In recent years, El Nino Modoki （a type of pseudo-El Nino） has been distinguished as a unique large-scale ocean warming phenomenon happening in the central tropical Pacific that is quite different from the tradition...In recent years, El Nino Modoki （a type of pseudo-El Nino） has been distinguished as a unique large-scale ocean warming phenomenon happening in the central tropical Pacific that is quite different from the traditional El Nino. In this study, EOF analysis was used to successfully separate El Nino and El Nino Modoki. The abilities of the NINO3 index, NINO3.4 index, NINO1＋2 index and NINO4 index in characterizing El Nino were explored in detail. The resulting suggestion was that, comparatively, NINO3 is the optimal index for monitoring El Nino among the four NINO indices, as the other NINO indices were found to be less good at distinguishing between El Nino and El Nino Modoki signals, or were easily disturbed by El Nino Modoki signals. Further, an improved El Nino Modoki index （IEMI） was introduced in the current paper to better represent the El Nino Modoki that is captured by the second leading EOF mode of monthly tropical Pacific sea surface temperature anomalies （SSTAs）. The IEMI is an improvement of the El Nino Modoki index （EMI） through adjustments made to the inappropriate weight coefficients of the three boxes of EMI. The IEMI therefore overcomes the EMI’s inability to monitor the two historical El Nino Modoki events, as well as avoids the possible risk （present in the EMI） of excluding the interference of the El Nino signal. The realistic and potential advantages of the IEMI are clear.展开更多
The present study revisited the first two leading modes of tropical Pacific sea surface temperature anomalies （SSTA） during the period of 1979-2008. It is suggested that the so-called El Nino Modoki, which is captur...The present study revisited the first two leading modes of tropical Pacific sea surface temperature anomalies （SSTA） during the period of 1979-2008. It is suggested that the so-called El Nino Modoki, which is captured by the second mode, exists objectively and exhibits obvious differences from traditional El Nifio, which is captured by the first mode, in terms of its spatial characteristics. Furthermore, the authors found that El Nino Modoki is linearly independent of traditional El Nino; hence, it cannot be described as part of the traditional El Nino evolution, and vice versa.展开更多
In the summers of 1998 and 2010, severe floods occurred in the middle and lower reaches of the Yangtze River. Although an El Nifio event took place preceding each of the summer floods, significant differences between ...In the summers of 1998 and 2010, severe floods occurred in the middle and lower reaches of the Yangtze River. Although an El Nifio event took place preceding each of the summer floods, significant differences between the two summer floods and the two E1 Nifio events were identified. The 1997/98 E1 Nifio is a conventional one with strongest warming in the central-eastern Pacific, whereas the 2009/10 event is an E1 Nifio Modoki with strongest warming in the central Pacific. In this study, summer rainfall anomalies （SRA） in the two years were first compared based on the rainfall data at 160 stations in China's Mainland, and a significant difference in SRA was found. To understand the underlying mechanism for the difference, the atmospheric circulation systems, particularly the western North Pacific anticyclone （WNPAC）, the western Pacific subtropical high （WPSH）, and the low-level air flows, were compared in the two years by using the NCEP/NCAR reanalysis data. The results display that the WNPAC was stronger in 2010 than in 1998, along with a northwestward shift, causing weakened southwesterly from the Bay of BengM to the South China Sea but intensified southerly in eastern China. This resulted in less water vapor transport from the tropical Indian Ocean and the South China Sea but more from the subtropical western Pacific to East Asia. Subsequently, the rainband in 2010 shifted northward. The difference in the WNPAC was causedby the anomalous ascending motion associated with the warming location in the two E1 Nifio events. ~rthermore, the role of tropical sea surface temperature （SST） in modulating these differences was investigated by conducting sensitivity experiments using GFDL AM2.1 （Geophysical Fluid Dynamics Laboratory Atmospheric Model）. Two experiments were performed, one with the observed monthly SST and the other with June SST persisting through the whole summer. The results suggest that the model well reproduced the primary differences in the atmospheric circulation systems in the two展开更多
