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Wen Chen - One of the best experts on this subject based on the ideXlab platform.
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diverse influences of spring Arctic Oscillation on the following winter el nino southern Oscillation in cmip5 models
Climate Dynamics, 2021Co-Authors: Yuqiong Zheng, Shangfeng Chen, Wen ChenAbstract:This study evaluates the ability of 35 climate models, which participate in the Coupled Model Intercomparison Project Phase 5 (CMIP5) historical climate simulations, in reproducing the connection between boreal spring Arctic Oscillation (AO) and its following winter El Nino–Southern Oscillation (ENSO). The spring AO–winter ENSO correlations range from − 0.41 to 0.44 among the 35 models for the period of 1958–2005. Ensemble means of the models with positive and negative AO–ENSO correlations both show strong spring sea surface temperature (SST) cooling in the subtropical North Pacific during a positive phase of spring AO, which is conducive to occurrence of a La Nina event in the following winter. However, the models with positive AO–ENSO relations produce a pronounced spring cyclonic anomaly over the subtropical northwestern Pacific and westerly anomalies over the tropical western Pacific (TWP). These westerly wind anomalies bring SST warming and positive precipitation anomalies in the tropical central-eastern Pacific (TCEP) during the following summer, which would maintain and develop into the following winter that support an El Nino-like pattern in the TCEP via a positive air-sea feedback mechanism. By contrast, the models with negative AO–ENSO connections fail to reproduce the spring AO-related cyclonic anomaly over the subtropical northwestern Pacific and westerly wind anomalies in the TWP. Thus, these models would produce a La Nina-like pattern in the subsequent winter. Difference in the spring AO-associated atmospheric anomalies over the subtropical North Pacific among the CMIP5 models may be attributed to biases of the models in simulating the spring climatological storm track.
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impacts of the atlantic multidecadal Oscillation on the relationship of the spring Arctic Oscillation and the following east asian summer monsoon
Journal of Climate, 2020Co-Authors: Shangfeng Chen, Wen Chen, Linye SongAbstract:AbstractPrevious studies indicated that spring Arctic Oscillation (AO) can influence the following East Asian summer monsoon (EASM). This study reveals that the Atlantic Multidecadal Oscillation (A...
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multidecadal changes in the influence of the Arctic Oscillation on the east asian surface air temperature in boreal winter
Algorithmic Approaches for Transportation Modeling Optimization and Systems, 2019Co-Authors: Hainan Gong, Lin Wang, Wen ChenAbstract:The time-varying influences of the wintertime Arctic Oscillation (AO) on the concurrent East Asian surface air temperature (EAT) are investigated based on JRA-55 reanalysis data. Results reveal that there are multidecadal variations in the influences of wintertime AO on the EAT during 1958–2018. Before the mid-1980s, the impact of winter AO on the simultaneous EAT is weak and confined northward of 40° N over East Asia. After the mid-1980s, by contrast, the winter AO’s influence is stronger and can extend southward of 25° N over East Asia. The multidecadal variations of the winter AO–EAT relationship are mainly modulated by the magnitudes of the North Pacific center of the winter AO. During the periods with strong North Pacific center of the winter AO, in association with the positive phase of the winter AO, the low-level southeasterly anomalies on the west side of the anticyclone over North Pacific bring warm air from the ocean to East Asia and lead to a significant winter AO–EAT relationship. In contrast, the southerly anomalies are weak and even reversed to northerly over the coast of East Asia during the periods with weak North Pacific center of winter AO, which confines the influence of winter AO on northern East Asia and lead to an insignificant winter AO–EAT relationship. Our finding provides new insight into the understanding of the decadal changes of AO’s impacts on the regional climate.
