The western North Pacific summer monsoon(WNPSM)is an important subcomponent of the Asian summer monsoon.The equatorial zonal wind(EZW)in the lower troposphere over the western Pacific may play a critical role in the e...The western North Pacific summer monsoon(WNPSM)is an important subcomponent of the Asian summer monsoon.The equatorial zonal wind(EZW)in the lower troposphere over the western Pacific may play a critical role in the evolution of the El Niño-Southern Oscillation(ENSO).The possible linkage between the EZW over the western Pacific and the offequatorial monsoonal winds associated with the WNPSM and its decadal changes have not yet been fully understood.Here,we find a non-stationary relationship between the WNPSM and the western Pacific EZW,significantly strengthening their correlation around the late 1980s/early 1990s.This observed shift in the WNPSM–EZW relationship could be explained by the changes in the related sea surface temperature(SST)configurations across the tropical oceans.The enhanced influence from the springtime tropical North Atlantic,summertime tropical central Pacific,and maritime continent SST anomalies may be working together in contributing to the recent intensified WNPSM–EZW co-variability.The observed recent strengthening of the WNPSM–EZW relationship may profoundly impact the climate system,including prompting more effective feedback from the WNPSM on subsequent ENSO evolution and bolstering a stronger biennial tendency of the WNPSM–ENSO coupled system.The results obtained herein imply that the WNPSM,EZW,ENSO,and the tropical North Atlantic SST may be closely linked within a unified climate system with a quasi-biennial rhythm occurring during recent decades,accompanied by a reinforcement of the WNPSM–ENSO interplay quite possibly triggered by enhanced tropical Pacific–Atlantic cross-basin interactions.These results highlight the importance of the tropical Atlantic cross-basin influences in shaping the spatial structure of WNPSM-related wind anomalies and the WNPSM–ENSO interaction.展开更多
This study reveals that the interannual variability of the western edge of the western North Pacific(WNP)subtropical high(WNPSH)in early summer experienced an interdecadal decrease around 1990.Correspondingly,the zona...This study reveals that the interannual variability of the western edge of the western North Pacific(WNP)subtropical high(WNPSH)in early summer experienced an interdecadal decrease around 1990.Correspondingly,the zonal movement of the WNPSH and the zonal extension of the high-pressure anomaly over the WNP(WNPHA)in abnormal years possess smaller ranges after 1990.The different influences of the tropical SSTAs are important for this interdecadal change,which exhibit slow El Nino decaying pattern before 1990 while rapid transformation from El Nino to La Nina after 1990.The early summer tropical SSTAs and the relevant atmospheric circulation anomalies present obvious interdecadal differences.Before 1990,the warm SSTAs over the northern Indian Ocean and southern South China Sea favor the WNPHA through eastward-propagating Kelvin wave and meridional-vertical circulation,respectively.Meanwhile,the warm SSTA over the tropical central Pacific induces anomalous ascent to its northwest through the Gill response,which could strengthen the anomalous descent over the WNP through meridional-vertical circulation and further favor the eastward extension of the WNPHA to central Pacific.After 1990,the warm SSTAs over the Maritime Continent and northern Indian Ocean cause the WNPHA through meridional-vertical and zonal-vertical circulation,respectively.Overall,the anomalous warm SSTs and ascent and the resultant anomalous descent over the WNP are located more westward and southward after 1990 than before 1990.Consequently,the WNPHA features narrower zonal range and less eastward extension after 1990,corresponding to the interdecadal decease in the interannual variability of the western edge of the WNPSH.On the other hand,the dominant oscillation period of ENSO experienced an interdecadal reduction around 1990,contributing to the change of the El Nino SSTA associated with the anomalous WNPSH from slow decaying type to rapid transformation type.展开更多
The observed tropospheric biennial oscillation (TBO) in the western North Pacific (WNP) monsoon region has an interdecadal variability with a period of 40-50 yr. That suggests a weaker effect of the TBO on the Eas...The observed tropospheric biennial oscillation (TBO) in the western North Pacific (WNP) monsoon region has an interdecadal variability with a period of 40-50 yr. That suggests a weaker effect of the TBO on the East Asia followed by a stronger one. A simple analytic model was designed to investigate the mechanism of the interdecadal variability of the TBO. The results indicated that a local TBO air-sea system not only supports the TBO variability in the WNP monsoon region but also produces an interdecadal variability of the TBO.展开更多