The effects of E1Nifio Modoki events on global ozone concentrations are investigated from 1980 to 2010 E1 Nifio Modoki events cause a stronger Brewer-Dobson （BD） circulation which can transports more ozone-poor air ...The effects of E1Nifio Modoki events on global ozone concentrations are investigated from 1980 to 2010 E1 Nifio Modoki events cause a stronger Brewer-Dobson （BD） circulation which can transports more ozone-poor air from the troposphere to stratosphere, leading to a decrease of ozone inthe lower-middle stratosphere from 90~S to 90~N. These changes in ozone concentrations reduce stratospheric column ozone. The reduction in stratospheric column ozone during E1 Nifio Modoki events is more pronounced over the tropical eastern Pacific than over other tropical areas because transport of ozone-poor air from middle-high latitudes in both hemispheres to low latitudes is the strongest between 60°W and 120°W. Because of the decrease in stratospheric column ozone during E1 Nifio Modoki events more UV radiation reaches the tropical troposphere leading to significant increases in tropospheric column ozone An empirical orthogonal function （EOF） analysis of the time series from 1980 to 2010 of stratospheric and tropospheric ozone monthly anomalies reveals that： E1 Nifio Modoki events are associated with the primary EOF modes of both time series. We also found that E1 Nifio Modoki events can affect global ozone more significantly than canonical E1 Nifio events. These results imply that E1 Nifio Modoki is a key contributor to variations in global ozone from 1980 to 2010.展开更多
Interannual variability of landfalling tropical cyclones(TCs) in China during 1960-2010 is investigated.By using the method of partial least squares regression(PLS-regression),canonical ENSO and ENSO Modoki are identi...Interannual variability of landfalling tropical cyclones(TCs) in China during 1960-2010 is investigated.By using the method of partial least squares regression(PLS-regression),canonical ENSO and ENSO Modoki are identified to be the factors that contribute to the interannual variability of landfalling TCs.El Ni o Modoki years are associated with a greater-than-average frequency of landfalling TCs in China,but reversed in canonical El Ni o years.Significant difference in genesis locations of landfalling TCs in China for the two kinds of El Ni o phases occurs dominantly in the northern tropical western North Pacific(WNP).The patterns of low-level circulation anomalies and outgoing longwave radiation(OLR) anomalies associated with landfalling TC genesis with different types of El Ni o phases are examined.During canonical El Ni o years,a broad zonal band of positive OLR anomalies dominates the tropical WNP,while the circulation anomalies exhibit a meridionally symmetrical dipole pattern with an anticyclonic anomaly in the subtropics and a cyclonic anomaly near the tropics.In El Ni o Modoki years,a vast region of negative OLR anomalies,roughly to the south of 25°N with a strong large-scale cyclonic anomaly over the tropical WNP,provides a more favorable condition for landfalling TC genesis compared to its counterpart during canonical El Ni o years.For more landfalling TCs formed in the northern tropical WNP in El Ni o Modoki years,there are more TCs making landfall on the northern coast of China in El Ni o Modoki years than in canonical El Ni o years.The number of landfalling TCs is slightly above normal in canonical La Ni a years.Enhanced convection is found in the South China Sea(SCS) and the west of the tropical WNP,which results in landfalling TCs forming more westward in canonical La Ni a years.During La Ni a Modoki years,the landfalling TC frequency are below normal,owing to an unfavorable condition for TC genesis persisting in a broad zonal band from 5°N to 25°N.Since the western North Pacific subtropical hig展开更多
Using a new global ocean reanalysis of the second generation Global Ocean Data Assimilation System of the Beijing Climate Center(BCC_GODAS2.0) spanning the period 1990-2009,we firstly quantify the accuracy of BCC_GODA...Using a new global ocean reanalysis of the second generation Global Ocean Data Assimilation System of the Beijing Climate Center(BCC_GODAS2.0) spanning the period 1990-2009,we firstly quantify the accuracy of BCC_GODAS2.0 in representing the temperature and salinity by comparing with OISST and SODA data.The results show that the assimilation system may effectively improve the estimations of temperature and salinity by assimilating all kinds of observations,especially in the equatorial eastern Pacific.Moreover,the root mean square errors of monthly temperature and salinity are respectively reduced by 0.53℃ and 0.28 psu,compared with the model control simulation results.Then,the applicability of this ocean reanalysis for sea surface temperature(SST) anomaly variability in the tropical Pacific is evaluated with the observational HadISST data.The NINO3 index of the new reanalysis shows a good agreement