The Eurasian teleconnection pattern （EU） is an important low-frequency pattern with well-known impacts on climate anomalies in Eurasia. The difference of low-level v-winds in several regions in the Eurasian mid-high...The Eurasian teleconnection pattern （EU） is an important low-frequency pattern with well-known impacts on climate anomalies in Eurasia. The difference of low-level v-winds in several regions in the Eurasian mid-high latitudes is defined as the EU index （EUIv）. In this study, the relationship between the winter EUIv and precipitation in the following summer over China is investigated. Results show that there is a significant positive （negative） correlation between the winter EUIv and the following summer precipitation over North China （the Yangtze River-Huaihe River basins）. Meanwhile, an interdecadal variability exists in the interannual relationship, and the correlation has become significantly enhanced since the early 1980s. Thus, the proposed EUIv may have implications for the prediction of summer precipitation anomalies over China. In positive winter EUIv years, three cyclonic circulation anomalies are observed--over the Ural Mountains, the Okhotsk Sea, and the subtropical western North Pacific. That is, the Ural blocking and Okhotsk blocking are inactive, zonal circulation prevails in the mid-high latitudes, and the western Pacific subtropical high tends to be weaker and locates to the north of its normal position in the following summer. This leads to above-normal moisture penetrating into the northern part of East China, and significant positive （negative） precipitation anomalies over North China （the Yangtze River-Huaihe River basins）, and vice versa. Further examination shows that the SST anomalies over the Northwest Pacific and subtropical central North Pacific may both contribute to the formation of EUIv-related circulation anomalies over the western North Pacific.展开更多
Phase synchronization clustering method is used to detect the process of extreme weather events rather than extreme values events mathematically. The applicability is discussed from the aspects of noise intensity and ...Phase synchronization clustering method is used to detect the process of extreme weather events rather than extreme values events mathematically. The applicability is discussed from the aspects of noise intensity and sequence length and the observed data are applied practically. The detection process shows that clustering measure difference can detect the temporal process objectively to a certain degree and it has certain application to detect the temporal process of extreme weather events.展开更多
In view of extreme values events mathematically rather than the process about extreme weather events, phase synchronization clustering method is introduced and the applicability of the method is discussed from the asp...In view of extreme values events mathematically rather than the process about extreme weather events, phase synchronization clustering method is introduced and the applicability of the method is discussed from the aspects of noise intensity and sequence length. At last the observed data is applied. The results show that clustering measure difference can detect the temporal process objectively to a certain degree and it has certain application to detect the temporal proc- ess of extreme weather events.展开更多
Sea surface temperature anomaly(SSTA)is a major signal for prediction of summer precipitation in East Asia.The relationship between SSTA in the tropical oceans and summer precipitation in East Asia has been documented...Sea surface temperature anomaly(SSTA)is a major signal for prediction of summer precipitation in East Asia.The relationship between SSTA in the tropical oceans and summer precipitation in East Asia has been documented in many studies.However,the relationship between SSTA and late summer(July–August)precipitation(JAP)over Northeast China(NEC)on the interannual timescale has received little attention.In this study,we examine the relationship between Indian Ocean Basin warming(IOBW)anomalies in spring and the JAP in NEC since the early1960 s.A significant positive correlation is found between the spring IOBW index and JAP over NEC.The positive spring IOBW anomaly is followed by an anomalous anticyclone from Northwest Pacific to the Korean Peninsula.This anomalous anticyclone favors a significantly strong and northward western Pacific subtropical high(WPSH),which facilitates anomalous southerly winds over NEC and the transport of more water vapor into this region.Further analysis indicates that the spring IOBW anomalies have important impacts on the vertical air motion in the tropics and subtropics during the summer.Significant anomalous upward(downward)motion covering Indonesia(Northwest Pacific to the southern Korean Peninsula)occurs when the IOBW is in its positive phase,which favors the northward movement of the WPSH in late summer and more precipitation over NEC in July–August.Modulation of the atmospheric circulation by this mechanism further influences the JAP over NEC.展开更多