The simulation of a higher-resolution oceanic GCM forced with COADS surface conditions during 1945 ~ 1993 was analyzed with insight into how the North Pacific responds to the surface forcing. The decadal-to-interdeca...The simulation of a higher-resolution oceanic GCM forced with COADS surface conditions during 1945 ~ 1993 was analyzed with insight into how the North Pacific responds to the surface forcing. The decadal-to-interdecadal variabilities in the thermal and dynamical fields especially those associated with the 1976/1977 regime shift in the North Pacific were investigated. The model successfully captures the dominant SST anomaly mode on the decadal-to-interdecadal time scales as well as the major feature of SST anomalies in the 1976/1977 regime shift. The model also successfully reproduces two typical subduction events that link the tropical and extratropical oceanic temperature anomalies during the 1970s and the 1980s. Most importantly, the model simulates the dynamical adjustment of the upper ocean under the surface wind forcing. The typical surface circulation anomaly is characterized by a pattern that is simultaneously related to the wind stress anomalies. The typical anomalous pattern for the entire upper-ocean is characterized by coherent anomalies of two oceanic gyres, i.e. , the subtropical and subpolar gyres. The delayed response and slower adjustment of the gyres, especially of the subpolar gyre, give rise to a persistent SST anomaly in the central North Pacific. The upper-ocean heat budgets in three target regions, i.e. , the central North Pacific, the Californian coastal region and the KOE region, are examined. The cooling in the central North Pacific around 1976/1977 is attributed to the heat flux and mefidional advection anomalies. The associated warming in the Californian coastal region is only due to the heat flux anomaly. A cooling shift in the KOE region which lags that in the central basin by 3 to 4 a is largely due to the meridional advection anomaly and the heat flux acts only as a damping role.展开更多
The western North Pacific subtropical high (WNPSH) is an important circulation system that impacts the East Asian summer climate. The interannual variability of the WNPSH is modulated by tropical air-sea interaction...The western North Pacific subtropical high (WNPSH) is an important circulation system that impacts the East Asian summer climate. The interannual variability of the WNPSH is modulated by tropical air-sea interaction. In order to make it clear which oceanic regions are crucial to the interannual variability of the WNPSH, the research progresses in this regard in the past decade are reviewed. Based on the review, it is recognized that five oceanic regions are responsible for the interannual variability of the WNPSH in summer, including the equatorial central-eastern Pacific Ocean, tropical Indian Ocean, subtropical western North Pacific, the vicinity of the maritime continent, and the tropical Atlantic Ocean. The mechanisms how the sea surface temperature anomalies (SSTAs) in these regions affect the WNPSH are elaborated. The formation mechanisms for the SSTAs in these five regions are discussed. Strengths and weaknesses of the climate models in simulating and predicting the WNPSH are also documented. Finally, key scientific problems deserving further studies are proposed.展开更多
A global atmospheric general circulation model (L9R15 AGCMs) forced by COADS SST was integrated from 1945 to 1993. Interannual and interdecadal variability of the simulated surface wind over the tropical Pacific was a...A global atmospheric general circulation model (L9R15 AGCMs) forced by COADS SST was integrated from 1945 to 1993. Interannual and interdecadal variability of the simulated surface wind over the tropical Pacific was analyzed and shown to agree vey well with observation. Simulation of surface wind over the central-western equatorial Pacific was more successful than that over the eastern Pacific. Zonal propagating feature of interannual variability of the tropical Pacific wind anomalies and its decadal difference were also simulated successfully. The close agreement between simulation and observation on the existence of obvious interdecadal variability of tropical Pacific surface wind attested to the high simulation capability of AGCM.展开更多