with that of HadISST,with a correlation of 93.6%.Variations in SST from BCC_GODAS2.0 are similar to those obtained from HadISST data along the equator,showing the major large zonal-scale features such as the strong magnitude of seasonal cycle.The amplitude of SST anomaly standard deviation in the equatorial eastern Pacific is also closer to observations(HadISST) than NCEP GODAS does.Besides,the first two leading empirical orthogonal function(EOF) modes of the monthly SST anomalies over the tropical Pacific region are explored.The EOF1 pattern of BCC_GODAS2.0 captures a traditional El Ni o pattern,which improves magnitudes of the positive SST anomaly in the cold tongue of the eastern Pacific.The EOF2 pattern exhibits a El Ni o Modoki pattern.Comparatively,the EOF2 pattern of BCC_GODAS2.0 extends more strongly toward the subtropics.It also overcomes the problem that negative loadings are confined in the narrow equatorial eastern Pacific.Consequently,the magnitude and spatial distribution of the leading EOF patterns of BCC_GODAS2.0 are well consistent with those of HadISST.展开更多
Based on a linear model, the present study provides analytical solutions for ideal triple forcing sources similar to sea surface temperature anomaly （SSTA） pat- terns associated with El Nino-Southern Oscillation （E...Based on a linear model, the present study provides analytical solutions for ideal triple forcing sources similar to sea surface temperature anomaly （SSTA） pat- terns associated with El Nino-Southern Oscillation （ENSO） Modoki in winter. The ideal triple pattern is composed of an equatorially symmetric heat source in the middle and equatoriaUy asymmetric cold forcing in the southeast and northwest. The equatorially symmetric heat source excites low-level cyclonic circulation anomalies associated with Rossby waves in both hemispheres, while the northwest- ern and southeastern equatorially asymmetric cold sources induce low-level anomalous anticyclones associated with Rossby waves in the hemisphere where the forcing source is located. Low-level zonal winds converge toward the heat sources associated with Kelvin and Rossby waves. Due to unequal forcing intensity in the northwest and southeast, atmospheric responses around the equatorially symmetric forcing become asymmetric, and low-level cyclonic circulation anomalies in the Southern Hemisphere become greater than those in the Northern Hemisphere. Ascending （descending） flows coincide with heat （cold） sources, resulting in a double-cell structure over the regions of forcing sources. Ideal triple patterns similar to SSTA patterns associated with La Nina Modoki produce opposite atmospheric responses. The theoretical atmospheric responses are consistent with observed circulation anomalies associated with ENSO Modoki. Therefore, the theoretical solutions can explain the dynamics responsible for atmospheric circulation anomalies associated with ENSO Modoki events.展开更多
Recent SST and atmospheric circulation anomaly data suggest that the 2015/16 El Nino event is quickly decaying. Some researchers have predicted a forthcoming La Nina event in late summer or early fall 2016. From the p...Recent SST and atmospheric circulation anomaly data suggest that the 2015/16 El Nino event is quickly decaying. Some researchers have predicted a forthcoming La Nina event in late summer or early fall 2016. From the perspective of the modulation of tropical SST by solar activity, the authors studied the evolution of the 2015/16 El Nino event, which occurred right after the 2014 solar peak year. Based on statistical and composite analysis, a significant positive correlation was found between sunspot number index and El Ni^o Modoki index, with a lag of two years. A clear evolution of El Nino Modoki events was found within 1-3 years following each solar peak year during the past 126 years, suggesting that anomalously strong solar activity during solar peak periods favors the triggering of an El Nino Modoki event. The patterns of seasonal mean SST and wind anomalies since 2014 are more like a mixture of two types of El Nino （i.e. eastern Pacific El Nino and El Nino Modoki）, which is similar to the pattern modulated by solar activity during the years following a solar peak. Therefore, the El Nino Modoki component in the 2015/16 El Nino event may be a consequence of solar activity, which probably will not decay as quickly as the eastern Pacific El Nino component. The positive SST anomaly will probably sustain in the central equatorial Pacific （around the dateline） and the northeastern Pacific along the coast of North America, with a low-intensity level, during the second half of 2016.展开更多