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enhanced impact of Arctic sea ice change during boreal autumn on the following spring Arctic Oscillation since the mid 1990s
Climate Dynamics, 2019Co-Authors: Shangfeng Chen, Wen ChenAbstract:Previous study indicated that changes in the Arctic sea ice concentration (ASIC) during boreal autumn in the Laptev-eastern Siberian-Beaufort Seas have a marked influence on the interannual variation of Arctic Oscillation (AO) during following spring. This study reveals a pronounced enhancement of the linkage between autumn ASIC changes and following spring AO since the mid-1990s. The correlation coefficient between the autumn ASIC and spring AO index reaches 0.72 during 1998–2014. During this period, autumn ASIC decrease results in pronounced tropospheric warming over the high latitudes and a reduction of meridional temperature gradient. This leads to decrease in circumpolar westerly winds and increase in the upward propagation of quasi-stationary wave, which weakens stratospheric polar vortex. Then, spring AO becomes weaker than normal via the interaction between stationary wave and mean flow and the accompanying downward propagation of anomalous easterly winds. Before the mid-1990s, however, decrease in the autumn ASIC is not followed by an obvious change in the overlying air temperature. Accordingly, circumpolar westerly winds and polar vortex experience weak changes. Thus, the linkage between the autumn ASIC and following spring AO is weak. It is suggested that interdecadal change in the impact of autumn ASIC on the spring AO is attributed to a change in the interannual variability of autumn ASIC. Specifically, interannual variability of autumn ASIC is much larger after the mid-1990s, which contributes to stronger stratospheric response and ASIC-spring AO connection.
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Diversity of the Wintertime Arctic Oscillation Pattern among CMIP5 Models: Role of the Stratospheric Polar Vortex
Journal of Climate, 2019Co-Authors: Hainan Gong, Lin Wang, Wen Chen, Wen Zhou, Lin Liu, Debashis Nath, Xiaoqing LanAbstract:AbstractThe wintertime Arctic Oscillation (AO) pattern in phase 5 of the Coupled Model Intercomparison Project (CMIP5) climate models displays notable differences from the reanalysis. The North Pac...
Shangfeng Chen - One of the best experts on this subject based on the ideXlab platform.
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diverse influences of spring Arctic Oscillation on the following winter el nino southern Oscillation in cmip5 models
Climate Dynamics, 2021Co-Authors: Yuqiong Zheng, Shangfeng Chen, Wen ChenAbstract:This study evaluates the ability of 35 climate models, which participate in the Coupled Model Intercomparison Project Phase 5 (CMIP5) historical climate simulations, in reproducing the connection between boreal spring Arctic Oscillation (AO) and its following winter El Nino–Southern Oscillation (ENSO). The spring AO–winter ENSO correlations range from − 0.41 to 0.44 among the 35 models for the period of 1958–2005. Ensemble means of the models with positive and negative AO–ENSO correlations both show strong spring sea surface temperature (SST) cooling in the subtropical North Pacific during a positive phase of spring AO, which is conducive to occurrence of a La Nina event in the following winter. However, the models with positive AO–ENSO relations produce a pronounced spring cyclonic anomaly over the subtropical northwestern Pacific and westerly anomalies over the tropical western Pacific (TWP). These westerly wind anomalies bring SST warming and positive precipitation anomalies in the tropical central-eastern Pacific (TCEP) during the following summer, which would maintain and develop into the following winter that support an El Nino-like pattern in the TCEP via a positive air-sea feedback mechanism. By contrast, the models with negative AO–ENSO connections fail to reproduce the spring AO-related cyclonic anomaly over the subtropical northwestern Pacific and westerly wind anomalies in the TWP. Thus, these models would produce a La Nina-like pattern in the subsequent winter. Difference in the spring AO-associated atmospheric anomalies over the subtropical North Pacific among the CMIP5 models may be attributed to biases of the models in simulating the spring climatological storm track.
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impacts of the atlantic multidecadal Oscillation on the relationship of the spring Arctic Oscillation and the following east asian summer monsoon
Journal of Climate, 2020Co-Authors: Shangfeng Chen, Wen Chen, Linye SongAbstract:AbstractPrevious studies indicated that spring Arctic Oscillation (AO) can influence the following East Asian summer monsoon (EASM). This study reveals that the Atlantic Multidecadal Oscillation (A...
