This study identified the relationship between tropical cyclone(TC)activity and extreme Pacific–Japan(PJ)teleconnection patterns in August and September.In the East China Sea(ECS)and Mariana Islands(MI)regions,where ...This study identified the relationship between tropical cyclone(TC)activity and extreme Pacific–Japan(PJ)teleconnection patterns in August and September.In the East China Sea(ECS)and Mariana Islands(MI)regions,where the edge of the western North Pacific subtropical high(WNPSH)is located,approximately 60%–75%of TCs migrate to Far East Asian countries.A significant positive correlation existed between the frequency of northward migration of TCs and PJ patterns,since the TC frequency in the ECS and MI regions was significantly higher in the positive compared with the negative phase.In the positive phase,the main reason for the large number of TCs occurring was the monsoon trough’s location and strength.The strong and northeastward-shifted monsoon trough in the positive phase leads to more TCs in the ECS and MI regions.Other large-scale environments associated with TC formation also favored TC genesis around the ECS and MI regions.The higher PDI(power dissipation index)during the positive PJ phase can potentially lead to significant impacts in the Far East Asian countries.These characteristics were particularly more notable in August compared with September.展开更多
By using the one-point correlation method, calculations have been made of the northern early summer 500 hPa teleconnection patterns. Seven teleconnection patterns are revealed, namely, the Western Atlantic (WA), the E...By using the one-point correlation method, calculations have been made of the northern early summer 500 hPa teleconnection patterns. Seven teleconnection patterns are revealed, namely, the Western Atlantic (WA), the Eastern Atlantic (EA), the Eurasian (EU), the Bengal / Northern Pacific (BNP), the Western Pacific (WP), the East Asian / Pacific (EAP), and the Huanghe / East Asian (HEA) patterns. Their centers are determined and their yearly intensity indices (1951-1990) are calculated. On this basis the relationship between their interannual variations and the drought / flood in China is examined. It is noted that the EU, HEA and EAP wave trains are closely related to the drought / flood in China. The HEA and EAP patterns strongly influence the precipitation in eastern China. For example, the fierce floods experienced in 1991 early summer over China are related to the weak EAP and strong HEA patterns.展开更多
In this study, using the ECMWF reanalysis data, the possible linkage between the Pacific-North American teleconnection pattern （PNA） and the North Atlantic Oscillation （NAO） during boreal winter （December- Febru...In this study, using the ECMWF reanalysis data, the possible linkage between the Pacific-North American teleconnection pattern （PNA） and the North Atlantic Oscillation （NAO） during boreal winter （December- February） is investigated. The PNA and the NAO pattern are obtained by performing Rotated Empirical Orthogonal Function （REOF） analysis on an anomalous daily mean 300-hPa geopotential height field. The composite daily NAO indices show that the NAO indices are prone to be negative （positive） when the contemporary PNA indices are extremely positive （negative）. The correlation coefficients between the daily PNA and NAO indices also confirm that, indeed, there is a significant anti-correlation between the PNA and NAO indices. The correlation peaks at a lag of 0 days （meaning contemporary correlation）, and its value is 0.202. Analyses of a newly defined Rossby wave breaking index and diagnostics of the stream function tendency equation indicate that the anti-correlation between PNA and NAO may be caused by the anomalous Rossby wave breaking events associated with the PNA pattern.展开更多
The temporal and spatial characteristics of winter snowfall in the Yangtze–Huaihe River Basin (YHRB) of China and its possible connection with Scandinavian Atmospheric Teleconnection Pattern (SCAND) anomalies are exp...The temporal and spatial characteristics of winter snowfall in the Yangtze–Huaihe River Basin (YHRB) of China and its possible connection with Scandinavian Atmospheric Teleconnection Pattern (SCAND) anomalies are explored based on daily meteorological data contained in the Daily Surface Climate Dataset for China (V3.0) during the period 1960–2012. Results show that winter snowfall in the YHRB exhibits consistent anomalies over the whole region for the interannual variation during 1960–2012. Further analysis suggests that winter snowfall anomalies in the YHRB are closely linked to the anomalous wintertime SCAND activity. When there is more winter snowfall in the YHRB, SCAND is usually in a positive phase, accompanied by a strengthened Urals blocking high and East Asian trough, which is conducive to strengthened cold-air activity, intensified vertical motions, and more water vapor transport in the YHRB. In contrast, less winter snowfall in the YHRB usually happens in the negative phase of SCAND. Our results provide useful information to better understand the relevant mechanism responsible for anomalous winter snowfall in this area.展开更多
Instead of conventional East Asian winter monsoon indices （EAWMIs）, we simply use two large-scale teleconnection patterns to represent long-term variations in the EAWM. First, the Urals blocking pattern index （UBI...Instead of conventional East Asian winter monsoon indices （EAWMIs）, we simply use two large-scale teleconnection patterns to represent long-term variations in the EAWM. First, the Urals blocking pattern index （UBI） is closely related to cold air advection from the high latitudes towards western Siberia, such that it shows an implicit linkage with the Siberian high intensity and the surface air temperature （SAT） variations north of 40°N in the EAWM region. Second, the well-known western Pacific teleconnection index （WPI） is connected with the meridional displacement of the East Asian jet stream and the East Asian trough. This is strongly related to the SAT variations in the coastal area south of 40°N in the EAWM region. The temperature variation in the EAWM region is also represented by the two dominant temperature modes, which are called the northern temperature mode （NTM） and the southern temperature mode （STM）. Compared to 19 existing EAWMIs and other well-known teleconnection patterns, the UBI shows the strongest correlation with the NTM, while the WPI shows an equally strong correlation with the STM as four EAWMIs. The UBI-NTM and WPI-STM relationships are robust when the correlation analysis is repeated by （1） the 31-year running correlation and （2） the 8-year high-pass and low-pass filter. Hence, these results are useful for analyzing the large-scale teleconnections of the EAWM and for evaluating this issue in climate models. Int particular, more studies should focus on the teleconnection patterns over extratropical Eurasia.展开更多