El Nio Modoki,similar to but different from canonical El Nio,has been observed since the late1970s.In this paper,using HadISST and NCEP/NCAR wind data,we analyze the relationship between El Nio Modoki and Sea Su...El Nio Modoki,similar to but different from canonical El Nio,has been observed since the late1970s.In this paper,using HadISST and NCEP/NCAR wind data,we analyze the relationship between El Nio Modoki and Sea Surface Temperature(SST)in the offshore area of China and its adjacent waters for different seasons.Our results show a significant negative correlation between El Nio Modoki in summer and SST in autumn in the offshore area of China and its adjacent waters,particularly for regions located in the east of the Kuroshio.It is also found that during El Nio Modoki period,anomalous northerlies prevail over the regions from the northern part of the Philippines to the offshore area of China,indicating that the northerlies are unfavorable for the transport of warm water from the western tropical Pacific to the mid-latitude area.Consequently,El Nio Modoki in summer may play a substantial role in cold SST anomalies in the offshore area of China and its adjacent waters in autumn through the influence of the Kuroshio,with a lagged response of the ocean to the atmospheric wind field.展开更多
A comparison of sensitivity in extratropical circulation in the Northern Hemisphere （NH） and Southern Hemisphere （SH） is conducted through observational analyses and diagnostic linear model experiments for two typ...A comparison of sensitivity in extratropical circulation in the Northern Hemisphere （NH） and Southern Hemisphere （SH） is conducted through observational analyses and diagnostic linear model experiments for two types of El Ni（n）o events,the traditional El Ni（n）o with the strongest warmth in the eastern tropical Pacific （EP El Ni（n）o） and the El Ni（n）o Modoki with the strongest warmth in the central tropical Pacific （CP El Ni（n）o）.It is shown that CP El Ni（n）o favors the occurrence of a negative-phase Northern Annular Mode （NAM）,while EP El Ni（n）o favors that of the Pacific-North American （PNA） pattern.In SH,both EP and CP El Ni（n）o induce a negative phase Southern Annular Mode （SAM）.However,the former has a greater amplitude,which is consistent with the stronger sea surface temperature （SST） warmth.The difference in the two types of El Ni（n）o events in NH may originate from the dependence of heating-induced extratropical response on the location of initial heating,which may be associated with activity of the stationary wave.In SH,the lack of sensitivity to the location of heating can be associated with weaker activity of the stationary wave therein.展开更多
基金supported by the National Natural Science Foun-dation of China (Grant Nos. 40675028 and 40975029)the National Basic Research Program of China (Grant No.2006CB403600)the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG)
文摘In recent years, El Nino Modoki （a type of pseudo-El Nino） has been distinguished as a unique large-scale ocean warming phenomenon happening in the central tropical Pacific that is quite different from the traditional El Nino. In this study, EOF analysis was used to successfully separate El Nino and El Nino Modoki. The abilities of the NINO3 index, NINO3.4 index, NINO1＋2 index and NINO4 index in characterizing El Nino were explored in detail. The resulting suggestion was that, comparatively, NINO3 is the optimal index for monitoring El Nino among the four NINO indices, as the other NINO indices were found to be less good at distinguishing between El Nino and El Nino Modoki signals, or were easily disturbed by El Nino Modoki signals. Further, an improved El Nino Modoki index （IEMI） was introduced in the current paper to better represent the El Nino Modoki that is captured by the second leading EOF mode of monthly tropical Pacific sea surface temperature anomalies （SSTAs）. The IEMI is an improvement of the El Nino Modoki index （EMI） through adjustments made to the inappropriate weight coefficients of the three boxes of EMI. The IEMI therefore overcomes the EMI’s inability to monitor the two historical El Nino Modoki events, as well as avoids the possible risk （present in the EMI） of excluding the interference of the El Nino signal. The realistic and potential advantages of the IEMI are clear.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40975029,40675028,and 40810059005)
文摘The present study revisited the first two leading modes of tropical Pacific sea surface temperature anomalies （SSTA） during the period of 1979-2008. It is suggested that the so-called El Nino Modoki, which is captured by the second mode, exists objectively and exhibits obvious differences from traditional El Nifio, which is captured by the first mode, in terms of its spatial characteristics. Furthermore, the authors found that El Nino Modoki is linearly independent of traditional El Nino; hence, it cannot be described as part of the traditional El Nino evolution, and vice versa.