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enhanced impact of Arctic sea ice change during boreal autumn on the following spring Arctic Oscillation since the mid 1990s
Climate Dynamics, 2019Co-Authors: Shangfeng Chen, Wen ChenAbstract:Previous study indicated that changes in the Arctic sea ice concentration (ASIC) during boreal autumn in the Laptev-eastern Siberian-Beaufort Seas have a marked influence on the interannual variation of Arctic Oscillation (AO) during following spring. This study reveals a pronounced enhancement of the linkage between autumn ASIC changes and following spring AO since the mid-1990s. The correlation coefficient between the autumn ASIC and spring AO index reaches 0.72 during 1998–2014. During this period, autumn ASIC decrease results in pronounced tropospheric warming over the high latitudes and a reduction of meridional temperature gradient. This leads to decrease in circumpolar westerly winds and increase in the upward propagation of quasi-stationary wave, which weakens stratospheric polar vortex. Then, spring AO becomes weaker than normal via the interaction between stationary wave and mean flow and the accompanying downward propagation of anomalous easterly winds. Before the mid-1990s, however, decrease in the autumn ASIC is not followed by an obvious change in the overlying air temperature. Accordingly, circumpolar westerly winds and polar vortex experience weak changes. Thus, the linkage between the autumn ASIC and following spring AO is weak. It is suggested that interdecadal change in the impact of autumn ASIC on the spring AO is attributed to a change in the interannual variability of autumn ASIC. Specifically, interannual variability of autumn ASIC is much larger after the mid-1990s, which contributes to stronger stratospheric response and ASIC-spring AO connection.
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Recent weakening of the linkage between the spring Arctic Oscillation and the following winter El Niño-Southern Oscillation
Climate Dynamics, 2019Co-Authors: Shangfeng Chen, Renguang Wu, Bin YuAbstract:Previous studies indicated that the spring Arctic Oscillation (AO) is an important extratropical forcing of the occurrence of El Niño-Southern Oscillation (ENSO) in the following winter. This study reveals an interdecadal weakening in the spring AO-winter ENSO connection around the early-1990s and investigates the reason of this change. Before the early-1990s, in association with the positive phase of the spring AO, an anomalous anticyclone appears over the mid-latitude North Pacific, accompanied by an anomalous cyclone over the subtropical North Pacific that is supported by the wave-mean flow interaction. Correspondingly, the sea surface temperature (SST) warming and its associated positive precipitation anomalies develop over the subtropical North Pacific, which play a crucial role in forming and maintaining the westerly wind anomalies over the tropical western Pacific (TWP) from spring to the following summer. The TWP westerly wind anomalies would induce the El Niño event in the following winter. After the early-1990s, by contrast, the Pacific component of the circulation anomalies related to the spring AO is weak and shifts northward. This is followed by weak anomalies of SST and precipitation over the subtropical North Pacific, as well as weak TWP westerly wind anomalies from spring to the following summer. Hence, the spring AO-winter ENSO connection is weak after the early-1990s. The change of the spring AO associated circulation anomalies over the North Pacific around the early-1990s tends to be related to the interdecadal change in the intensity of the Aleutian Low.
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Performance of the CMIP5 models in simulating the Arctic Oscillation during boreal spring
Climate Dynamics, 2019Co-Authors: Shangfeng Chen, Renguang Wu, Linye SongAbstract:This study evaluates the performance of thirty coupled models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) in capturing the Arctic Oscillation (AO) during boreal spring. We focus on model’s ability in simulating spring AO’s spatial structure, dominant temporal frequencies and climatic impacts. The anomalous anticyclone over the North Pacific and the North Atlantic in the positive spring AO phase is much stronger in most of the models than in the observations. This may be due to that most models simulate a stronger interannual variability of atmospheric anomalies over the North Pacific and North Atlantic. In addition, the center of the anomalous anticyclone over the North Pacific in the MME shifts obviously southeastward and that over the North Atlantic shift northeastward compared to the observations. Inter-model longitudinal spread is larger than the latitudinal spread in the anomalous anticyclone center over both the North Pacific and North Atlantic. Most of the models produce periods longer than the observed 4-year spectral peak in spring AO index. In addition, the model’s ability in reproducing the vertical structure of zonal wind tends to have a close relation with the model’s performance in capturing the vertical structure of air temperature related to the spring AO. Furthermore, there exist larger spreads among the models in simulating the spring AO-related surface air temperature over the Russian Far East and the west coast of North America. These spreads were partly related to the biases of the models in capturing the atmospheric circulation anomalies related to the Pacific center of the spring AO.
Huijun Wang - One of the best experts on this subject based on the ideXlab platform.