By using a surface air temperature index （SATI） averaged over the eastern Tibetan Plateau （TP）, investigation is conducted on the short-term climate variation associated with the interannual air warming （or cool...By using a surface air temperature index （SATI） averaged over the eastern Tibetan Plateau （TP）, investigation is conducted on the short-term climate variation associated with the interannual air warming （or cooling） over the TP in each summer month. Evidence suggests that the SATI is associated with a consistent teleconnection pattern extending from the TP to central-western Asia and southeastern Europe. Associated rainfall changes include, for a warming case, a drought in northern India in May and June, and a stronger mei-yu front in June. The latter is due to an intensified upper-level northeasterly in eastern China and a wetter and warmer condition over the eastern TP. In the East Asian regions, the time-space distributions of the correlation patterns between SATI and rainfall are more complex and exhibit large differences from month to month. Some studies have revealed a close relationship between the anomalous heating over the TP and the rainfall anomaly along the Yangtze River valley appearing in the summer on a seasonal mean time-scale, whereas in the present study, this relationship only appears in June and the signal＇s significance becomes weaker after the long-term trend in the data was excluded. Close correlations between SATI and the convection activity and SST also occur in the western Pacific in July and August： A zonally-elongated warm tone in the SST in the northwestern Pacific seems to be a passive response of the associated circulation related to a warm SATI. The SATI-associated teleconnection pattern provides a scenario consistently linking the broad summer rainfall anomalies in Europe, central-western Asia, India, and East Asia.展开更多
Based on monthly mean sea level pressure and 500 hPa height data for a 20-year period simulated by IAP 2L AGCM, teleconnection patterns in the Northern Hemisphere appearing in the model are identified and compared wit...Based on monthly mean sea level pressure and 500 hPa height data for a 20-year period simulated by IAP 2L AGCM, teleconnection patterns in the Northern Hemisphere appearing in the model are identified and compared with observations. The results show that almost all of the observed teleconnection patterns in the Northern winter can be reproduced by the model, thus these patterns exist in the atmosphere without any external anomalies. On the other hand, the simulated teleconnection patterns are more dependent on each other than the observed, i.e., they are lack of spatial orthogonality among them, therefore, it is possible that more complex patterns will appear under the action of anomalous external factors. Besides, the simulated teleconnection patterns in summer are greatly different from those in winter, in particular, its scale in summer is much less than that in winter.展开更多
A preferred growing perturbation concept has been introduced into the dynamical study on the generation ofatmospheric teleconnection patterns.It is shown that all the important teleconnection patterns observed in the ...A preferred growing perturbation concept has been introduced into the dynamical study on the generation ofatmospheric teleconnection patterns.It is shown that all the important teleconnection patterns observed in the realatmosphere may be established through internal barotropic dynamical processes.展开更多
The spatial structure and temporal variations of the stationary wave anomalies in the upper troposphere during the Northern Hemisphere winter are studied with the ECMWF data of 1980— 1988 and PCA(principal component ...The spatial structure and temporal variations of the stationary wave anomalies in the upper troposphere during the Northern Hemisphere winter are studied with the ECMWF data of 1980— 1988 and PCA(principal component analysis)method.The vorticity source anomalies of the main teleconnection patterns are analyzed,and their roles in the maintenance of the stationary wave anomaly teleconnection patterns are investigated with the harotropic model.The results show that the anomalies of transient vorticity flux convergences tend to cancel the anomaly of vorticity sources generated by divergent winds.The stationary wave anomaly patterns caused by divergent wind anomalies only are very different from observations.However,if the anomalous transient vorticity flux convergences are also included in the vorticity sources,the simulated patterns will be greatly improved.展开更多
In the extratropics of the Northern Hemisphere, there exist many kinds of atmospheric teleconnection patterns. According to their spatial structure, these teleconnection patterns are generally divided into two groups....In the extratropics of the Northern Hemisphere, there exist many kinds of atmospheric teleconnection patterns. According to their spatial structure, these teleconnection patterns are generally divided into two groups. One group comprises north-south dipole patterns, such as the North Atlantic Oscillation and the North Pacific Oscillation, which have two anomalous centers of opposite signs in the north-south direction. The other group includes the wave train-like patterns, which have several anomalous centers of opposite signs distributed mainly in the zonal direction, such as the Pacific/North American and Eurasian Patterns. These teleconnection patterns greatly impact weather and climate not only in the regions where the teleconnection patterns are active~ but atso in the regions thousands of kilometers away. Studying and understanding the formation mechanisms of these teleconnection patterns form the basis for the short-term climate prediction. This paper reviews advances in the study of the dynamics of these teleconnection patterns, with particular attention paid to the teleconnection patterns that significantly influence the weather and climate of East Asia.展开更多
The variation of the East Asian jet stream （EAJS） associated with the Eurasian （EU） teleconnection pattern is investigated using 60-yr NCEP-NCAR daily reanalysis data over the period 1951-2010.The EAJS consists of...The variation of the East Asian jet stream （EAJS） associated with the Eurasian （EU） teleconnection pattern is investigated using 60-yr NCEP-NCAR daily reanalysis data over the period 1951-2010.The EAJS consists of three components：the polar front jet （PFJ）; the plateau subtropical jet （PSJ）; and the ocean subtropical jet （OSJ）.Of these three jets over East Asia,the EU pattern exhibits a significant influence on the PFJ and OSJ.There is a simultaneous negative correlation between the EU pattern and the PFJ.A significant positive correlation is found between the EU pattern and the OSJ when the EU pattern leads the OSJ by about 5 days.There is no obvious correlation between the EU pattern and the PSJ.The positive EU phase is accompanied by a weakened and poleward-shifted PFJ,which coincides with an intensified OSJ.A possible mechanism for the variation of the EAJS during different EU phases is explored via analyzing the effects of 10-day high-and low-frequency eddy forcing.The zonal wind tendency due to high-frequency eddy forcing contributes to the simultaneous negative correlation between the EU pattern and the PFJ,as well as the northward/southward shift of the PFJ.High-and low-frequency eddy forcing are both responsible for the positive correlation between the EU pattern and the OSJ,but only high-frequency eddy forcing contributes to the lagged variation of the OSJ relative to the EU pattern.The negative correlation between the EU pattern and winter temperature and precipitation anomalies in China is maintained only when the PFJ and OSJ are out of phase with each other.Thus,the EAJS plays an important role in transmitting the EU signal to winter temperature and precipitation anomalies in China.展开更多