基金Supported by the National Key Basic Research and Development (973) Program of China (2012CB417403)China Meteorological Administration Special Public Welfare Research Fund (GYHY201006022 and GYHY200906018)
文摘In the summers of 1998 and 2010, severe floods occurred in the middle and lower reaches of the Yangtze River. Although an El Nifio event took place preceding each of the summer floods, significant differences between the two summer floods and the two E1 Nifio events were identified. The 1997/98 E1 Nifio is a conventional one with strongest warming in the central-eastern Pacific, whereas the 2009/10 event is an E1 Nifio Modoki with strongest warming in the central Pacific. In this study, summer rainfall anomalies （SRA） in the two years were first compared based on the rainfall data at 160 stations in China's Mainland, and a significant difference in SRA was found. To understand the underlying mechanism for the difference, the atmospheric circulation systems, particularly the western North Pacific anticyclone （WNPAC）, the western Pacific subtropical high （WPSH）, and the low-level air flows, were compared in the two years by using the NCEP/NCAR reanalysis data. The results display that the WNPAC was stronger in 2010 than in 1998, along with a northwestward shift, causing weakened southwesterly from the Bay of BengM to the South China Sea but intensified southerly in eastern China. This resulted in less water vapor transport from the tropical Indian Ocean and the South China Sea but more from the subtropical western Pacific to East Asia. Subsequently, the rainband in 2010 shifted northward. The difference in the WNPAC was causedby the anomalous ascending motion associated with the warming location in the two E1 Nifio events. ~rthermore, the role of tropical sea surface temperature （SST） in modulating these differences was investigated by conducting sensitivity experiments using GFDL AM2.1 （Geophysical Fluid Dynamics Laboratory Atmospheric Model）. Two experiments were performed, one with the observed monthly SST and the other with June SST persisting through the whole summer. The results suggest that the model well reproduced the primary differences in the atmospheric circulation systems in the two
基金supported by the 973 Program (Grant No.2010CB950400)the National Natural Science Foundation of China (Grant Nos.41225018 and 41305036)
文摘The effects of E1Nifio Modoki events on global ozone concentrations are investigated from 1980 to 2010 E1 Nifio Modoki events cause a stronger Brewer-Dobson （BD） circulation which can transports more ozone-poor air from the troposphere to stratosphere, leading to a decrease of ozone inthe lower-middle stratosphere from 90~S to 90~N. These changes in ozone concentrations reduce stratospheric column ozone. The reduction in stratospheric column ozone during E1 Nifio Modoki events is more pronounced over the tropical eastern Pacific than over other tropical areas because transport of ozone-poor air from middle-high latitudes in both hemispheres to low latitudes is the strongest between 60°W and 120°W. Because of the decrease in stratospheric column ozone during E1 Nifio Modoki events more UV radiation reaches the tropical troposphere leading to significant increases in tropospheric column ozone An empirical orthogonal function （EOF） analysis of the time series from 1980 to 2010 of stratospheric and tropospheric ozone monthly anomalies reveals that： E1 Nifio Modoki events are associated with the primary EOF modes of both time series. We also found that E1 Nifio Modoki events can affect global ozone more significantly than canonical E1 Nifio events. These results imply that E1 Nifio Modoki is a key contributor to variations in global ozone from 1980 to 2010.