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recent intensified impact of december Arctic Oscillation on subsequent january temperature in eurasia and north africa
Climate Dynamics, 2019Co-Authors: Huijun Wang, Yongqi GaoAbstract:This study reveals an intensified influence of December Arctic Oscillation (AO) on the subsequent January surface air temperature (SAT) over Eurasia and North Africa in recent decades. The connection is statistically insignificant during 1957/58–1979/80 (P1), which becomes statistically significant during 1989/90–2011/12 (P2). The possible causes are further investigated. Associated with positive December AO during P2, significant anomalous anticyclone emerges over the central North Atlantic, which is accompanied with significant westerly and easterly anomalies along 45°−65°N and 20°−40°N, respectively. This favors the significant influence of December AO on the subsequent January SAT and atmospheric circulation over Eurasia and North Africa via triggering the North Atlantic tripole sea surface temperature (SST) anomaly that persists into the subsequent January. By contrast, the December AO-related anomalous anticyclone during P1 is weak and is characterized by two separate centers located in the eastern and western North Atlantic. Correspondingly, the westerly and easterly anomalies over the North Atlantic Ocean are weak and the-related tripole SST anomaly is not well formed, unfavorable for the persistent impact of the December AO into the subsequent January. Further analyses indicate that the different anomalous anticyclone associated with the December AO over the North Atlantic may be induced by the strengthened synoptic-scale eddy feedbacks over the North Atlantic, which may be related to the interdecadal intensification of the storm track activity. Additionally, the planetary stationary wave related to the December AO propagates from surface into upper stratosphere at mid-latitudes during P2, which further propagates downward to the troposphere and causes anomalous atmospheric circulation in the subsequent January.
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unstable relationship between the Arctic Oscillation and east asian jet stream in winter and possible mechanisms
Theoretical and Applied Climatology, 2019Co-Authors: Yang Liu, Huijun Wang, Yali ZhuAbstract:Based on long-term reanalysis datasets, this study revealed that the relationship between the Arctic Oscillation (AO) and the East Asian jet stream (EAJS) is significant negative during 1925–1945 and 1985–2005 (significant periods; hereafter SPs) whereas insignificant during 1900–1920 and 1955–1975 (insignificant periods; ISPs). The unstable AO-EAJS relationship might be related to the interdecadal change of AO’s spatial structure. During SPs winters, anomalous positive AO events are characterized by atmospheric negative anomalies in the Arctic with two anomalous positive centers located in the extratropical Atlantic and Pacific, exhibiting a quasi-barotropic structure. By contrast, the anomalous center in the North Pacific is barely observed during ISPs winters. Further analysis indicated that such interdecadal change might be attributed to change of troposphere-stratosphere coupling and the North Pacific air-sea interaction. On the one hand, anomalous AO at surface is closely related to obvious planetary waves downward from the stratosphere during SPs, which favors the subtropics-Arctic teleconnection. On the other hand, the Interdecadal Pacific Oscillation (IPO) shows warm phase during SPs, which induces larger variance of the Aleutian Low and more intensive divergence anomalies at upper level troposphere. Due to the advection of vorticity induced by stronger divergence is favorable for stronger Rossby wave source, the Rossby wave activity is much stronger and could further propagate eastward to the North Atlantic during SPs, resulting in the Pacific-Atlantic teleconnection. Such a mechanism is supported by the numerical simulations from two individual models that are perturbed by warm/cold IPO sea surface temperature anomalies.
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simulated and projected relationship between the east asian winter monsoon and winter Arctic Oscillation in cmip5 models
Atmospheric and Oceanic Science Letters, 2018Co-Authors: L I Shuo, H E Shengping, L I Fei, Huijun WangAbstract:Interdecadal change in the relationship between the East Asian winter monsoon (EAWM) and the Arctic Oscillation (AO) has been documented by many studies. This study, utilizing the model outputs fro...
