The relationships between ENSO and the East Asian-western North Pacific monsoon simulated by the Flexible Global Ocean-Atmosphere-Land System model, Spectral Version 2 （FGOALS-s2）, a state-of-the-art coupled general...The relationships between ENSO and the East Asian-western North Pacific monsoon simulated by the Flexible Global Ocean-Atmosphere-Land System model, Spectral Version 2 （FGOALS-s2）, a state-of-the-art coupled general circulation model （CGCM）, are evaluated. For E1 Nino developing summers, FGOALS-s2 reproduces the anomalous cyclone over the western North Pacific （WNP） and associated negative precipita- tion anomalies in situ. In the observation, the anomalous cyclone is transformed to an anomalous anticyclone over the WNP （WNPAC） during E1 Nifio mature winters. The model reproduces the WNPAC and associated positive precipitation anomalies over southeastern China during winter. However, the model fails to simu- late the asymmetry of the wintertime circulation anomalies over the WNP between E1 Nifio and La Nifia. The simulated anomalous cyclone over the WNP （WNPC） associated with La Nifia is generally symmetric about the WNPAC associated with E1 Nifio, rather than shifted westward as that in the observation. The discrepancy can partially explain why simulated La Nifia events decay much faster than observed. In the observation, the WNPAC maintains throughout the E1 Nifio decaying summer under the combined effects of local forcing of the WNP cold sea surface temperature anomaly （SSTA） and remote forcing from basin- wide warming in the tropical Indian Ocean. FGOALS-s2 captures the two mechanisms and reproduces the WNPAC throughout the summer. However, owing to biases in the mean state, the precipitation anomalies over East Asia, especially those of the Meiyu rain belt, are much weaker than that in the observation.展开更多
Timing of uplift of the Tibetan Plateau is a fundamental work to understand global climatic change and mountain\|building mechanism. Because most of the evidence comes from the Himalaya\|South Tibet, the northern marg...Timing of uplift of the Tibetan Plateau is a fundamental work to understand global climatic change and mountain\|building mechanism. Because most of the evidence comes from the Himalaya\|South Tibet, the northern margin of the Plateau may hold the key to unravel a whole view of the Plateau uplift history, in which basin sediments are the most important part because they have continuously recorded the history of pure surface uplift in related mountains. In the whole foredeep bordered by the North Marginal Thrust (Kunlun—Altun—Qilian—Longmen Trusts) along the northern and eastern Tibetan Plateau, thick Cenozoic stratigraphy is widely distributed and records the whole history of the Plateau uplift process. It can be lithologically divided in three large units from top to bottom: light colored sediments, boulder conglomerate and red bed. The red bed is mostly fine sediments of lacustrine and/or fluviolacustrine origins and the boulder conglomerate has been long thought as evidence of rapid uplift of the Tibetan Plateau. The light colored sediments are mostly eolian and/or fluviolacustrine deposits or desert\|gobi sediments. Thus, to date the boulder conglomerate holds the key to unravel the Plateau uplift. We chose the Linxia Basin in the northeastern Tibetan Plateau and Jiuquan Basin in the northern Qilian Mountains as two pilot controlling sites to reconstruct the history of uplift process of the Tibetan Plate au and its accompanied climatic change and to see if a coupling process would ex ist between the uplift of the Plateau and Asian monsoon system.展开更多
This paper analyzes the possible influence of boreal winter Arctic Oscillation/North Atlantic Oscillation （AO/ NAO） on the Indian Ocean upper ocean heat content in summer as well as the summer monsoonal circulation....This paper analyzes the possible influence of boreal winter Arctic Oscillation/North Atlantic Oscillation （AO/ NAO） on the Indian Ocean upper ocean heat content in summer as well as the summer monsoonal circulation. The strong interannual co-variation between winter 1000-hPa geopotential height in the Northern Hemisphere and sum- mer ocean heat content in the uppermost 120 m over the tropical Indian Ocean was investigated by a singular decom- position analysis for the period 1979-2014. The second paired-modes explain 23.8% of the squared covariance, and reveal an AO/NAO pattern over the North Atlantic and a warming upper ocean in the western tropical Indian Ocean. The