The relationship between the variability of the surface elevation of the Greenland Ice Sheet (GIS) in winter and sea level pressure is identified through analysis of data from satellite-borne radar altimeters, togethe...The relationship between the variability of the surface elevation of the Greenland Ice Sheet (GIS) in winter and sea level pressure is identified through analysis of data from satellite-borne radar altimeters, together with meteorological data fields during 1993 2005. We found that both the North Pacific Oscillation (NPO) and the North Atlantic Oscillation (NAO), the two major teleconnection patterns of the atmospheric surface pressure fields in the Northern Hemisphere, significantly influence the GIS winter elevation change. Further, it is suggested that the NPO may affect the GIS accumulation by influencing the NAO, particularly by changing the intensity and location of the Icelandic Low.展开更多
Aim to linking the variability of drought in northwest China to the oceanic influence of North Atlantic SSTs at the background of global warming and at the regional climate change shifting stages, year aridity index v...Aim to linking the variability of drought in northwest China to the oceanic influence of North Atlantic SSTs at the background of global warming and at the regional climate change shifting stages, year aridity index variations in northwest China and summer North Atlantic sea surface temperature （SST） variations are examined for the 44 a period of 1961-2004 using singular value decomposition （SVD） analysis. Results show that the SST anomalies （SSTA）in the North Atlantic in summer reflected three basic models. The first SVD mode of SST pattern shows a dipole - like variation with the positive center located at southwest and negative center at northeast of extratropical North Atlantic. And it strongly relates to the positive trend in AI variation in northwest China. The second coupled modes display the coherent positive anomalies in extratropical North Atlantic SST and the marked opposite trend of AI variability between north and south of Xinjiang. In addition, the lag correlation analysis of the first mode of SSTA and geopotential heights at 500 hPa variations also shows that the indication of the former influencing the latter configuration, which result in higher air temperature and less precipitation when the SSTA in the North Atlantic Ocean in summer motivated Eurasian circulation of EA pattern, further to influence the wet - dry variations in northwest China by the ocean-to - atmosphere forcing.展开更多
Concurrent extreme weather events in geographically distant areas potentially cause high-end risks for societies.By using network analysis,the present study managed to identify significant nearly-simultaneous occurren...Concurrent extreme weather events in geographically distant areas potentially cause high-end risks for societies.By using network analysis,the present study managed to identify significant nearly-simultaneous occurrences of heatwaves between the grid cells in East Asia and Eastern Europe,even though they are geographically far away from each other.By further composite analysis,this study revealed that hot events first occurred in Eastern Europe,typically with a time lag of3-4 days before the East Asian heatwave events.An eastward propagating atmospheric wave train,known as the circumglobal teleconnection(CGT)pattern,bridged the sequent occurrences of extreme events in these two remote regions.Atmospheric blockings,amplified by surface warming over Eastern Europe,not only enhanced local heat extremes but also excited a CGT-like pattern characterized by alternative anomalies of high and low pressures.Subsequent downstream anticyclones in the middle and upper troposphere reduced local cloud cover and increased downward solar radiation,thereby facilitating the formation of heatwaves over East Asia.Nearly half of East Asian heatwave events were preceded by Eastern European heatwave events in the 10-day time range before East Asian heatwave events.This investigation of heatwave teleconnection in the two distant regions exhibits strong potential to improve the prediction accuracy of East Asian heatwaves.展开更多
The interannual variations of summer surface air temperature over Northeast China （NEC） were investigated through a month-to-month analysis from May to August. The results suggested that the warmer temperature over ...The interannual variations of summer surface air temperature over Northeast China （NEC） were investigated through a month-to-month analysis from May to August. The results suggested that the warmer temperature over NEC is related to a local positive 500-hPa geopotential height anomaly for all four months. However, the teleconnection patterns of atmospheric circulation anomalies associated with the monthly surface air temperature over NEC behave as a distinguished subseasonal variation, although the local positive height anomaly is common from month to month. In May and June, the teleconnection pattern is characterized by a wave train in the upper and middle troposphere from the Indian Peninsula to NEC. This wave train is stronger in June than in May, possibly due to the positive feedback between the wave train and the South Asian rainfall anomaly in June, when the South Asian summer monsoon has been established. In July and August, however, the teleconnection pattern associated with the NEC temperature anomalies is characterized by an East Asia/Pacific （EAP） or Pacific/Japan （PJ） pattern, with the existence of precipitation anomalies over the Philippine Sea and the South China Sea. This pattern is much clearer in July corresponding to the stronger convection over the Philippine Sea compared to that in August.展开更多
In this paper,we investigate the influence of the winter NAO on the multidecadal variability of winter East Asian surface air temperature(EASAT)and EASAT decadal prediction.The observational analysis shows that the wi...In this paper,we investigate the influence of the winter NAO on the multidecadal variability of winter East Asian surface air temperature(EASAT)and EASAT decadal prediction.The observational analysis shows that the winter EASAT and East Asian minimum SAT(EAmSAT)display strong in-phase fluctuations and a significant 60-80-year multidecadal variability,apart from a long-term warming trend.The winter EASAT experienced a decreasing trend in the last two decades,which is consistent with the occurrence of extremely cold events in East Asia winters in recent years.The winter NAO leads the detrended winter EASAT by 12-18 years with the greatest significant positive correlation at the lead time of 15 years.Further analysis shows that ENSO may affect winter EASAT interannual variability,but does not affect the robust lead relationship between the winter NAO and EASAT.We present the coupled oceanic-atmospheric bridge(COAB)mechanism of the NAO influences on winter EASAT multidecadal variability through its accumulated delayed effect of~15 years on the Atlantic Multidecadal Oscillation(AMO)and Africa-Asia multidecadal teleconnection(AAMT)pattern.An NAO-based linear model for predicting winter decadal EASAT is constructed on the principle of the COAB mechanism,with good hindcast performance.The winter EASAT for 2020-34 is predicted to keep on fluctuating downward until~2025,implying a high probability of occurrence of extremely cold events in coming winters in East Asia,followed by a sudden turn towards sharp warming.The predicted 2020/21 winter EASAT is almost the same as the 2019/20 winter.展开更多