We applied a season-reliant empirical orthogonal function(S-EOF) analysis based on the results of the Community Earth System Model, version 1-Biogeochemistry, to seasonal mean air-sea CO_2 flux over the western North ...We applied a season-reliant empirical orthogonal function(S-EOF) analysis based on the results of the Community Earth System Model, version 1-Biogeochemistry, to seasonal mean air-sea CO_2 flux over the western North Pacific(WNP)(0°–35°N, 110°E–150°E). The first leading mode accounts for 29% of the total interannual variance, corresponding to the evolution of the El Ni-Southern Oscillation(ENSO) from its developing to decaying phases. During the ENSO developing phase in the summer and fall, the contribution of surface seawater CO_2 partial pressure anomalies is greater than that of gas transfer/solubility anomalies, which contribute to increasing oceanic CO_2 uptake over the WNP. During the ENSO mature phase in the winter, the anomalous southwesterly northwest of the western North Pacific anticyclone(WNPAC) reduces the surface wind speed in the China marginal sea and thus decreases oceanic CO_2 uptake by reducing the gas transfer coefficient. In the subsequent spring, the WNPAC maintains with an eastward shift in position. The anomalous southwesterly warms sea surface temperatures in the China marginal sea by reducing evaporation and thus decreases oceanic CO_2 uptake by enhancing surface seawater CO_2 partial pressure. This process, rather than the effect of decreasing gas transfer coefficient, dominates CO_2 flux anomalies in the spring.展开更多
Using hindcasts of the Beijing Climate Center Climate System Model, the relationships between interannual variability (IAV) and intraseasonal variability (ISV) of the Asian-western Pacific summer monsoon are diagn...Using hindcasts of the Beijing Climate Center Climate System Model, the relationships between interannual variability (IAV) and intraseasonal variability (ISV) of the Asian-western Pacific summer monsoon are diagnosed. Predictions show reasonable skill with respect to some basic characteristics of the ISV and IAV of the western North Pacific summer monsoon (WNPSM) and the Indian summer monsoon (ISM). However, the links between the seasonally averaged ISV (SAISV) and seasonal mean of ISM are overestimated by the model. This deficiency may be partially attributable to the overestimated frequency of long breaks and underestimated frequency of long active spells of ISV in normal ISM years, although the model is capable of capturing the impact of ISV on the seasonal mean by its shift in the probability of phases. Furthermore, the interannual relationships of seasonal mean, SAISV, and seasonally averaged long-wave variability (SALWV; i.e., the part with periods longer than the intraseasonal scale) of the WNPSM and ISM with SST and low-level circulation are examined. The observed seasonal mean, SAISV, and SALWV show similar correlation patterns with SST and atmospheric circulation, but with different details. However, the model presents these correlation distributions with unrealistically small differences among different scales, and it somewhat overestimates the teleconnection between monsoon and tropical central-eastern Pacific SST for the ISM, but underestimates it for the WNPSM, the latter of which is partially related to the too-rapid decrease in the impact of E1 Nifio-Southern Oscillation with forecast time in the model.展开更多
The relationship between the boreal winter (December, January, February) Aleutian Low (AL) and the simultaneous Australian summer monsoon (ASM) is explored in this study. A significant correlation is found betwe...The relationship between the boreal winter (December, January, February) Aleutian Low (AL) and the simultaneous Australian summer monsoon (ASM) is explored in this study. A significant correlation is found between the North Pacific index (NPI) and ASM index, the bulk of which is attributed to the significant correlation after late 1970s. Significant differences in precipitation and outgoing long-wave radiation between typical negative and positive NPI years appear over the ASM area. A regression analysis of the circulation pattern against the NPI during the three months is performed separately. We propose that the NPI is related with the ASM circulation possibly through the changes in the upper level westerly jet. In a typical negative NPI (strong Aleutian Low) year, the jet is greatly reinforced and the anomalous anticyclonic circulation to the south is thus excited, from which the easterly wind anomalies flowing into the ASM region emanate. Further, strong sinking motion over the northern entrance region of the jet is enhanced, and the local Hadley circulation anomaly between the ASM region and the coast of East Asia is strengthened. In this way, anomalous upward motion over the ASM area can thus be strengthened, and the convective activity intensified. Then the monsoon rainfall over ASM area is increased. An "asymmetric" connection between AL and the monsoon is found in this study.展开更多
Interdecadal and interannual timescales are dominant in the North China rainfall in rainy season (July and August). On the interdecadal timescale, the North China rainfall exhibited an abrupt decrease at the end of 19...Interdecadal and interannual timescales are dominant in the North China rainfall in rainy season (July and August). On the interdecadal timescale, the North China rainfall exhibited an abrupt decrease at the end of 1970s. In this study, we examined the effect of this abrupt rainfall decrease on the association between rainfall and circulation on the interannual timescale, and found that the interdecadal variation does not change the physical mechanism responsible for the interannual variation of North China rainfall. There is a linear relationship between the interdecadal and interannual variabilities of North China rainfall in rainy season.展开更多