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interdecadal change between the Arctic Oscillation and east asian climate during 1900 2015 winters
International Journal of Climatology, 2017Co-Authors: Yang Liu, Huijun Wang, Yali ZhuAbstract:Using the ERA-20th century reanalysis data for the period 1900–2009 and NCEP/NCAR reanalysis data for the period 1948–2016, this work inspects the interdecadal variations between Arctic Oscillation (AO) and the surface air temperature (SAT) in East Asia, then investigates possible mechanisms, and finally considers a recent switch of the AO–SAT relationship. It is revealed that the AO–SAT relationship is statistically significant during 1928–1948 and 1975–1995. It means that positive AO is associated with significant weakening of the sea level pressure (SLP) gradient over East Asia, East Asian trough, and East Asian jet stream. However, the AO–SAT relationship is statistically insignificant and there is little significance in the AO-related circulation during 1905–1925 and 1950–1970. Further examination revealed that the unstable AO–SAT relationship might be attributable to the interdecadal change of AO's Azores center. During 1928–1948/1975–1995 winters, the SLP anomalies of Azores high in the positive phase of AO are robust and lead to upper-level convergence anomalies, which can induce obvious significant Rossby wave source (RWS) anomalies over the Mediterranean and northeastern Atlantic. During 1905–1925/1950–1970, however, the SLP anomalies of Azores high in the positive AO phase become weaker. As a result, the convergence and RWS anomalies at upper level are mainly confined to the Mediterranean region and the associated wave activity is weaker compared with that in 1928–1948/1975–1995. Since the AO–SAT relationship has experienced two significant periods and two insignificant periods, it suggests a weakening of the AO–SAT relationship in recent two decades.
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impact of Arctic Oscillation on the east asian climate a review
Earth-Science Reviews, 2017Co-Authors: Huijun Wang, Yongqi GaoAbstract:Abstract The Arctic Oscillation (AO), which depicts a most dominant large-scale seesaw between the mid-latitudes and Arctic atmospheric mass, influences climate over Eurasia, North America, eastern Canada, North Africa, and the Middle East, especially during boreal winter. This review, with a special focus on the East Asian region, summarizes the climatic impact of AO. It begins with a description of the spatial structure of AO and the related climatic anomalies. The relationship of winter AO with the simultaneous East Asian winter climate (e.g. the East Asian winter monsoon (EAWM), cold surges/cold waves, and precipitation) and its instability are then followed. It is generally accepted that, through impacting the Siberian high, westerly wind, blocking frequency, Rossby wave activities etc., a positive phase of winter AO is associated with a weaker-than-normal EAWM, warmer conditions in East Asia, less frequency of cold surges/cold waves, increasing (decreasing) of winter precipitation in south (north) parts of East Asia; and vice versa. Notably, the pathways that the winter AO exerts impact are different. Besides, the AO-EAWM and the AO-cold surges/cold wave linkages have spatial and temporal variations. Subsequently, an overview of the inter-seasonal linkages between the East Asian summer monsoon with the preceding spring/winter AO is presented. There is a generally accepted knowledge that a positive spring AO is followed by significant positive summer precipitation anomalies in southern China and western Pacific as well as negative ones in the lower valley of Yangtze River and southern Japan. Finally, this review synthesizes the impact of winter/spring AO on the East Asian spring climate (e.g. dust storm, temperature, and precipitation) and discusses the potential predictive value of AO. The projection of AO and its impact on the East Asian climate in future has been barely explored. We conclude that, along with the long-term observation data, the linkage between AO and the East Asian climate on the sub-seasonal and decadal time scales, how tropical and extratropical forcing modulates the linkage and how the linkage evolves under future warming conditions should be more investigated. Notably, the change of AO during 1990–2013 winters could explain the Eurasian cooling but failed to explain the Arctic warming. In the future, the effect of Ural blocking on Arctic and Eurasian climate and their connection might be a hot topic.
Yongqi Gao - One of the best experts on this subject based on the ideXlab platform.
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recent intensified impact of december Arctic Oscillation on subsequent january temperature in eurasia and north africa
Climate Dynamics, 2019Co-Authors: Huijun Wang, Yongqi GaoAbstract:This study reveals an intensified influence of December Arctic Oscillation (AO) on the subsequent January surface air temperature (SAT) over Eurasia and North Africa in recent decades. The connection is statistically insignificant during 1957/58–1979/80 (P1), which becomes statistically significant during 1989/90–2011/12 (P2). The possible causes are further investigated. Associated with positive December AO during P2, significant anomalous anticyclone emerges over the central North Atlantic, which is accompanied with significant westerly and easterly anomalies along 45°−65°N and 20°−40°N, respectively. This favors the significant influence of December AO on the subsequent January SAT and atmospheric circulation over Eurasia and North Africa via triggering the North Atlantic tripole sea surface temperature (SST) anomaly that persists into the subsequent January. By contrast, the December AO-related anomalous anticyclone during P1 is weak and is characterized by two separate centers located in the eastern and western North Atlantic. Correspondingly, the westerly and easterly anomalies over the North Atlantic Ocean are weak and the-related tripole SST anomaly is not well formed, unfavorable for the persistent impact of the December AO into the subsequent January. Further analyses indicate that the different anomalous anticyclone associated with the December AO over the North Atlantic may be induced by the strengthened synoptic-scale eddy feedbacks over the North Atlantic, which may be related to the interdecadal intensification of the storm track activity. Additionally, the planetary stationary wave related to the December AO propagates from surface into upper stratosphere at mid-latitudes during P2, which further propagates downward to the troposphere and causes anomalous atmospheric circulation in the subsequent January.