positive upper ocean heat content enhances evaporation and convection, and results in an anomalous meridional circulation with ascending motion over 5°S-5°N and descending over 15°-25°N. Correspondingly, in the lower tro- posphere, significantly anomalous northerly winds appear over the western Indian Ocean north of the equator, imply- ing a weaker summer monsoon circulation. The off-equator oceanic Rossby wave plays a key role in linking the AO/NAO and the summer heat content anomalies. In boreal winter, a positive AO/NAO triggers a down-welling Rossby wave in the central tropical Indian Ocean through the atmospheric teleconnection. As the Rossby wave ar- rives in the western Indian Ocean in summer, it results in anomalous upper ocean heating near the equator mainly through the meridional advection. The AO/NAO-forced Rossby wave and the resultant upper ocean warming are well reproduced by an ocean circulation model. The winter AO/NAO could be a potential season-lead driver of the sum- mer atmospheric circulation over the northwestern Indian Ocean.展开更多
Climatologically, June is usually the wettest month in Hong Kong. With significant interannual variation of the summer monsoon, the rainfall variability in June is also large. As Hong Kong is in close proximity to the...Climatologically, June is usually the wettest month in Hong Kong. With significant interannual variation of the summer monsoon, the rainfall variability in June is also large. As Hong Kong is in close proximity to the peripheries of different monsoon regions, the variability of June rainfall largely depends on the relative strength of various monsoon systems. In the present study, a new index comparing the relative condition of the western North Pacific summer monsoon and the South China Sea summer monsoon is developed based on the difference between the respective monsoon indices WNPMI （western North Pacific summer monsoon index） and UMI （unified monsoon index）. It is shown that June rainfall in Hong Kong and its vicinity is better correlated with this new index than either WNPMI or UMI alone. Based on the signs of the new index in conjunction with those of WNPMI and UMI, a framework to stratify the monsoon conditions into different configurations together with a simple scheme to summarize the associated rainfall responses is formulated. This study highlights how the rainfall variability on a local or regional scale can be quantified by the broad-scale conditions of different monsoon systems.展开更多
基金supported by the Chinese Academy of Sciences Strategic Priority Research Program(Grant No.XDA05110305)the National Program on Key Basic Research Project(2010CB951904)+2 种基金the National Natural Science Foundation of China(Grant Nos.41005040,41023002 and 40890054)the National High-Tech Research and Development Plan of China(2010AA012302)the China Meteorological Administration(Grant No.GYHY201006019)
文摘The relationships between ENSO and the East Asian-western North Pacific monsoon simulated by the Flexible Global Ocean-Atmosphere-Land System model, Spectral Version 2 （FGOALS-s2）, a state-of-the-art coupled general circulation model （CGCM）, are evaluated. For E1 Nino developing summers, FGOALS-s2 reproduces the anomalous cyclone over the western North Pacific （WNP） and associated negative precipita- tion anomalies in situ. In the observation, the anomalous cyclone is transformed to an anomalous anticyclone over the WNP （WNPAC） during E1 Nifio mature winters. The model reproduces the WNPAC and associated positive precipitation anomalies over southeastern China during winter. However, the model fails to simu- late the asymmetry of the wintertime circulation anomalies over the WNP between E1 Nifio and La Nifia. The simulated anomalous cyclone over the WNP （WNPC） associated with La Nifia is generally symmetric about the WNPAC associated with E1 Nifio, rather than shifted westward as that in the observation. The discrepancy can partially explain why simulated La Nifia events decay much faster than observed. In the observation, the WNPAC maintains throughout the E1 Nifio decaying summer under the combined effects of local forcing of the WNP cold sea surface temperature anomaly （SSTA） and remote forcing from basin- wide warming in the tropical Indian Ocean. FGOALS-s2 captures the two mechanisms and reproduces the WNPAC throughout the summer. However, owing to biases in the mean state, the precipitation anomalies over East Asia, especially those of the Meiyu rain belt, are much weaker than that in the observation.