The rainfall in North China during rainy sea-son (July and August (JA)) exhibits a strong interannual variability. In this study, the atmospheric circulation and SST anomalies associated with the interannual variation...The rainfall in North China during rainy sea-son (July and August (JA)) exhibits a strong interannual variability. In this study, the atmospheric circulation and SST anomalies associated with the interannual variation of JA North China rainfall are examined. It is found that on the interannual timescale, the JA North China rainfall is associ-ated with significant SST anomalies in the equatorial eastern Pacific, and the North China rainfall and SST anomaly in the equatorial eastern Pacific correspond to the similar variation of the upper-level westerly jet stream over East Asia. A pos-sible mechanism is proposed for the influence of the SST anomalies in the equatorial eastern Pacific on the North China rainfall.展开更多
Upper Circumpolar Deep Water(UCDW)and North Pacifi c Deep Water(NPDW)coexist in the upper deep layer(i.e.,with a 1.2-2.0-℃potential temperature range and a 2000-4100-dbar pressure range)of the Eastern Philippine Sea....Upper Circumpolar Deep Water(UCDW)and North Pacifi c Deep Water(NPDW)coexist in the upper deep layer(i.e.,with a 1.2-2.0-℃potential temperature range and a 2000-4100-dbar pressure range)of the Eastern Philippine Sea.They have similar properties in potential temperature and salinity,while have a signifi cant diff erence in dissolved silicate.Based on the repeated observations along a 137°E transect from the World Ocean Database(WOD18),this study revealed the interannual variability of dissolved silicate in the upper deep layer of the Eastern Philippine Sea.Dissolved silicate increased in 1995,1996,2005,2006,and 2007,and decreased in 1997,2000,2001,2002,and 2004.Composition analysis showed that the large diff erence between positive and negative dissolved silicate anomalies occurred mainly at~15°N and north of 25°N,with the concentration reaching 4.25μmol/g.Further analysis indicated that the interannual dissolved silicate variability was related to the zonal current variation in the upper deep layer.The relatively strong(weak)westward current transport increased(decreased)NPDW to the Eastern Philippine Sea,thereby resulting in increased(decreased)dissolved silicate.展开更多
基金This work was supported by the National Natural Science Foundation of China(Grant No:41776031)the National Key Research and Development Program of China(Grant 2018YFC1506903)+1 种基金the team project funding of scientific research innovation for universities in Guangdong province(Grant 2019KCXTF021)the program for scientific research start-up funds of Guangdong Ocean University(Grant R17051).
文摘The western North Pacific summer monsoon(WNPSM)is an important subcomponent of the Asian summer monsoon.The equatorial zonal wind(EZW)in the lower troposphere over the western Pacific may play a critical role in the evolution of the El Niño-Southern Oscillation(ENSO).The possible linkage between the EZW over the western Pacific and the offequatorial monsoonal winds associated with the WNPSM and its decadal changes have not yet been fully understood.Here,we find a non-stationary relationship between the WNPSM and the western Pacific EZW,significantly strengthening their correlation around the late 1980s/early 1990s.This observed shift in the WNPSM–EZW relationship could be explained by the changes in the related sea surface temperature(SST)configurations across the tropical oceans.The enhanced influence from the springtime tropical North Atlantic,summertime tropical central Pacific,and maritime continent SST anomalies may be working together in contributing to the recent intensified WNPSM–EZW co-variability.The observed recent strengthening of the WNPSM–EZW relationship may profoundly impact the climate system,including prompting more effective feedback from the WNPSM on subsequent ENSO evolution and bolstering a stronger biennial tendency of the WNPSM–ENSO coupled system.The results obtained herein imply that the WNPSM,EZW,ENSO,and the tropical North Atlantic SST may be closely linked within a unified climate system with a quasi-biennial rhythm occurring during recent decades,accompanied by a reinforcement of the WNPSM–ENSO interplay quite possibly triggered by enhanced tropical Pacific–Atlantic cross-basin interactions.These results highlight the importance of the tropical Atlantic cross-basin influences in shaping the spatial structure of WNPSM-related wind anomalies and the WNPSM–ENSO interaction.