基金National Natural Science Foundation of China (41105036,41105035,40730948,40830958,40921160382)National Grand Fundamental Research "973" Program of China (2009CB421502)
文摘Interannual variability of landfalling tropical cyclones(TCs) in China during 1960-2010 is investigated.By using the method of partial least squares regression(PLS-regression),canonical ENSO and ENSO Modoki are identified to be the factors that contribute to the interannual variability of landfalling TCs.El Ni o Modoki years are associated with a greater-than-average frequency of landfalling TCs in China,but reversed in canonical El Ni o years.Significant difference in genesis locations of landfalling TCs in China for the two kinds of El Ni o phases occurs dominantly in the northern tropical western North Pacific(WNP).The patterns of low-level circulation anomalies and outgoing longwave radiation(OLR) anomalies associated with landfalling TC genesis with different types of El Ni o phases are examined.During canonical El Ni o years,a broad zonal band of positive OLR anomalies dominates the tropical WNP,while the circulation anomalies exhibit a meridionally symmetrical dipole pattern with an anticyclonic anomaly in the subtropics and a cyclonic anomaly near the tropics.In El Ni o Modoki years,a vast region of negative OLR anomalies,roughly to the south of 25°N with a strong large-scale cyclonic anomaly over the tropical WNP,provides a more favorable condition for landfalling TC genesis compared to its counterpart during canonical El Ni o years.For more landfalling TCs formed in the northern tropical WNP in El Ni o Modoki years,there are more TCs making landfall on the northern coast of China in El Ni o Modoki years than in canonical El Ni o years.The number of landfalling TCs is slightly above normal in canonical La Ni a years.Enhanced convection is found in the South China Sea(SCS) and the west of the tropical WNP,which results in landfalling TCs forming more westward in canonical La Ni a years.During La Ni a Modoki years,the landfalling TC frequency are below normal,owing to an unfavorable condition for TC genesis persisting in a broad zonal band from 5°N to 25°N.Since the western North Pacific subtropical hig
基金supported by the National Basic Research Program of China(2011CB403504 and 2011CB403505)
文摘Using a new global ocean reanalysis of the second generation Global Ocean Data Assimilation System of the Beijing Climate Center(BCC_GODAS2.0) spanning the period 1990-2009,we firstly quantify the accuracy of BCC_GODAS2.0 in representing the temperature and salinity by comparing with OISST and SODA data.The results show that the assimilation system may effectively improve the estimations of temperature and salinity by assimilating all kinds of observations,especially in the equatorial eastern Pacific.Moreover,the root mean square errors of monthly temperature and salinity are respectively reduced by 0.53℃ and 0.28 psu,compared with the model control simulation results.Then,the applicability of this ocean reanalysis for sea surface temperature(SST) anomaly variability in the tropical Pacific is evaluated with the observational HadISST data.The NINO3 index of the new reanalysis shows a good agreement with that of HadISST,with a correlation of 93.6%.Variations in SST from BCC_GODAS2.0 are similar to those obtained from HadISST data along the equator,showing the major large zonal-scale features such as the strong magnitude of seasonal cycle.The amplitude of SST anomaly standard deviation in the equatorial eastern Pacific is also closer to observations(HadISST) than NCEP GODAS does.Besides,the first two leading empirical orthogonal function(EOF) modes of the monthly SST anomalies over the tropical Pacific region are explored.The EOF1 pattern of BCC_GODAS2.0 captures a traditional El Ni o pattern,which improves magnitudes of the positive SST anomaly in the cold tongue of the eastern Pacific.The EOF2 pattern exhibits a El Ni o Modoki pattern.Comparatively,the EOF2 pattern of BCC_GODAS2.0 extends more strongly toward the subtropics.It also overcomes the problem that negative loadings are confined in the narrow equatorial eastern Pacific.Consequently,the magnitude and spatial distribution of the leading EOF patterns of BCC_GODAS2.0 are well consistent with those of HadISST.
基金supported by the National Basic Research Program of China (Grant No. 2010CB950400)the National Natural Science Foundation of China (Grant No. 41030961)the State Oceanic Administration of the People’s Republic of China
文摘Based on a linear model, the present study provides analytical solutions for ideal triple forcing sources similar to sea surface temperature anomaly （SSTA） pat- terns associated with El Nino-Southern Oscillation （ENSO） Modoki in winter. The ideal triple pattern is composed of an equatorially symmetric heat source in the middle and equatoriaUy asymmetric cold forcing in the southeast and northwest. The equatorially symmetric heat source excites low-level cyclonic circulation anomalies associated with Rossby waves in both hemispheres, while the northwest- ern and southeastern equatorially asymmetric cold sources induce low-level anomalous anticyclones associated with Rossby waves in the hemisphere where the forcing source is located. Low-level zonal winds converge toward the heat sources associated with Kelvin and Rossby waves. Due to unequal forcing intensity in the northwest and southeast, atmospheric responses around the equatorially symmetric forcing become asymmetric, and low-level cyclonic circulation anomalies in the Southern Hemisphere become greater than those in the Northern Hemisphere. Ascending （descending） flows coincide with heat （cold） sources, resulting in a double-cell structure over the regions of forcing sources. Ideal triple patterns similar to SSTA patterns associated with La Nina Modoki produce opposite atmospheric responses. The theoretical atmospheric responses are consistent with observed circulation anomalies associated with ENSO Modoki. Therefore, the theoretical solutions can explain the dynamics responsible for atmospheric circulation anomalies associated with ENSO Modoki events.