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impact of Arctic Oscillation on the east asian climate a review
Earth-Science Reviews, 2017Co-Authors: Huijun Wang, Yongqi GaoAbstract:Abstract The Arctic Oscillation (AO), which depicts a most dominant large-scale seesaw between the mid-latitudes and Arctic atmospheric mass, influences climate over Eurasia, North America, eastern Canada, North Africa, and the Middle East, especially during boreal winter. This review, with a special focus on the East Asian region, summarizes the climatic impact of AO. It begins with a description of the spatial structure of AO and the related climatic anomalies. The relationship of winter AO with the simultaneous East Asian winter climate (e.g. the East Asian winter monsoon (EAWM), cold surges/cold waves, and precipitation) and its instability are then followed. It is generally accepted that, through impacting the Siberian high, westerly wind, blocking frequency, Rossby wave activities etc., a positive phase of winter AO is associated with a weaker-than-normal EAWM, warmer conditions in East Asia, less frequency of cold surges/cold waves, increasing (decreasing) of winter precipitation in south (north) parts of East Asia; and vice versa. Notably, the pathways that the winter AO exerts impact are different. Besides, the AO-EAWM and the AO-cold surges/cold wave linkages have spatial and temporal variations. Subsequently, an overview of the inter-seasonal linkages between the East Asian summer monsoon with the preceding spring/winter AO is presented. There is a generally accepted knowledge that a positive spring AO is followed by significant positive summer precipitation anomalies in southern China and western Pacific as well as negative ones in the lower valley of Yangtze River and southern Japan. Finally, this review synthesizes the impact of winter/spring AO on the East Asian spring climate (e.g. dust storm, temperature, and precipitation) and discusses the potential predictive value of AO. The projection of AO and its impact on the East Asian climate in future has been barely explored. We conclude that, along with the long-term observation data, the linkage between AO and the East Asian climate on the sub-seasonal and decadal time scales, how tropical and extratropical forcing modulates the linkage and how the linkage evolves under future warming conditions should be more investigated. Notably, the change of AO during 1990–2013 winters could explain the Eurasian cooling but failed to explain the Arctic warming. In the future, the effect of Ural blocking on Arctic and Eurasian climate and their connection might be a hot topic.
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on the strengthened relationship between the east asian winter monsoon and Arctic Oscillation a comparison of 1950 70 and 1983 2012
Journal of Climate, 2014Co-Authors: Huijun Wang, Yongqi GaoAbstract:AbstractIn this paper, the authors use NCEP reanalysis and 40-yr ECMWF Re-Analysis (ERA-40) data to document the strengthened relationship between the East Asian winter monsoon (EAWM) and winter Arctic Oscillation (AO) on the interannual time scale with a comparison of 1950–70 and 1983–2012. Their connection was statistically insignificant during 1950–70, whereas it was statistically significant during 1983–2012. The latter significant connection might be attributed to the East Asian jet stream (EAJS) upstream extension: the EAJS signal is relatively confined to the western North Pacific before the 1970s, whereas it extends westward toward East Asia after the 1980s. This upstream extension leads to the rearrangement of eastward-propagating Rossby waves with a much wider horizontal structure, thereby bonding the EAWM and the AO.Furthermore, the authors present observational evidence and model simulations demonstrating that the reduction of autumn Arctic sea ice cover (ASIC) is responsible for the strengthe...