基金National Key R&D Program of China(2016YFA0600601)Guangdong Basic and Applied Basic Research Foundation(2020A1515011572)Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies(2020B1212060025)。
文摘This study reveals that the interannual variability of the western edge of the western North Pacific(WNP)subtropical high(WNPSH)in early summer experienced an interdecadal decrease around 1990.Correspondingly,the zonal movement of the WNPSH and the zonal extension of the high-pressure anomaly over the WNP(WNPHA)in abnormal years possess smaller ranges after 1990.The different influences of the tropical SSTAs are important for this interdecadal change,which exhibit slow El Nino decaying pattern before 1990 while rapid transformation from El Nino to La Nina after 1990.The early summer tropical SSTAs and the relevant atmospheric circulation anomalies present obvious interdecadal differences.Before 1990,the warm SSTAs over the northern Indian Ocean and southern South China Sea favor the WNPHA through eastward-propagating Kelvin wave and meridional-vertical circulation,respectively.Meanwhile,the warm SSTA over the tropical central Pacific induces anomalous ascent to its northwest through the Gill response,which could strengthen the anomalous descent over the WNP through meridional-vertical circulation and further favor the eastward extension of the WNPHA to central Pacific.After 1990,the warm SSTAs over the Maritime Continent and northern Indian Ocean cause the WNPHA through meridional-vertical and zonal-vertical circulation,respectively.Overall,the anomalous warm SSTs and ascent and the resultant anomalous descent over the WNP are located more westward and southward after 1990 than before 1990.Consequently,the WNPHA features narrower zonal range and less eastward extension after 1990,corresponding to the interdecadal decease in the interannual variability of the western edge of the WNPSH.On the other hand,the dominant oscillation period of ENSO experienced an interdecadal reduction around 1990,contributing to the change of the El Nino SSTA associated with the anomalous WNPSH from slow decaying type to rapid transformation type.
基金supported by the National Natural Science Foundation of China (Grant No 40505019)
文摘The observed tropospheric biennial oscillation (TBO) in the western North Pacific (WNP) monsoon region has an interdecadal variability with a period of 40-50 yr. That suggests a weaker effect of the TBO on the East Asia followed by a stronger one. A simple analytic model was designed to investigate the mechanism of the interdecadal variability of the TBO. The results indicated that a local TBO air-sea system not only supports the TBO variability in the WNP monsoon region but also produces an interdecadal variability of the TBO.
基金This work wassupported by the National Science Foundation of China (NSFC) under contract Nos 40233028 and 40425009.
文摘The simulation of a higher-resolution oceanic GCM forced with COADS surface conditions during 1945 ~ 1993 was analyzed with insight into how the North Pacific responds to the surface forcing. The decadal-to-interdecadal variabilities in the thermal and dynamical fields especially those associated with the 1976/1977 regime shift in the North Pacific were investigated. The model successfully captures the dominant SST anomaly mode on the decadal-to-interdecadal time scales as well as the major feature of SST anomalies in the 1976/1977 regime shift. The model also successfully reproduces two typical subduction events that link the tropical and extratropical oceanic temperature anomalies during the 1970s and the 1980s. Most importantly, the model simulates the dynamical adjustment of the upper ocean under the surface wind forcing. The typical surface circulation anomaly is characterized by a pattern that is simultaneously related to the wind stress anomalies. The typical anomalous pattern for the entire upper-ocean is characterized by coherent anomalies of two oceanic gyres, i.e. , the subtropical and subpolar gyres. The delayed response and slower adjustment of the gyres, especially of the subpolar gyre, give rise to a persistent SST anomaly in the central North Pacific. The upper-ocean heat budgets in three target regions, i.e. , the central North Pacific, the Californian coastal region and the KOE region, are examined. The cooling in the central North Pacific around 1976/1977 is attributed to the heat flux and mefidional advection anomalies. The associated warming in the Californian coastal region is only due to the heat flux anomaly. A cooling shift in the KOE region which lags that in the central basin by 3 to 4 a is largely due to the meridional advection anomaly and the heat flux acts only as a damping role.
基金supported by the National Natural Science Foundation of China[grant number 42025502]the Guangdong Major Project of Basic and Applied Basic Research[grant number 2020B0301030004].