基金supported by the National Basic Research Program of china(973 Program)[grant number 2012c B957804]the External cooperation Program of BIc,chinese Academy of Sciences[grant number 134111KYSB20150016]
文摘Recent SST and atmospheric circulation anomaly data suggest that the 2015/16 El Nino event is quickly decaying. Some researchers have predicted a forthcoming La Nina event in late summer or early fall 2016. From the perspective of the modulation of tropical SST by solar activity, the authors studied the evolution of the 2015/16 El Nino event, which occurred right after the 2014 solar peak year. Based on statistical and composite analysis, a significant positive correlation was found between sunspot number index and El Ni^o Modoki index, with a lag of two years. A clear evolution of El Nino Modoki events was found within 1-3 years following each solar peak year during the past 126 years, suggesting that anomalously strong solar activity during solar peak periods favors the triggering of an El Nino Modoki event. The patterns of seasonal mean SST and wind anomalies since 2014 are more like a mixture of two types of El Nino （i.e. eastern Pacific El Nino and El Nino Modoki）, which is similar to the pattern modulated by solar activity during the years following a solar peak. Therefore, the El Nino Modoki component in the 2015/16 El Nino event may be a consequence of solar activity, which probably will not decay as quickly as the eastern Pacific El Nino component. The positive SST anomaly will probably sustain in the central equatorial Pacific （around the dateline） and the northeastern Pacific along the coast of North America, with a low-intensity level, during the second half of 2016.
基金Special Scientific Research Project for Public Welfare(201006021,201005019)Youth Foundation of Chinese State Oceanic Administration(2013257)+2 种基金Scientific Research Foundation of Third Institute of Oceanography,SOA(TIO2013002TIO2013003)National Special Project:Chinese Offshore Investigation and Assessment(908-02-01-02)
文摘El Nio Modoki,similar to but different from canonical El Nio,has been observed since the late1970s.In this paper,using HadISST and NCEP/NCAR wind data,we analyze the relationship between El Nio Modoki and Sea Surface Temperature(SST)in the offshore area of China and its adjacent waters for different seasons.Our results show a significant negative correlation between El Nio Modoki in summer and SST in autumn in the offshore area of China and its adjacent waters,particularly for regions located in the east of the Kuroshio.It is also found that during El Nio Modoki period,anomalous northerlies prevail over the regions from the northern part of the Philippines to the offshore area of China,indicating that the northerlies are unfavorable for the transport of warm water from the western tropical Pacific to the mid-latitude area.Consequently,El Nio Modoki in summer may play a substantial role in cold SST anomalies in the offshore area of China and its adjacent waters in autumn through the influence of the Kuroshio,with a lagged response of the ocean to the atmospheric wind field.
基金supported by the National Natural Science Foundation of China(41205048)the National Basic Research Program of China,"Structures,Variability and Climatic Impacts of Ocean Circulation and Warm Pool in the Tropical Pacific Ocean"(2012CB417403)the Special Project of Chinese Academy of Sciences(XDA11010401)
文摘A comparison of sensitivity in extratropical circulation in the Northern Hemisphere （NH） and Southern Hemisphere （SH） is conducted through observational analyses and diagnostic linear model experiments for two types of El Ni（n）o events,the traditional El Ni（n）o with the strongest warmth in the eastern tropical Pacific （EP El Ni（n）o） and the El Ni（n）o Modoki with the strongest warmth in the central tropical Pacific （CP El Ni（n）o）.It is shown that CP El Ni（n）o favors the occurrence of a negative-phase Northern Annular Mode （NAM）,while EP El Ni（n）o favors that of the Pacific-North American （PNA） pattern.In SH,both EP and CP El Ni（n）o induce a negative phase Southern Annular Mode （SAM）.However,the former has a greater amplitude,which is consistent with the stronger sea surface temperature （SST） warmth.The difference in the two types of El Ni（n）o events in NH may originate from the dependence of heating-induced extratropical response on the location of initial heating,which may be associated with activity of the stationary wave.In SH,the lack of sensitivity to the location of heating can be associated with weaker activity of the stationary wave therein.