In this paper,we first review the research advancements in blocking dynamics and highlight the merits and drawbacks of the previous theories of atmospheric blocking.Then,the dynamical mechanisms of atmospheric blockin...In this paper,we first review the research advancements in blocking dynamics and highlight the merits and drawbacks of the previous theories of atmospheric blocking.Then,the dynamical mechanisms of atmospheric blocking are presented based on a nonlinear multi-scale interaction(NMI)model.Previous studies suggested that the eddy deformation(e.g.,eddy straining,wave breaking,and eddy merging)might lead to the formation and maintenance of atmospheric blocking.However,the results were speculative and problematic because the previous studies,based on the time-mean eddy-mean flow interaction model,cannot identify the causal relationship between the evolution of atmospheric blocking and the eddy deformation.Based on the NMI model,we indicate that the onset,growth,maintenance,and decay of atmospheric blocking is mainly produced by the spatiotemporal evolution of pre-existing upstream synoptic-scale eddies,whereas the eddy deformation is a concomitant phenomenon of the blocking formation.The lifetime of blocking is mainly determined by the meridional background potential vorticity gradient(PVy)because a small PVyfavors weak energy dispersion and strong nonlinearity to sustain the blocking.But the zonal movement of atmospheric blocking is associated with the background westerly wind,PVy,and the blocking amplitude.Using this NMI model,a bridge from the climate change to sub-seasonal atmospheric blocking and weather extremes might be established via examining the effect of climate change on PVy.Thus,it is expected that using the NMI model to explore the dynamics of atmospheric blocking and its change is a new direction in the future.展开更多
Investigation is conducted of the interannual variability of the northern Pacific storm track and its concurrent association with 500 hPa height and Pacific sea surface temperature (SST) during winter. Evidence sugges...Investigation is conducted of the interannual variability of the northern Pacific storm track and its concurrent association with 500 hPa height and Pacific sea surface temperature (SST) during winter. Evidence suggests that during the studying period the center of the northern winter Pacific storm track experiences substantial interannual variability in the variation of its latitude, longitude and intensity. Singular value decomposition (SVD) of 15 winter 500 hPa filtered geopotential height variance over the storm track with the tropical and northern Pacific SST shows that the first coupled mode depicts the effect on the track of SSTA over the equatorial central and eastern Pacific, while the second one reflects the impact of Kuroshio SSTA on the track. Further Composite analysis indicates, moreover, that the SSTA over Kuroshio (equatorial central and eastern Pacific) during winter, which is relative to WP (PNA) teleconnection response pattern in 500 hPa height field, respectively, exerts crucial influence on the interannual variability in vigor and meridianal (zonal) displacement of the track over its central and western (eastern) part.展开更多
Experimental outputs of 11 Atmospheric Model Intercomparison Project （AMIP） models from phase 5 of the Coupled Model Intercomparison Project （CMIP5） are analyzed to assess the atmospheric circulation anomaly over ...Experimental outputs of 11 Atmospheric Model Intercomparison Project （AMIP） models from phase 5 of the Coupled Model Intercomparison Project （CMIP5） are analyzed to assess the atmospheric circulation anomaly over Northern Hemisphere induced by the anomalous rainfall over tropical Pacific and Indian Ocean during boreal winter.The analysis shows that the main features of the interannual variation of tropical rainfall anomalies,especially over the Central Pacific （CP） （5°S-5°N,175°E-135°W） and Indo-western Pacific （IWP） （20°S-20°N,110°-150°E） are well captured in all the CMIP5/AMIP models.For the IWP and western Indian Ocean （WIO） （10°S-10°N,45°-75°E）,the anomalous rainfall is weaker in the 11 CMIP5/AMIP models than in the observation.During El Ni（n）o/La Ni（n）a mature phases in boreal winter,consistent with observations,there are geopotential height anomalies known as the Pacific North American （PNA） pattern and Indo-western Pacific and East Asia （IWPEA） pattern in the upper troposphere,and the northwestern Pacific anticyclone （cyclone） （NWPA） in the lower troposphere in the models.Comparison between the models and observations shows that the ability to simulate the PNA and NWPA pattern depends on the ability to simulate the anomalous rainfall over the CP,while the ability to simulate the IWPEA pattern is related to the ability to simulate the rainfall anomaly in the IWP and WIO,as the SST anomaly is same in AMIP experiments.It is found that the tropical rainfall anomaly is important in modeling the impact of the tropical Indo-Pacific Ocean on the extratropical atmospheric circulation anomaly.展开更多
A decadal change in summer rainfall in the Asian inland plateau（AIP） region is identified around 1999. This decadal change is characterized by an abrupt decrease in summer rainfall of about 15.7% of the climatologic...A decadal change in summer rainfall in the Asian inland plateau（AIP） region is identified around 1999. This decadal change is characterized by an abrupt decrease in summer rainfall of about 15.7% of the climatological average amount,leading to prolonged drought in the Asian inland plateau region. Both the surface air temperature and potential evapotranspiration in the AIP show a significant increase, while the soil moisture exhibits a decrease, after the late 1990s. Furthermore,the normalized difference vegetation index shows an apparent decreasing trend during 1999–2007. Three different drought indices—the standardized precipitation index, the standardized precipitation evapotranspiration index, and the self-calibrating Palmer drought severity index—present pronounced climate anomalies during 1999–2007, indicating dramatic drought exacerbation in the region after the late 1990s. This decadal change in the summer rainfall may be attributable to a wave-like teleconnection pattern from Western Europe to Asia. A set of model sensitivity experiments suggests that the summer warming sea surface temperature in the North Atlantic could induce this teleconnection pattern over Eurasia, resulting in recent drought in the AIP region.展开更多
基金the Korea Meteorological Administration Research and Development Program under Grant KMI(Grant No.RS-2023-00241809)conducted under the framework of the research and development program of the Korea Institute of Energy Research(C5-2422).