基金supported by the National Key Research and Development Program of China [grant number2018YFC1506903]the National Natural Science Foundation of China [grant number 41776031]+2 种基金the Guangdong Natural Science Foundation [grant number 2015A030313796]the program for scientific research start-up funds of Guangdong Ocean Universitythe Foundation for Returned Scholars of the Ministry of Education of China
基金Supported by the National Basic Research Program of China(2014CB953901)National Natural Science Foundation of China(41330423 and 41375095)Natural Science Foundation of Guangdong Province,China(2014A030310432)
文摘The western North Pacific subtropical high (WNPSH) is an important circulation system that impacts the East Asian summer climate. The interannual variability of the WNPSH is modulated by tropical air-sea interaction. In order to make it clear which oceanic regions are crucial to the interannual variability of the WNPSH, the research progresses in this regard in the past decade are reviewed. Based on the review, it is recognized that five oceanic regions are responsible for the interannual variability of the WNPSH in summer, including the equatorial central-eastern Pacific Ocean, tropical Indian Ocean, subtropical western North Pacific, the vicinity of the maritime continent, and the tropical Atlantic Ocean. The mechanisms how the sea surface temperature anomalies (SSTAs) in these regions affect the WNPSH are elaborated. The formation mechanisms for the SSTAs in these five regions are discussed. Strengths and weaknesses of the climate models in simulating and predicting the WNPSH are also documented. Finally, key scientific problems deserving further studies are proposed.
文摘A global atmospheric general circulation model (L9R15 AGCMs) forced by COADS SST was integrated from 1945 to 1993. Interannual and interdecadal variability of the simulated surface wind over the tropical Pacific was analyzed and shown to agree vey well with observation. Simulation of surface wind over the central-western equatorial Pacific was more successful than that over the eastern Pacific. Zonal propagating feature of interannual variability of the tropical Pacific wind anomalies and its decadal difference were also simulated successfully. The close agreement between simulation and observation on the existence of obvious interdecadal variability of tropical Pacific surface wind attested to the high simulation capability of AGCM.
基金supported by the National Natural Science Foundation of China(Grant Nos.41330423,41420104006)Jiangsu Collaborative Innovation Center for Climate Change
文摘We applied a season-reliant empirical orthogonal function(S-EOF) analysis based on the results of the Community Earth System Model, version 1-Biogeochemistry, to seasonal mean air-sea CO_2 flux over the western North Pacific(WNP)(0°–35°N, 110°E–150°E). The first leading mode accounts for 29% of the total interannual variance, corresponding to the evolution of the El Ni-Southern Oscillation(ENSO) from its developing to decaying phases. During the ENSO developing phase in the summer and fall, the contribution of surface seawater CO_2 partial pressure anomalies is greater than that of gas transfer/solubility anomalies, which contribute to increasing oceanic CO_2 uptake over the WNP. During the ENSO mature phase in the winter, the anomalous southwesterly northwest of the western North Pacific anticyclone(WNPAC) reduces the surface wind speed in the China marginal sea and thus decreases oceanic CO_2 uptake by reducing the gas transfer coefficient. In the subsequent spring, the WNPAC maintains with an eastward shift in position. The anomalous southwesterly warms sea surface temperatures in the China marginal sea by reducing evaporation and thus decreases oceanic CO_2 uptake by enhancing surface seawater CO_2 partial pressure. This process, rather than the effect of decreasing gas transfer coefficient, dominates CO_2 flux anomalies in the spring.
基金supported by the National Natural Science Foundation of China (Grant Nos.41305057, 41275076, 41105069, and 41375081)the National Basic Research Program of China (Grant Nos.2010CB951903 and 2014CB953900)the LCS Youth Fund (2014)
文摘Using hindcasts of the Beijing Climate Center Climate System Model, the relationships between interannual variability (IAV) and intraseasonal variability (ISV) of the Asian-western Pacific summer monsoon are diagnosed. Predictions show reasonable skill with respect to some basic characteristics of the ISV and IAV of the western North Pacific summer monsoon (WNPSM) and the Indian summer monsoon (ISM). However, the links between the seasonally averaged ISV (SAISV) and seasonal mean of ISM are overestimated by the model. This deficiency may be partially attributable to the overestimated frequency of long breaks and underestimated frequency of long active spells of ISV in normal ISM years, although the model is capable of capturing the impact of ISV on the seasonal mean by its shift in the probability of phases. Furthermore, the interannual relationships of seasonal mean, SAISV, and seasonally averaged long-wave variability (SALWV; i.e., the part with periods longer than the intraseasonal scale) of the WNPSM and ISM with SST and low-level circulation are examined. The observed seasonal mean, SAISV, and SALWV show similar correlation patterns with SST and atmospheric circulation, but with different details. However, the model presents these correlation distributions with unrealistically small differences among different scales, and it somewhat overestimates the teleconnection between monsoon and tropical central-eastern Pacific SST for the ISM, but underestimates it for the WNPSM, the latter of which is partially related to the too-rapid decrease in the impact of E1 Nifio-Southern Oscillation with forecast time in the model.
