features and discrepancies among the five teleconnection patterns with respect to their structures and energetics reveals that climatological background features, including the largest horizontal extent of the Asian monsoon system and the North Pacific subtropical anticyclone, in addition to particularly high SST over the Pacific warm pool, render the PJ pattern an outstanding mode of variability.

Role of Subtropical Precipitation Anomalies in Maintaining the Summertime Meridional Teleconnection over the Western North Pacific and East Asia

Abstract The meridional teleconnection patterns over the western North Pacific and East Asia (WNP–EA) during summer have a predominant role in affecting East Asian climate on the interannual time scale. A well-known seesaw pattern of tropical–subtropical precipitation is associated with the meridional teleconnection, and the subtropical precipitation anomaly has been previously viewed as a result of anomalous circulations associated with the teleconnection. In this study, however, the authors suggest that subtropical precipitation anomalies, in turn, can significantly affect large-scale circulations and may be crucial for maintenance of the meridional teleconnection. Diagnosis by using observational and reanalysis data indicates that the meridional teleconnection patterns are clearer in summers when the subtropical rainfall anomalies are greater. The simulated results by a linear baroclinic model indicate that a subtropical heat source, which is equivalent to the diagnosed positive subtropical precipitation anomaly, induces zonally elongated zonal wind anomalies that resemble the diagnosed ones in both the upper and lower troposphere over the extratropical WNP–EA. The simulated results also indicate that the horizontal and vertical structures of circulation responses are insensitive to the locations and shapes of imposed subtropical heat anomalies, which implies the important role of basic flow in circulation responses. This study suggests that, for confidential dynamical seasonal forecasting in East Asia, general circulation models should be required to capture the features of interannual subtropical rainfall variability and basic-state flows in WNP–EA.

A possible mechanism for the co‐variability of the boreal spring Antarctic Oscillation and the Yangtze River valley summer rainfall

AbstractA significant correlation between the boreal spring Antarctic Oscillation (AAO) and the Yangtze River valley summer rainfall (YRVSR) has been found in previous studies, although the mechanisms that might lead to such far‐reaching teleconnection remain unresolved. In this study, one of possible mechanisms responsible for the co‐variability of the boreal spring AAO and the YRVSR is proposed. It follows that the convection activity over the region of the Maritime Continent serves as a bridge linking the boreal spring AAO and the YRVSR. This physical process can be described schematically as follows: during the boreal spring, a positive‐phase (negative‐phase) AAO is concurrent with a strong (weak) convection activity over the region of the Maritime Continent via anomalous meridional circulations along the central South Pacific and two meridional teleconnection wave train patterns, with one over the southern Indian Ocean at the lower level and the other along the central South Pacific at the upper level. Thereafter, the anomalous convection propagates northward along the seasonal cycle, and then changes the western Pacific subtropical high in the following seasons, consequently impacting on the summer rainfall in the Yangtze River valley. Copyright © 2008 Royal Meteorological Society

The ENSO–Asian Monsoon Interaction in a Coupled Ocean–Atmosphere GCM

Abstract In this study, the authors evaluate the (El Niño–Southern Oscillation) ENSO–Asian monsoon interaction in a version of the Hadley Centre coupled ocean–atmosphere general circulation model (CGCM) known as HadCM3. The main focus is on two evolving anomalous anticyclones: one located over the south Indian Ocean (SIO) and the other over the western North Pacific (WNP). These two anomalous anticyclones are closely related to the developing and decaying phases of the ENSO and play a crucial role in linking the Asian monsoon to ENSO. It is found that the HadCM3 can well simulate the main features of the evolution of both anomalous anticyclones and the related SST dipoles, in association with the different phases of the ENSO cycle. By using the simulated results, the authors examine the relationship between the WNP/SIO anomalous anticyclones and the ENSO cycle, in particular the biennial component of the relationship. It is found that a strong El Niño event tends to be followed by a more rapid decay and is much more likely to become a La Niña event in the subsequent winter. The twin anomalous anticyclones in the western Pacific in the summer of a decaying El Niño are crucial for the transition from an El Niño into a La Niña. The El Niño (La Niña) events, especially the strong ones, strengthen significantly the correspondence between the SIO anticyclonic (cyclonic) anomaly in the preceding autumn and WNP anticyclonic (cyclonic) anomaly in the subsequent spring, and favor the persistence of the WNP anomaly from spring to summer. The present results suggest that both El Niño (La Niña) and the SIO/WNP anticyclonic (cyclonic) anomalies are closely tied with the tropospheric biennial oscillation (TBO). In addition, variability in the East Asian summer monsoon, which is dominated by the internal atmospheric variability, seems to be responsible for the appearance of the WNP anticyclonic anomaly through an upper-tropospheric meridional teleconnection pattern over the western and central Pacific.