文摘This study identified the relationship between tropical cyclone(TC)activity and extreme Pacific–Japan(PJ)teleconnection patterns in August and September.In the East China Sea(ECS)and Mariana Islands(MI)regions,where the edge of the western North Pacific subtropical high(WNPSH)is located,approximately 60%–75%of TCs migrate to Far East Asian countries.A significant positive correlation existed between the frequency of northward migration of TCs and PJ patterns,since the TC frequency in the ECS and MI regions was significantly higher in the positive compared with the negative phase.In the positive phase,the main reason for the large number of TCs occurring was the monsoon trough’s location and strength.The strong and northeastward-shifted monsoon trough in the positive phase leads to more TCs in the ECS and MI regions.Other large-scale environments associated with TC formation also favored TC genesis around the ECS and MI regions.The higher PDI(power dissipation index)during the positive PJ phase can potentially lead to significant impacts in the Far East Asian countries.These characteristics were particularly more notable in August compared with September.
基金This study is one of the research projects sponsored by the Monsoon Research Foundation of State Meteorological Administration.
文摘By using the one-point correlation method, calculations have been made of the northern early summer 500 hPa teleconnection patterns. Seven teleconnection patterns are revealed, namely, the Western Atlantic (WA), the Eastern Atlantic (EA), the Eurasian (EU), the Bengal / Northern Pacific (BNP), the Western Pacific (WP), the East Asian / Pacific (EAP), and the Huanghe / East Asian (HEA) patterns. Their centers are determined and their yearly intensity indices (1951-1990) are calculated. On this basis the relationship between their interannual variations and the drought / flood in China is examined. It is noted that the EU, HEA and EAP wave trains are closely related to the drought / flood in China. The HEA and EAP patterns strongly influence the precipitation in eastern China. For example, the fierce floods experienced in 1991 early summer over China are related to the weak EAP and strong HEA patterns.
文摘In this study, using the ECMWF reanalysis data, the possible linkage between the Pacific-North American teleconnection pattern （PNA） and the North Atlantic Oscillation （NAO） during boreal winter （December- February） is investigated. The PNA and the NAO pattern are obtained by performing Rotated Empirical Orthogonal Function （REOF） analysis on an anomalous daily mean 300-hPa geopotential height field. The composite daily NAO indices show that the NAO indices are prone to be negative （positive） when the contemporary PNA indices are extremely positive （negative）. The correlation coefficients between the daily PNA and NAO indices also confirm that, indeed, there is a significant anti-correlation between the PNA and NAO indices. The correlation peaks at a lag of 0 days （meaning contemporary correlation）, and its value is 0.202. Analyses of a newly defined Rossby wave breaking index and diagnostics of the stream function tendency equation indicate that the anti-correlation between PNA and NAO may be caused by the anomalous Rossby wave breaking events associated with the PNA pattern.
基金jointly supported by jointly supported by the National Key Research and Development Program of China(Grant No.2016YFA0600702)the National Natural Science Foundation of China(Grant No.41625019)
文摘The temporal and spatial characteristics of winter snowfall in the Yangtze–Huaihe River Basin (YHRB) of China and its possible connection with Scandinavian Atmospheric Teleconnection Pattern (SCAND) anomalies are explored based on daily meteorological data contained in the Daily Surface Climate Dataset for China (V3.0) during the period 1960–2012. Results show that winter snowfall in the YHRB exhibits consistent anomalies over the whole region for the interannual variation during 1960–2012. Further analysis suggests that winter snowfall anomalies in the YHRB are closely linked to the anomalous wintertime SCAND activity. When there is more winter snowfall in the YHRB, SCAND is usually in a positive phase, accompanied by a strengthened Urals blocking high and East Asian trough, which is conducive to strengthened cold-air activity, intensified vertical motions, and more water vapor transport in the YHRB. In contrast, less winter snowfall in the YHRB usually happens in the negative phase of SCAND. Our results provide useful information to better understand the relevant mechanism responsible for anomalous winter snowfall in this area.
基金supported by Shenzhen Research Project(Grant No.GJHS20120820144245169)the French/Hong Kong Joint Research Project(No.F-HK002/12T)
文摘Instead of conventional East Asian winter monsoon indices （EAWMIs）, we simply use two large-scale teleconnection patterns to represent long-term variations in the EAWM. First, the Urals blocking pattern index （UBI） is closely related to cold air advection from the high latitudes towards western Siberia, such that it shows an implicit linkage with the Siberian high intensity and the surface air temperature （SAT） variations north of 40°N in the EAWM region. Second, the well-known western Pacific teleconnection index （WPI） is connected with the meridional displacement of the East Asian jet stream and the East Asian trough. This is strongly related to the SAT variations in the coastal area south of 40°N in the EAWM region. The temperature variation in the EAWM region is also represented by the two dominant temperature modes, which are called the northern temperature mode （NTM） and the southern temperature mode （STM）. Compared to 19 existing EAWMIs and other well-known teleconnection patterns, the UBI shows the strongest correlation with the NTM, while the WPI shows an equally strong correlation with the STM as four EAWMIs. The UBI-NTM and WPI-STM relationships are robust when the correlation analysis is repeated by （1） the 31-year running correlation and （2） the 8-year high-pass and low-pass filter. Hence, these results are useful for analyzing the large-scale teleconnections of the EAWM and for evaluating this issue in climate models. Int particular, more studies should focus on the teleconnection patterns over extratropical Eurasia.