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spring Arctic Oscillation east asian summer monsoon connection through circulation changes over the western north pacific
Climate Dynamics, 2011Co-Authors: Daoyi Gong, Seongjoong Kim, Yongqi Gao, Jing Yang, Dong Guo, Tianjun ZhouAbstract:In the present study the links between spring Arctic Oscillation (AO) and East Asian summer monsoon (EASM) was investigated with focus on the importance of the North Pacific atmospheric circulation and sea surface temperature (SST). To reduce the statistical uncertainty, we analyzed high-pass filtered data with the inter-annual time scales, and excluded the El Nino/Southern Oscillation signals in the climate fields using a linear fitting method. The significant relationship between spring AO and EASM are supported by the changes of multi-monsoon components, including monsoon indices, precipitation, and three-dimensional atmospheric circulations. Following a stronger positive spring AO, an anomalous cyclonic circulation at 850 hPa appears in southeastern Asia and the western North Pacific in summer, with the easterly anomalies spanning from the Pacific to Asian continent along 25°N–30°N and the westerly anomalies south of 15°N. At the same time, the summer western North Pacific subtropical high becomes weaker. Consistently, the positive precipitation anomalies are developed over a broad region south of 30°N stretching from southern China to the western Pacific and the negative precipitation anomalies appear in the lower valley of the Yangtze River and southern Japan. The anomalous cyclone in the western North Pacific persisting from spring to summer plays a key role in modulating EASM and monsoon precipitation by a positive air-sea feedback mechanism. During spring the AO-associated atmospheric circulation change produces warmer SSTs between 150°E–180° near the equator. The anomalous sensible and latent heating, in turn, intensifies the cyclone through a Gill-type response of the atmosphere. Through this positive feedback, the tropical atmosphere and SST patterns sustain their strength from spring to summer, that consequently modifies the monsoon trough and the western North Pacific subtropical high and eventually the EASM precipitation. Moreover, the SST response to AO-circulation is supported by the numerical simulations of an ocean model, and the anomalous atmospheric circulation over the western North Pacific is also reproduced by the dedicated numerical simulations using the coupled atmosphere–ocean model. The observation evidence and numerical simulations suggest the spring AO can impact the EASM via triggering tropical air-sea feedback over the western North Pacific.
Daoyi Gong - One of the best experts on this subject based on the ideXlab platform.
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spring Arctic Oscillation east asian summer monsoon connection through circulation changes over the western north pacific
Climate Dynamics, 2011Co-Authors: Daoyi Gong, Seongjoong Kim, Yongqi Gao, Jing Yang, Dong Guo, Tianjun ZhouAbstract:In the present study the links between spring Arctic Oscillation (AO) and East Asian summer monsoon (EASM) was investigated with focus on the importance of the North Pacific atmospheric circulation and sea surface temperature (SST). To reduce the statistical uncertainty, we analyzed high-pass filtered data with the inter-annual time scales, and excluded the El Nino/Southern Oscillation signals in the climate fields using a linear fitting method. The significant relationship between spring AO and EASM are supported by the changes of multi-monsoon components, including monsoon indices, precipitation, and three-dimensional atmospheric circulations. Following a stronger positive spring AO, an anomalous cyclonic circulation at 850 hPa appears in southeastern Asia and the western North Pacific in summer, with the easterly anomalies spanning from the Pacific to Asian continent along 25°N–30°N and the westerly anomalies south of 15°N. At the same time, the summer western North Pacific subtropical high becomes weaker. Consistently, the positive precipitation anomalies are developed over a broad region south of 30°N stretching from southern China to the western Pacific and the negative precipitation anomalies appear in the lower valley of the Yangtze River and southern Japan. The anomalous cyclone in the western North Pacific persisting from spring to summer plays a key role in modulating EASM and monsoon precipitation by a positive air-sea feedback mechanism. During spring the AO-associated atmospheric circulation change produces warmer SSTs between 150°E–180° near the equator. The anomalous sensible and latent heating, in turn, intensifies the cyclone through a Gill-type response of the atmosphere. Through this positive feedback, the tropical atmosphere and SST patterns sustain their strength from spring to summer, that consequently modifies the monsoon trough and the western North Pacific subtropical high and eventually the EASM precipitation. Moreover, the SST response to AO-circulation is supported by the numerical simulations of an ocean model, and the anomalous atmospheric circulation over the western North Pacific is also reproduced by the dedicated numerical simulations using the coupled atmosphere–ocean model. The observation evidence and numerical simulations suggest the spring AO can impact the EASM via triggering tropical air-sea feedback over the western North Pacific.