Simulation of the AAO Anomaly and its Influence on the Northern Hemispheric Circulation in Boreal Winter and Spring

AbstractThe AAO anomaly and its influence on the Northern Hemispheric circulation and temperature over north of Asia are studied by analyzing the output of IAP9L‐AGCM model. First, sea temperature associated with Antarctic Oscillation (AAO) is investigated using the IAP9L‐AGCM model. The model simulation shows the sea temperature at high latitudes in SH may cause the AAO anomaly and the east tropical Pacific ocean is closely related to Pacific Southern America (PSA) teleconnection. Second, the results show that positive AAO tends to enhance Eurasian west wind and circulation anomaly at high latitudes in NH resulting in the increase of both surface temperature (SAT) and temperature at 850hPa over North Asia during the boreal winter and spring. The meridional teleconnection responsible for possible mechanism is pronounced in the simulation. Therefore, model simulation supports our previous observations.

Southern Hemisphere mean zonal wind in upper troposphere and East Asian summer monsoon circulation

Rlationship between the Southern Hemisphere upper troposphere zonal wind variability and the East Asian summer monsoon was studied. The mean zonal wind difference in 150 hPa between 60°S and 30°S is defined as an index (ISH). The research reveals that ISH is negatively correlated with the East Asian summer monsoon (EASM) circulation in the interannual scale. It is also suggested that the meridional teleconnection in the zonal wind field, with the main part in Eastern Hemisphere, from mid-and-high latitudes in the Southern Hemisphere to the tropical region is responsible for the ISH-EASM link-age. The teleconnection may result in changes of the wind fields and pressure system changes causing variability of the East Asian monsoon. In addition, the anomalous teleconnection pattern in Eurasia is likely to be another mechanism. ISH and EASM circulation are found to have both simultaneous and lag correlations, thus, the relationship has implications for seasonal climate prediction over East Asia.

Interannual variability of Antarctic Oscillation and its influence on East Asian climate during boreal winter and spring

The interannual variability of Antarctic Oscillation (AAO) and its influence on East Asian climate during both boreal winter and spring are addressed. The results show that the positive AAO anomaly decreases the cold activity over East Asia during both boreal winter and spring. AAO-related barotropic meridional teleconnection from Antarctic to Arctic is found through analysis of mean meridional circulations. This meridional teleconnection is remarkable over Eurasia during boreal winter and over the Pacific Ocean during boreal spring. The results also show that zonal mean zonal wind at high latitudes in Southern Hemisphere has well positive correlation with that of Eurasia during boreal winter and has negative correlation with Pacific North American teleconnection (PNA) during boreal spring, which again display the meridional teleconnection. Thus, local meridional teleconnection is a possible linkage for interaction of circulations at mid-high latitudes between both hemispheres.

Antarctic oscillation and the dust weather frequency in North China

The linkage between the Antarctic Oscillation (AAO) to the dust weather frequency (DWF) in North China is addressed. Here DWF denotes the number of days of dust weather events including dust haze, blowing dust and dust storm in one year. It is found that the interannual variation of AAO plays a significant role in the dust‐related atmospheric circulation during boreal spring. AAO and DWF correlate well, with positive AAO tending to decrease DWF in North China. Two possible mechanisms for the AAO‐DWF coupling are identified, one is related to a meridional teleconnection pattern; the other is related to a regional circulation pattern over the Pacific Ocean.