基金supported by the Key Laboratory of Meteorological Disaster of Ministry of Education (KLME050202 and 050205)the Jiangsu provincial 333 Talent Cultivation Projectthe Jiangsu provincial Qing-Lan Project and the Special Funds for Public Welfare of China [Grant No. GYHY(QX) 2007-6-26]Education Foundation, Hong Kong
文摘By using a surface air temperature index （SATI） averaged over the eastern Tibetan Plateau （TP）, investigation is conducted on the short-term climate variation associated with the interannual air warming （or cooling） over the TP in each summer month. Evidence suggests that the SATI is associated with a consistent teleconnection pattern extending from the TP to central-western Asia and southeastern Europe. Associated rainfall changes include, for a warming case, a drought in northern India in May and June, and a stronger mei-yu front in June. The latter is due to an intensified upper-level northeasterly in eastern China and a wetter and warmer condition over the eastern TP. In the East Asian regions, the time-space distributions of the correlation patterns between SATI and rainfall are more complex and exhibit large differences from month to month. Some studies have revealed a close relationship between the anomalous heating over the TP and the rainfall anomaly along the Yangtze River valley appearing in the summer on a seasonal mean time-scale, whereas in the present study, this relationship only appears in June and the signal＇s significance becomes weaker after the long-term trend in the data was excluded. Close correlations between SATI and the convection activity and SST also occur in the western Pacific in July and August： A zonally-elongated warm tone in the SST in the northwestern Pacific seems to be a passive response of the associated circulation related to a warm SATI. The SATI-associated teleconnection pattern provides a scenario consistently linking the broad summer rainfall anomalies in Europe, central-western Asia, India, and East Asia.
文摘Based on monthly mean sea level pressure and 500 hPa height data for a 20-year period simulated by IAP 2L AGCM, teleconnection patterns in the Northern Hemisphere appearing in the model are identified and compared with observations. The results show that almost all of the observed teleconnection patterns in the Northern winter can be reproduced by the model, thus these patterns exist in the atmosphere without any external anomalies. On the other hand, the simulated teleconnection patterns are more dependent on each other than the observed, i.e., they are lack of spatial orthogonality among them, therefore, it is possible that more complex patterns will appear under the action of anomalous external factors. Besides, the simulated teleconnection patterns in summer are greatly different from those in winter, in particular, its scale in summer is much less than that in winter.
文摘A preferred growing perturbation concept has been introduced into the dynamical study on the generation ofatmospheric teleconnection patterns.It is shown that all the important teleconnection patterns observed in the realatmosphere may be established through internal barotropic dynamical processes.
文摘The spatial structure and temporal variations of the stationary wave anomalies in the upper troposphere during the Northern Hemisphere winter are studied with the ECMWF data of 1980— 1988 and PCA(principal component analysis)method.The vorticity source anomalies of the main teleconnection patterns are analyzed,and their roles in the maintenance of the stationary wave anomaly teleconnection patterns are investigated with the harotropic model.The results show that the anomalies of transient vorticity flux convergences tend to cancel the anomaly of vorticity sources generated by divergent winds.The stationary wave anomaly patterns caused by divergent wind anomalies only are very different from observations.However,if the anomalous transient vorticity flux convergences are also included in the vorticity sources,the simulated patterns will be greatly improved.
基金Supported by the National Natural Science Foundation of China(41025017,41230527,41130962,and 41375060)
文摘In the extratropics of the Northern Hemisphere, there exist many kinds of atmospheric teleconnection patterns. According to their spatial structure, these teleconnection patterns are generally divided into two groups. One group comprises north-south dipole patterns, such as the North Atlantic Oscillation and the North Pacific Oscillation, which have two anomalous centers of opposite signs in the north-south direction. The other group includes the wave train-like patterns, which have several anomalous centers of opposite signs distributed mainly in the zonal direction, such as the Pacific/North American and Eurasian Patterns. These teleconnection patterns greatly impact weather and climate not only in the regions where the teleconnection patterns are active~ but atso in the regions thousands of kilometers away. Studying and understanding the formation mechanisms of these teleconnection patterns form the basis for the short-term climate prediction. This paper reviews advances in the study of the dynamics of these teleconnection patterns, with particular attention paid to the teleconnection patterns that significantly influence the weather and climate of East Asia.
基金supported by the National Natural Science Foundation of China (Grant No. 41130963)the National Basic Research Program of China (973 Program) (Grant No. 2012CB955901)the Jiangsu Collaborative Innovation Center for Climate Change
文摘The variation of the East Asian jet stream （EAJS） associated with the Eurasian （EU） teleconnection pattern is investigated using 60-yr NCEP-NCAR daily reanalysis data over the period 1951-2010.The EAJS consists of three components：the polar front jet （PFJ）; the plateau subtropical jet （PSJ）; and the ocean subtropical jet （OSJ）.Of these three jets over East Asia,the EU pattern exhibits a significant influence on the PFJ and OSJ.There is a simultaneous negative correlation between the EU pattern and the PFJ.A significant positive correlation is found between the EU pattern and the OSJ when the EU pattern leads the OSJ by about 5 days.There is no obvious correlation between the EU pattern and the PSJ.The positive EU phase is accompanied by a weakened and poleward-shifted PFJ,which coincides with an intensified OSJ.A possible mechanism for the variation of the EAJS during different EU phases is explored via analyzing the effects of 10-day high-and low-frequency eddy forcing.The zonal wind tendency due to high-frequency eddy forcing contributes to the simultaneous negative correlation between the EU pattern and the PFJ,as well as the northward/southward shift of the PFJ.High-and low-frequency eddy forcing are both responsible for the positive correlation between the EU pattern and the OSJ,but only high-frequency eddy forcing contributes to the lagged variation of the OSJ relative to the EU pattern.The negative correlation between the EU pattern and winter temperature and precipitation anomalies in China is maintained only when the PFJ and OSJ are out of phase with each other.Thus,the EAJS plays an important role in transmitting the EU signal to winter temperature and precipitation anomalies in China.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX2-YW-Q1-02)the National Basic Research Program of China (973 Program, Grant No. 2009CB421406) and the Nansen Scientific Society in Norway
文摘The relationship between the variability of the surface elevation of the Greenland Ice Sheet (GIS) in winter and sea level pressure is identified through analysis of data from satellite-borne radar altimeters, together with meteorological data fields during 1993 2005. We found that both the North Pacific Oscillation (NPO) and the North Atlantic Oscillation (NAO), the two major teleconnection patterns of the atmospheric surface pressure fields in the Northern Hemisphere, significantly influence the GIS winter elevation change. Further, it is suggested that the NPO may affect the GIS accumulation by influencing the NAO, particularly by changing the intensity and location of the Icelandic Low.