In this study, an interdecadal shift of summer precipitation over northern East Asia （NEA） was identified, demon-strating that summer precipitation decreased abruptly after 1998/99. The synchronous shift in summer m...In this study, an interdecadal shift of summer precipitation over northern East Asia （NEA） was identified, demon-strating that summer precipitation decreased abruptly after 1998/99. The synchronous shift in summer moisture budget and water vapor transport over NEA was further investigated by using the NCEP/NCAR reanalysis data. The results indicate that water vapor transported northward into NEA from three low-latitude paths was limited because most water vapor was transported eastward. Water vapor transported from the westerly path in mid-high （WMH） lat-itudes exhibited significant correlations with summer precipitation in NEA and experienced a significant adjustment in the late 1990s. Regarding the spatial distributions of water vapor transport, less input was found through the west-ern boundary while more output occurred through the eastern boundary of NEA, and zonal water vapor transport fluxes mainly concentrated at the low to middle levels, which led to the summer precipitation shift in NEA around the late 1990s. Furthermore, it is also confirmed that the wind anomalies （rather than the moisture disturbance） as the dominant internal dynamic factor and Pacific Decadal Oscillation/Atlantic Multidecadal Oscillation （PDO/AMO） as possible external force played important roles in influencing the water vapor transport and causing the summer pre-cipitation shift over NEA in the late 1990s.展开更多
The East Asia-Pacific(EAP)and Eurasian(EU)teleconnections are independent of each other on the seasonal timescale(with a correlation coefficient of only 0.03).But they may occur concurrently with consistent or opposit...The East Asia-Pacific(EAP)and Eurasian(EU)teleconnections are independent of each other on the seasonal timescale(with a correlation coefficient of only 0.03).But they may occur concurrently with consistent or opposite phases.This paper investigates their synergistic effect on the summer precipitation in North Asia.Based on the signs/phases of EAP and EU indices,the EAP and EU teleconnection anomalies occur in four cases:(Ⅰ)positive EAP+positive EU,(Ⅱ)negative EAP+negative EU,(Ⅲ)positive EAP+negative EU,and(Ⅳ)negative EAP+positive EU.Further analyses show that these four configurations of EAP and EU anomalies are coherently related to different atmospheric circulations over the midlatitude Eurasian continent,leading to different summer precipitation modes in North Asia.CategoryⅠ(Ⅱ)corresponds to a zonal tripole structure of the geopotential height at 500 hPa over eastern Europe and the Sea of Japan,leading to less(more)than normal precipitation in eastern Europe,Japan,and the surrounding areas,and more(less)precipitation from central China to Lake Baikal and eastern Russia.CategoryⅢ(Ⅳ)corresponds to a meridional dipole structure of the geopotential height at 500 hPa over North Asia,leading to more(less)precipitation in the northern North Asia and less(more)precipitation in most of the southern North Asia.Independent analysis reveals that the EAP teleconnection itself is positively correlated with the precipitation in the region between the eastern part of Lake Baikal and Okhotsk Sea,and negatively correlated with the precipitation in the region between Northeast China and Japan.Coincidently,the EU pattern and precipitation have negative correlations in Ural Mountain and Okhotsk Sea areas and positive correlations in the Lake Baikal area.The respective relations of EAP and EU with the summer precipitation in North Asia suggest that the EAP northern lobe overlapped with the EU central and eastern lobes could extend the geopotential anomalies over Lake Baikal to Russian Far East,creating an EAP-EU synergistic effect on the summer precipitation in North Asia.展开更多
Based on the NCEP/NCAR reanalysis data and Chinese observational data during 1961–2013, atmospheric circulation patterns over East Asia in summer and their connection with precipitation and surface air temperature in...Based on the NCEP/NCAR reanalysis data and Chinese observational data during 1961–2013, atmospheric circulation patterns over East Asia in summer and their connection with precipitation and surface air temperature in eastern China as well as associated external forcing are investigated. Three patterns of the atmospheric circulation are identified, all with quasi-barotropic structures：（1） the East Asia/Pacific（EAP） pattern,（2） the Baikal Lake/Okhotsk Sea（BLOS） pattern, and（3） the eastern China/northern Okhotsk Sea（ECNOS） pattern. The positive EAP pattern significantly increases precipitation over the Yangtze River valley and favors cooling north of the Yangtze River and warming south of the Yangtze River in summer. The warm sea surface temperature anomalies over the tropical Indian Ocean suppress convection over the northwestern subtropical Pacific through the Ekman divergence induced by a Kelvin wave and excite the EAP pattern. The positive BLOS pattern is associated with below-average precipitation south of the Yangtze River and robust cooling over northeastern China. This pattern is triggered by anomalous spring sea ice concentration in the northern Barents Sea. The anomalous sea ice concentration contributes to a Rossby wave activity flux originating from the Greenland Sea, which propagates eastward to North Pacific. The positive ECNOS pattern leads to below-average precipitation and significant warming over northeastern China in summer. The reduced soil moisture associated with the earlier spring snowmelt enhances surface warming over Mongolia and northeastern China and the later spring snowmelt leads to surface cooling over Far East in summer, both of which are responsible for the formation of the ECNOS pattern.