文摘Timing of uplift of the Tibetan Plateau is a fundamental work to understand global climatic change and mountain\|building mechanism. Because most of the evidence comes from the Himalaya\|South Tibet, the northern margin of the Plateau may hold the key to unravel a whole view of the Plateau uplift history, in which basin sediments are the most important part because they have continuously recorded the history of pure surface uplift in related mountains. In the whole foredeep bordered by the North Marginal Thrust (Kunlun—Altun—Qilian—Longmen Trusts) along the northern and eastern Tibetan Plateau, thick Cenozoic stratigraphy is widely distributed and records the whole history of the Plateau uplift process. It can be lithologically divided in three large units from top to bottom: light colored sediments, boulder conglomerate and red bed. The red bed is mostly fine sediments of lacustrine and/or fluviolacustrine origins and the boulder conglomerate has been long thought as evidence of rapid uplift of the Tibetan Plateau. The light colored sediments are mostly eolian and/or fluviolacustrine deposits or desert\|gobi sediments. Thus, to date the boulder conglomerate holds the key to unravel the Plateau uplift. We chose the Linxia Basin in the northeastern Tibetan Plateau and Jiuquan Basin in the northern Qilian Mountains as two pilot controlling sites to reconstruct the history of uplift process of the Tibetan Plate au and its accompanied climatic change and to see if a coupling process would ex ist between the uplift of the Plateau and Asian monsoon system.
基金Supported by the National Natural Science Foundation of China(41375071)Project PE16010 of the Korea Polar Research Institute
文摘This paper analyzes the possible influence of boreal winter Arctic Oscillation/North Atlantic Oscillation （AO/ NAO） on the Indian Ocean upper ocean heat content in summer as well as the summer monsoonal circulation. The strong interannual co-variation between winter 1000-hPa geopotential height in the Northern Hemisphere and sum- mer ocean heat content in the uppermost 120 m over the tropical Indian Ocean was investigated by a singular decom- position analysis for the period 1979-2014. The second paired-modes explain 23.8% of the squared covariance, and reveal an AO/NAO pattern over the North Atlantic and a warming upper ocean in the western tropical Indian Ocean. The positive upper ocean heat content enhances evaporation and convection, and results in an anomalous meridional circulation with ascending motion over 5°S-5°N and descending over 15°-25°N. Correspondingly, in the lower tro- posphere, significantly anomalous northerly winds appear over the western Indian Ocean north of the equator, imply- ing a weaker summer monsoon circulation. The off-equator oceanic Rossby wave plays a key role in linking the AO/NAO and the summer heat content anomalies. In boreal winter, a positive AO/NAO triggers a down-welling Rossby wave in the central tropical Indian Ocean through the atmospheric teleconnection. As the Rossby wave ar- rives in the western Indian Ocean in summer, it results in anomalous upper ocean heating near the equator mainly through the meridional advection. The AO/NAO-forced Rossby wave and the resultant upper ocean warming are well reproduced by an ocean circulation model. The winter AO/NAO could be a potential season-lead driver of the sum- mer atmospheric circulation over the northwestern Indian Ocean.
文摘Climatologically, June is usually the wettest month in Hong Kong. With significant interannual variation of the summer monsoon, the rainfall variability in June is also large. As Hong Kong is in close proximity to the peripheries of different monsoon regions, the variability of June rainfall largely depends on the relative strength of various monsoon systems. In the present study, a new index comparing the relative condition of the western North Pacific summer monsoon and the South China Sea summer monsoon is developed based on the difference between the respective monsoon indices WNPMI （western North Pacific summer monsoon index） and UMI （unified monsoon index）. It is shown that June rainfall in Hong Kong and its vicinity is better correlated with this new index than either WNPMI or UMI alone. Based on the signs of the new index in conjunction with those of WNPMI and UMI, a framework to stratify the monsoon conditions into different configurations together with a simple scheme to summarize the associated rainfall responses is formulated. This study highlights how the rainfall variability on a local or regional scale can be quantified by the broad-scale conditions of different monsoon systems.