基金The National Natural Science Foundation of China under contract No.904110017
文摘Aim to linking the variability of drought in northwest China to the oceanic influence of North Atlantic SSTs at the background of global warming and at the regional climate change shifting stages, year aridity index variations in northwest China and summer North Atlantic sea surface temperature （SST） variations are examined for the 44 a period of 1961-2004 using singular value decomposition （SVD） analysis. Results show that the SST anomalies （SSTA）in the North Atlantic in summer reflected three basic models. The first SVD mode of SST pattern shows a dipole - like variation with the positive center located at southwest and negative center at northeast of extratropical North Atlantic. And it strongly relates to the positive trend in AI variation in northwest China. The second coupled modes display the coherent positive anomalies in extratropical North Atlantic SST and the marked opposite trend of AI variability between north and south of Xinjiang. In addition, the lag correlation analysis of the first mode of SSTA and geopotential heights at 500 hPa variations also shows that the indication of the former influencing the latter configuration, which result in higher air temperature and less precipitation when the SSTA in the North Atlantic Ocean in summer motivated Eurasian circulation of EA pattern, further to influence the wet - dry variations in northwest China by the ocean-to - atmosphere forcing.
基金Guangdong Major Project of Basic and Applied Basic Research (2020B0301030004)National Natural Science Foundation of China (42275020)+1 种基金Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) (311021001)Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies (2020B1212060025)。
文摘Concurrent extreme weather events in geographically distant areas potentially cause high-end risks for societies.By using network analysis,the present study managed to identify significant nearly-simultaneous occurrences of heatwaves between the grid cells in East Asia and Eastern Europe,even though they are geographically far away from each other.By further composite analysis,this study revealed that hot events first occurred in Eastern Europe,typically with a time lag of3-4 days before the East Asian heatwave events.An eastward propagating atmospheric wave train,known as the circumglobal teleconnection(CGT)pattern,bridged the sequent occurrences of extreme events in these two remote regions.Atmospheric blockings,amplified by surface warming over Eastern Europe,not only enhanced local heat extremes but also excited a CGT-like pattern characterized by alternative anomalies of high and low pressures.Subsequent downstream anticyclones in the middle and upper troposphere reduced local cloud cover and increased downward solar radiation,thereby facilitating the formation of heatwaves over East Asia.Nearly half of East Asian heatwave events were preceded by Eastern European heatwave events in the 10-day time range before East Asian heatwave events.This investigation of heatwave teleconnection in the two distant regions exhibits strong potential to improve the prediction accuracy of East Asian heatwaves.
基金supported by the National Natural Science Foundation of China (Grant No. 41105046)
文摘The interannual variations of summer surface air temperature over Northeast China （NEC） were investigated through a month-to-month analysis from May to August. The results suggested that the warmer temperature over NEC is related to a local positive 500-hPa geopotential height anomaly for all four months. However, the teleconnection patterns of atmospheric circulation anomalies associated with the monthly surface air temperature over NEC behave as a distinguished subseasonal variation, although the local positive height anomaly is common from month to month. In May and June, the teleconnection pattern is characterized by a wave train in the upper and middle troposphere from the Indian Peninsula to NEC. This wave train is stronger in June than in May, possibly due to the positive feedback between the wave train and the South Asian rainfall anomaly in June, when the South Asian summer monsoon has been established. In July and August, however, the teleconnection pattern associated with the NEC temperature anomalies is characterized by an East Asia/Pacific （EAP） or Pacific/Japan （PJ） pattern, with the existence of precipitation anomalies over the Philippine Sea and the South China Sea. This pattern is much clearer in July corresponding to the stronger convection over the Philippine Sea compared to that in August.
基金supported by the National Natural Science Foundation of China(NSFC)Project(Grant No.41790474)Shandong Natural Science Foundation Project(Grant No.ZR2019ZD12)Fundamental Research Funds for the Central Universities(Grant No.201962009).
文摘In this paper,we investigate the influence of the winter NAO on the multidecadal variability of winter East Asian surface air temperature(EASAT)and EASAT decadal prediction.The observational analysis shows that the winter EASAT and East Asian minimum SAT(EAmSAT)display strong in-phase fluctuations and a significant 60-80-year multidecadal variability,apart from a long-term warming trend.The winter EASAT experienced a decreasing trend in the last two decades,which is consistent with the occurrence of extremely cold events in East Asia winters in recent years.The winter NAO leads the detrended winter EASAT by 12-18 years with the greatest significant positive correlation at the lead time of 15 years.Further analysis shows that ENSO may affect winter EASAT interannual variability,but does not affect the robust lead relationship between the winter NAO and EASAT.We present the coupled oceanic-atmospheric bridge(COAB)mechanism of the NAO influences on winter EASAT multidecadal variability through its accumulated delayed effect of~15 years on the Atlantic Multidecadal Oscillation(AMO)and Africa-Asia multidecadal teleconnection(AAMT)pattern.An NAO-based linear model for predicting winter decadal EASAT is constructed on the principle of the COAB mechanism,with good hindcast performance.The winter EASAT for 2020-34 is predicted to keep on fluctuating downward until~2025,implying a high probability of occurrence of extremely cold events in coming winters in East Asia,followed by a sudden turn towards sharp warming.The predicted 2020/21 winter EASAT is almost the same as the 2019/20 winter.