基金supported by the National Natural Science Foundation of China under Grant No. 40631005the Major State Basic Research Development Program of China (973 Program) under Grant No. 2009CB421406the Chinese Academy of Sciences Partnership Program
文摘The relationship between the boreal winter (December, January, February) Aleutian Low (AL) and the simultaneous Australian summer monsoon (ASM) is explored in this study. A significant correlation is found between the North Pacific index (NPI) and ASM index, the bulk of which is attributed to the significant correlation after late 1970s. Significant differences in precipitation and outgoing long-wave radiation between typical negative and positive NPI years appear over the ASM area. A regression analysis of the circulation pattern against the NPI during the three months is performed separately. We propose that the NPI is related with the ASM circulation possibly through the changes in the upper level westerly jet. In a typical negative NPI (strong Aleutian Low) year, the jet is greatly reinforced and the anomalous anticyclonic circulation to the south is thus excited, from which the easterly wind anomalies flowing into the ASM region emanate. Further, strong sinking motion over the northern entrance region of the jet is enhanced, and the local Hadley circulation anomaly between the ASM region and the coast of East Asia is strengthened. In this way, anomalous upward motion over the ASM area can thus be strengthened, and the convective activity intensified. Then the monsoon rainfall over ASM area is increased. An "asymmetric" connection between AL and the monsoon is found in this study.
基金supported by the Key Project of the Chinese Academy of Sciences(Grant No.KZCX2-203)the National Natural Science Foundation of China(Grant Nos.40075016 and 40023001).
文摘Interdecadal and interannual timescales are dominant in the North China rainfall in rainy season (July and August). On the interdecadal timescale, the North China rainfall exhibited an abrupt decrease at the end of 1970s. In this study, we examined the effect of this abrupt rainfall decrease on the association between rainfall and circulation on the interannual timescale, and found that the interdecadal variation does not change the physical mechanism responsible for the interannual variation of North China rainfall. There is a linear relationship between the interdecadal and interannual variabilities of North China rainfall in rainy season.
基金supported by the Chinese Acad-emy of Sciences(Grant Nos.KZCX3-SW-221 and KZCX3-SW-218)the National Natural Science Foundation of China(Grant No.40221503).
文摘The rainfall in North China during rainy sea-son (July and August (JA)) exhibits a strong interannual variability. In this study, the atmospheric circulation and SST anomalies associated with the interannual variation of JA North China rainfall are examined. It is found that on the interannual timescale, the JA North China rainfall is associ-ated with significant SST anomalies in the equatorial eastern Pacific, and the North China rainfall and SST anomaly in the equatorial eastern Pacific correspond to the similar variation of the upper-level westerly jet stream over East Asia. A pos-sible mechanism is proposed for the influence of the SST anomalies in the equatorial eastern Pacific on the North China rainfall.
基金Supported by the National Key Research and Development Program of China(No.2018YFC0309800)the National Natural Science Foundation of China(Nos.42176021,91858203)+1 种基金the Open Project Program of State Key Laboratory of Tropical Oceanography(No.LTOZZ2001)the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(No.GML2019ZD0304)。
文摘Upper Circumpolar Deep Water(UCDW)and North Pacifi c Deep Water(NPDW)coexist in the upper deep layer(i.e.,with a 1.2-2.0-℃potential temperature range and a 2000-4100-dbar pressure range)of the Eastern Philippine Sea.They have similar properties in potential temperature and salinity,while have a signifi cant diff erence in dissolved silicate.Based on the repeated observations along a 137°E transect from the World Ocean Database(WOD18),this study revealed the interannual variability of dissolved silicate in the upper deep layer of the Eastern Philippine Sea.Dissolved silicate increased in 1995,1996,2005,2006,and 2007,and decreased in 1997,2000,2001,2002,and 2004.Composition analysis showed that the large diff erence between positive and negative dissolved silicate anomalies occurred mainly at~15°N and north of 25°N,with the concentration reaching 4.25μmol/g.Further analysis indicated that the interannual dissolved silicate variability was related to the zonal current variation in the upper deep layer.The relatively strong(weak)westward current transport increased(decreased)NPDW to the Eastern Philippine Sea,thereby resulting in increased(decreased)dissolved silicate.