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.41505061,41530531 and 41405092)the National Basic Research Program of China(Grant Nos.2012CB955902 and 2013CB430204)
文摘The Eurasian teleconnection pattern （EU） is an important low-frequency pattern with well-known impacts on climate anomalies in Eurasia. The difference of low-level v-winds in several regions in the Eurasian mid-high latitudes is defined as the EU index （EUIv）. In this study, the relationship between the winter EUIv and precipitation in the following summer over China is investigated. Results show that there is a significant positive （negative） correlation between the winter EUIv and the following summer precipitation over North China （the Yangtze River-Huaihe River basins）. Meanwhile, an interdecadal variability exists in the interannual relationship, and the correlation has become significantly enhanced since the early 1980s. Thus, the proposed EUIv may have implications for the prediction of summer precipitation anomalies over China. In positive winter EUIv years, three cyclonic circulation anomalies are observed--over the Ural Mountains, the Okhotsk Sea, and the subtropical western North Pacific. That is, the Ural blocking and Okhotsk blocking are inactive, zonal circulation prevails in the mid-high latitudes, and the western Pacific subtropical high tends to be weaker and locates to the north of its normal position in the following summer. This leads to above-normal moisture penetrating into the northern part of East China, and significant positive （negative） precipitation anomalies over North China （the Yangtze River-Huaihe River basins）, and vice versa. Further examination shows that the SST anomalies over the Northwest Pacific and subtropical central North Pacific may both contribute to the formation of EUIv-related circulation anomalies over the western North Pacific.
文摘Phase synchronization clustering method is used to detect the process of extreme weather events rather than extreme values events mathematically. The applicability is discussed from the aspects of noise intensity and sequence length and the observed data are applied practically. The detection process shows that clustering measure difference can detect the temporal process objectively to a certain degree and it has certain application to detect the temporal process of extreme weather events.
文摘In view of extreme values events mathematically rather than the process about extreme weather events, phase synchronization clustering method is introduced and the applicability of the method is discussed from the aspects of noise intensity and sequence length. At last the observed data is applied. The results show that clustering measure difference can detect the temporal process objectively to a certain degree and it has certain application to detect the temporal proc- ess of extreme weather events.
基金Supported by the National Key Research and Development Program of China(2018YFA0606301)National Natural Science Foundation of China(41875093,41705074,and 41530531).
文摘Sea surface temperature anomaly(SSTA)is a major signal for prediction of summer precipitation in East Asia.The relationship between SSTA in the tropical oceans and summer precipitation in East Asia has been documented in many studies.However,the relationship between SSTA and late summer(July–August)precipitation(JAP)over Northeast China(NEC)on the interannual timescale has received little attention.In this study,we examine the relationship between Indian Ocean Basin warming(IOBW)anomalies in spring and the JAP in NEC since the early1960 s.A significant positive correlation is found between the spring IOBW index and JAP over NEC.The positive spring IOBW anomaly is followed by an anomalous anticyclone from Northwest Pacific to the Korean Peninsula.This anomalous anticyclone favors a significantly strong and northward western Pacific subtropical high(WPSH),which facilitates anomalous southerly winds over NEC and the transport of more water vapor into this region.Further analysis indicates that the spring IOBW anomalies have important impacts on the vertical air motion in the tropics and subtropics during the summer.Significant anomalous upward(downward)motion covering Indonesia(Northwest Pacific to the southern Korean Peninsula)occurs when the IOBW is in its positive phase,which favors the northward movement of the WPSH in late summer and more precipitation over NEC in July–August.Modulation of the atmospheric circulation by this mechanism further influences the JAP over NEC.