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influence of Arctic Oscillation on dust activity over northeast asia
Atmospheric Environment, 2011Co-Authors: Rui Mao, Daoyi Gong, Yaping Shao, Jhoon KimAbstract:Abstract The northeast Asian dust process during the spring seasons in the years 1982–2006 was simulated by the Integrated Wind Erosion Modeling System (IWEMS). The influence of Arctic Oscillation (AO) on dust activities was investigated by analyzing surface observations and model simulations. There is a significant relationship between AO and dust activity; a positive AO phase is associated with decreased (increased) dust storm frequency in Mongolia (Taklimakan Desert) and enhanced anticyclonic (southeastward) dust transport over northwestern China (North China). The AO-dust relation is mainly due to changes in the westerly jet and geopotential height in the middle troposphere; a positive AO phase induces a northward shift of the polar jet, an intensified westerly jet over northern Tibetan Plateau, and a positive geopotential height anomaly over Mongolia. The northern shift of the polar jet reduces the frequency of intense cyclones in Mongolia, thereby causing a decrease in the dust storm frequency. The intensified westerly jet stream over the northern Tibetan Plateau increases the dust storm frequency in the Taklimakan Desert. The positive geopotential height anomaly over Mongolia initiates an anticyclonic dust transport anomaly in the middle troposphere over northwestern China. It also induces a southeastward dust transport anomaly over North China. The reverse situations are true for a negative AO phase.
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Arctic Oscillation signals in the east asian summer monsoon
Journal of Geophysical Research, 2003Co-Authors: Daoyi GongAbstract:[1] The present study examines the relationship between the Arctic Oscillation (AO) and the East Asian summer monsoon. Two rainfall data sets are used. One is obtained from 10 stations along the Yangtze River to the southern Japan and the other from gridded global land rainfall data for the period 1900–1998. All data are high-pass filtered before analyzing to highlight the interannual variability. Results show that the AO significantly influences on year-to-year variations in the East Asian summer monsoon rainfall. When AO leads by one month, the correlation between May–July AO and summer total rainfall is −0.44. When AO leads by two months, correlation becomes −0.32. Of all monthly, May AO shows the strongest connection to the summer monsoon rainfall. Correlation coefficient between them is −0.45. The large-scale atmospheric circulation patterns in East Asia in association with the AO are also evident. A positive phase of the AO in late spring is found to lead to a northward shift in the summertime upper tropospheric jet stream over East Asia. This northward shift of the jet stream is closely related to anomalous sinking motion in 20°–40°N and rising motion in surrounding regions. These changes give rise to a drier condition over the region extending from the Yangtze River valley to the southern Japan and a wetter condition in the southern China. Possible mechanisms connecting the late spring AO and summer monsoon rainfall are suggested.
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east asian winter monsoon and Arctic Oscillation
Geophysical Research Letters, 2001Co-Authors: Daoyi Gong, Shaowu Wang, Jinhong ZhuAbstract:In this study, the connection between Arctic Oscillation (AO) and variability of East Asian winter monsoon is investigated. Two indices are chosen to describe the winter monsoon. One is the intensity of the Siberian High, defined as the average SLP over the center region, and the other is the temperature of eastern China, averaged over 76 surface stations. These are two tightly related components, correlate at −0.62 for period 1951–99. Temperature drops by 0.64 degrees Celsius in association with a one standard deviation increase in Siberian High intensity. It is found that there are significant out-of-phase relationships between the AO and the East Asian winter monsoon. The correlation coefficient between the AO and the Siberian High intensity index is −0.48 for period 1958–98. AO is also significantly correlated with the temperature of eastern China at 0.34. However, when the linear trend is removed, the correlation between AO and temperature is no longer significant. But the strong connection between the AO and Siberian High, and between the Siberian High and temperature are still significant. These results reveal that the AO influences the East Asian winter monsoon through the impact on the Siberian High. Negative phase of the AO is concurrent with a stronger East Asian Trough and an anomalous anticyclonic flow over Urals at the middle troposphere (500hPa). Both the AO and the Eurasian pattern play important roles in changes of the Siberian High and/or East Asian winter monsoon. They account for 13.0% and 36.0% of the variance in the Siberian High respectively.