基金supported by the National Natural Science Foundation of China(Grant Nos.42150204 and 42288101)the Chinese Academy of Sciences Strategic Priority Research Program(Grant No.XDA19070403)。
文摘In this paper,we first review the research advancements in blocking dynamics and highlight the merits and drawbacks of the previous theories of atmospheric blocking.Then,the dynamical mechanisms of atmospheric blocking are presented based on a nonlinear multi-scale interaction(NMI)model.Previous studies suggested that the eddy deformation(e.g.,eddy straining,wave breaking,and eddy merging)might lead to the formation and maintenance of atmospheric blocking.However,the results were speculative and problematic because the previous studies,based on the time-mean eddy-mean flow interaction model,cannot identify the causal relationship between the evolution of atmospheric blocking and the eddy deformation.Based on the NMI model,we indicate that the onset,growth,maintenance,and decay of atmospheric blocking is mainly produced by the spatiotemporal evolution of pre-existing upstream synoptic-scale eddies,whereas the eddy deformation is a concomitant phenomenon of the blocking formation.The lifetime of blocking is mainly determined by the meridional background potential vorticity gradient(PVy)because a small PVyfavors weak energy dispersion and strong nonlinearity to sustain the blocking.But the zonal movement of atmospheric blocking is associated with the background westerly wind,PVy,and the blocking amplitude.Using this NMI model,a bridge from the climate change to sub-seasonal atmospheric blocking and weather extremes might be established via examining the effect of climate change on PVy.Thus,it is expected that using the NMI model to explore the dynamics of atmospheric blocking and its change is a new direction in the future.
基金Sponsored by the China National Key Fundamental Research and Development Program(G1998040901-3) and National Natural Science F
文摘Investigation is conducted of the interannual variability of the northern Pacific storm track and its concurrent association with 500 hPa height and Pacific sea surface temperature (SST) during winter. Evidence suggests that during the studying period the center of the northern winter Pacific storm track experiences substantial interannual variability in the variation of its latitude, longitude and intensity. Singular value decomposition (SVD) of 15 winter 500 hPa filtered geopotential height variance over the storm track with the tropical and northern Pacific SST shows that the first coupled mode depicts the effect on the track of SSTA over the equatorial central and eastern Pacific, while the second one reflects the impact of Kuroshio SSTA on the track. Further Composite analysis indicates, moreover, that the SSTA over Kuroshio (equatorial central and eastern Pacific) during winter, which is relative to WP (PNA) teleconnection response pattern in 500 hPa height field, respectively, exerts crucial influence on the interannual variability in vigor and meridianal (zonal) displacement of the track over its central and western (eastern) part.
基金supported by the Ministry of Science and Technology of China (National Basic Research Program of China Grant No. 2012CB955602)the National Natural Science Foundation of China (Grant Nos. 41176006 and 41221063)
文摘Experimental outputs of 11 Atmospheric Model Intercomparison Project （AMIP） models from phase 5 of the Coupled Model Intercomparison Project （CMIP5） are analyzed to assess the atmospheric circulation anomaly over Northern Hemisphere induced by the anomalous rainfall over tropical Pacific and Indian Ocean during boreal winter.The analysis shows that the main features of the interannual variation of tropical rainfall anomalies,especially over the Central Pacific （CP） （5°S-5°N,175°E-135°W） and Indo-western Pacific （IWP） （20°S-20°N,110°-150°E） are well captured in all the CMIP5/AMIP models.For the IWP and western Indian Ocean （WIO） （10°S-10°N,45°-75°E）,the anomalous rainfall is weaker in the 11 CMIP5/AMIP models than in the observation.During El Ni（n）o/La Ni（n）a mature phases in boreal winter,consistent with observations,there are geopotential height anomalies known as the Pacific North American （PNA） pattern and Indo-western Pacific and East Asia （IWPEA） pattern in the upper troposphere,and the northwestern Pacific anticyclone （cyclone） （NWPA） in the lower troposphere in the models.Comparison between the models and observations shows that the ability to simulate the PNA and NWPA pattern depends on the ability to simulate the anomalous rainfall over the CP,while the ability to simulate the IWPEA pattern is related to the ability to simulate the rainfall anomaly in the IWP and WIO,as the SST anomaly is same in AMIP experiments.It is found that the tropical rainfall anomaly is important in modeling the impact of the tropical Indo-Pacific Ocean on the extratropical atmospheric circulation anomaly.
基金supported jointly by the National Key Research and Development Program(Grant No.2016YFA0600604)the National Natural Science Foundation of China(Grant No.41461144001 and 41375046)+1 种基金Open Research Fund Program of Key Laboratory of Meteorological Disaster of Ministry of Education(Nanjing University of Information Science and Technology)Grant No.KLME1403the Chinese Academy of Sciences President’s International Fellowship Initiative
文摘A decadal change in summer rainfall in the Asian inland plateau（AIP） region is identified around 1999. This decadal change is characterized by an abrupt decrease in summer rainfall of about 15.7% of the climatological average amount,leading to prolonged drought in the Asian inland plateau region. Both the surface air temperature and potential evapotranspiration in the AIP show a significant increase, while the soil moisture exhibits a decrease, after the late 1990s. Furthermore,the normalized difference vegetation index shows an apparent decreasing trend during 1999–2007. Three different drought indices—the standardized precipitation index, the standardized precipitation evapotranspiration index, and the self-calibrating Palmer drought severity index—present pronounced climate anomalies during 1999–2007, indicating dramatic drought exacerbation in the region after the late 1990s. This decadal change in the summer rainfall may be attributable to a wave-like teleconnection pattern from Western Europe to Asia. A set of model sensitivity experiments suggests that the summer warming sea surface temperature in the North Atlantic could induce this teleconnection pattern over Eurasia, resulting in recent drought in the AIP region.