基金Supported by the National Natural Science Foundation of China(41575082,41530531,and 41475064)National Key Research and Development Program of China(2017YFC1502303)
文摘In this study, an interdecadal shift of summer precipitation over northern East Asia （NEA） was identified, demon-strating that summer precipitation decreased abruptly after 1998/99. The synchronous shift in summer moisture budget and water vapor transport over NEA was further investigated by using the NCEP/NCAR reanalysis data. The results indicate that water vapor transported northward into NEA from three low-latitude paths was limited because most water vapor was transported eastward. Water vapor transported from the westerly path in mid-high （WMH） lat-itudes exhibited significant correlations with summer precipitation in NEA and experienced a significant adjustment in the late 1990s. Regarding the spatial distributions of water vapor transport, less input was found through the west-ern boundary while more output occurred through the eastern boundary of NEA, and zonal water vapor transport fluxes mainly concentrated at the low to middle levels, which led to the summer precipitation shift in NEA around the late 1990s. Furthermore, it is also confirmed that the wind anomalies （rather than the moisture disturbance） as the dominant internal dynamic factor and Pacific Decadal Oscillation/Atlantic Multidecadal Oscillation （PDO/AMO） as possible external force played important roles in influencing the water vapor transport and causing the summer pre-cipitation shift over NEA in the late 1990s.
基金Supported by the National Key Research and Development Program of China(2018YFA0606301 and 2018YFC1507702)National Natural Science Foundation of China(41875100,41575082,and 41530531).
文摘The East Asia-Pacific(EAP)and Eurasian(EU)teleconnections are independent of each other on the seasonal timescale(with a correlation coefficient of only 0.03).But they may occur concurrently with consistent or opposite phases.This paper investigates their synergistic effect on the summer precipitation in North Asia.Based on the signs/phases of EAP and EU indices,the EAP and EU teleconnection anomalies occur in four cases:(Ⅰ)positive EAP+positive EU,(Ⅱ)negative EAP+negative EU,(Ⅲ)positive EAP+negative EU,and(Ⅳ)negative EAP+positive EU.Further analyses show that these four configurations of EAP and EU anomalies are coherently related to different atmospheric circulations over the midlatitude Eurasian continent,leading to different summer precipitation modes in North Asia.CategoryⅠ(Ⅱ)corresponds to a zonal tripole structure of the geopotential height at 500 hPa over eastern Europe and the Sea of Japan,leading to less(more)than normal precipitation in eastern Europe,Japan,and the surrounding areas,and more(less)precipitation from central China to Lake Baikal and eastern Russia.CategoryⅢ(Ⅳ)corresponds to a meridional dipole structure of the geopotential height at 500 hPa over North Asia,leading to more(less)precipitation in the northern North Asia and less(more)precipitation in most of the southern North Asia.Independent analysis reveals that the EAP teleconnection itself is positively correlated with the precipitation in the region between the eastern part of Lake Baikal and Okhotsk Sea,and negatively correlated with the precipitation in the region between Northeast China and Japan.Coincidently,the EU pattern and precipitation have negative correlations in Ural Mountain and Okhotsk Sea areas and positive correlations in the Lake Baikal area.The respective relations of EAP and EU with the summer precipitation in North Asia suggest that the EAP northern lobe overlapped with the EU central and eastern lobes could extend the geopotential anomalies over Lake Baikal to Russian Far East,creating an EAP-EU synergistic effect on the summer precipitation in North Asia.
基金Supported by the National Natural Science Foundation of China(41530531,41675092,and 41305056)China Meteorological Administration Special Public Welfare Research Fund(GYHY201506001)
文摘Based on the NCEP/NCAR reanalysis data and Chinese observational data during 1961–2013, atmospheric circulation patterns over East Asia in summer and their connection with precipitation and surface air temperature in eastern China as well as associated external forcing are investigated. Three patterns of the atmospheric circulation are identified, all with quasi-barotropic structures：（1） the East Asia/Pacific（EAP） pattern,（2） the Baikal Lake/Okhotsk Sea（BLOS） pattern, and（3） the eastern China/northern Okhotsk Sea（ECNOS） pattern. The positive EAP pattern significantly increases precipitation over the Yangtze River valley and favors cooling north of the Yangtze River and warming south of the Yangtze River in summer. The warm sea surface temperature anomalies over the tropical Indian Ocean suppress convection over the northwestern subtropical Pacific through the Ekman divergence induced by a Kelvin wave and excite the EAP pattern. The positive BLOS pattern is associated with below-average precipitation south of the Yangtze River and robust cooling over northeastern China. This pattern is triggered by anomalous spring sea ice concentration in the northern Barents Sea. The anomalous sea ice concentration contributes to a Rossby wave activity flux originating from the Greenland Sea, which propagates eastward to North Pacific. The positive ECNOS pattern leads to below-average precipitation and significant warming over northeastern China in summer. The reduced soil moisture associated with the earlier spring snowmelt enhances surface warming over Mongolia and northeastern China and the later spring snowmelt leads to surface cooling over Far East in summer, both of which are responsible for the formation of the ECNOS pattern.
