The magnitude of El Nino determines the level of its global impact.Yet,how well our state-of-the-art models simulate this key aspect of El Nino is not well documented.Previous studies tend to ignore El Nino-Southern O...The magnitude of El Nino determines the level of its global impact.Yet,how well our state-of-the-art models simulate this key aspect of El Nino is not well documented.Previous studies tend to ignore El Nino-Southern Oscillation(ENSO)asymmetry and equate the variance of ENSO to the magnitude of El Nino.Moreover,previous evaluations are more focused on the surface manifestation of El Nino.Here,we quantify the magnitudes of El Nino and La Nina separately,both at the surface and subsurface levels.At the surface,we find that while the magnitude of La Nina events in most models is generally stronger than observed,the magnitude of El Nino is more diverse to observations.In fact,in many models,El Nino is weaker than observed.This bias in the magnitude of El Nino is more pronounced in the subsurface.We attribute this weakness in the subsurface to the generally weaker coupling strength and the apparent stronger ENSO at the surface to a lack of sufficiently strong negative feedback from the surface heat flux in the models.When normalized by the variance of ENSO,the lack of exceptionally strong El Nino events in the models is more common and pronounced.We further studied the lifespan of El Nino and La Nina events and have found that multi-year duration is not confined to just La Nina events.There are also El Nino events that last more than one year.Moreover,we have found that multi-year long La Nina events tend to occur over the decades with strong El Nino events.The study also briefly explores the impact of global warming on the duration of ENSO events through the use of a simple model and simulations by CMIP6 models.It has been found that the frequency of multi-year El Nino and La Nina events increases with global warming.展开更多
Leucogranite,pegmatite,and aplite from selected areas in the Wadi El Gemal area in the southern Eastern Desert of Egypt were investigated geochemically for their petrogenesis.These rocks represent a significant episod...Leucogranite,pegmatite,and aplite from selected areas in the Wadi El Gemal area in the southern Eastern Desert of Egypt were investigated geochemically for their petrogenesis.These rocks represent a significant episode of felsic magmatism during the late stage of the Pan-African orogeny in the evolution of the Arabian–Nubian Shield(ANS)during the Late Neoproterozoic.On a petrographic basis,the leucogranite is sometimes garnetiferous and can be distinguished into monzogranite,syenogranite,and alkali feldspar granite.The analyses of muscovite,biotite,garnet,and apatite reveal the magmatic nature of the studied leucogranite.The investigated leucogranite,pegmatite,and aplite are alkali-calcic,calc-alkaline,and peraluminous.The peraluminous nature of these rocks is evidenced by using the chemical analyses of biotite.These studied rocks show a slight enrichment in light rare-earth elements(LREEs)and large-ion lithophile elements(LILE,especially Rb and Th),with an insignificant depletion of heavy rareearth elements(HREEs).On a geochemical basis,the leucogranite,pegmatite,and aplite in the study area crystallized from multiple-sourced melts that include mafic,metagraywake,and pelitic.They were derived from melts generated at crystallization temperatures around 568-900℃ for leucogranite,553-781℃ for pegmatite,and 639-779℃ for aplite based on the Zr saturation geothermometers,and at a pressure around 0.39-0.48 GPa,i.e.shallow depth intrusions.The studied felsic rocks have strong negative Eu anomalies,which are very consistent with an upper crust composition,indicating fractionation of feldspar cumulates.Also,they show a moderate La/Sm ratio indicating combined magmatic processes represented by partial melting and fractional crystallization.Integration of whole-rock chemical composition and mineral microanalysis suggests that felsic magmatism in the west Wadi El Gemal area produced voluminous masses of syn-to post-collisional granite,pegmatite,and aplite.An evolutionary three-stage model is presented to understand late magmatism in the ANS in terms of a geodynamic model.Such a model discusses the propagation of felsic magmatism in the ANS during syn-collisional to post-collisional stages.展开更多
In the south Eastern Desert of Egypt,two contrasting types of magmatism(mafic and felsic) are recorded in the Wadi Kalalat area,and form the Gabal El Motaghiarat and Gabal Batuga intrusions,respectively.The two intrus...In the south Eastern Desert of Egypt,two contrasting types of magmatism(mafic and felsic) are recorded in the Wadi Kalalat area,and form the Gabal El Motaghiarat and Gabal Batuga intrusions,respectively.The two intrusions post-dates ophiolitic and arc associations represented by serpentinite and metagabbro-diorite,respectively.The mafic intrusion has a basal ultramafic member represented by fresh peridotite,which is followed upward by olivine gabbro and anorthositic or leucogabbro.This mafic intrusion pertains to the Alaskan-type mafic-ultramafic intrusions in the Arabian-Nubian Shield(ANS)being of tholeiitic nature and emplaced in a typical arc setting.On the other hand,the Gabal Batuga intrusion comprises three varieties of fresh A-type granites of high K-calc alkaline nature,which is peraluminous and garnetbearing in parts.A narrow thermal aureole in the olivine gabbro of the mafic intrusion was developed due to the intrusion of the Batuga granites.This results in the development of a hornfelsic melagabbro variety in which the composition changed from tholeiitic to a calc-alkaline composition due to the addition of S_(i)O_(2),Al_(2)O_(3),alkalis,lithosphile elements(LILEs) such as Rb(70 ppm) and Y(28 ppm) from the felsic intrusion.Outside the thermal aureole,Rb amounts 2-8 ppm and Y lies in the range <2-6ppm.It is believed that the Gabal Batuga felsic intrusion started to emplace during the waning stage of an arc system,with transition from the pre-collisional(i.e.,arc setting) to post-collisional and within plate settings.Magma from which the Gabal Batuga granites were fractionated is high-K calc-alkaline giving rise to a typical post-collisional A-type granite(A_(2)-subtype) indicating an origin from an underplating crustal source.Accordingly,it is stressed here that the younger granites in the ANS are not exclusively post-collisional and within-plate but most likely they started to develop before closure of the arc system.The possible source(s) of mafic magmas that resulted in the formation of the two intrusions are discussed.Mineralogical and geochemical data of the post-intrusion dykes(mafic and felsic) suggest typical active continental rift/within-plate settings.展开更多
The subtropical North and South Pacific Meridional Modes(NPMM and SPMM)are well known precursors of El Niño-Southern Oscillation(ENSO).However,relationship between them is not constant.In the early 1980,the relat...The subtropical North and South Pacific Meridional Modes(NPMM and SPMM)are well known precursors of El Niño-Southern Oscillation(ENSO).However,relationship between them is not constant.In the early 1980,the relationship experienced an interdecadal transition.Changes in this connection can be attributed mainly to the phase change of the Pacific decadal oscillation(PDO).During the positive phase of PDO,a shallower thermocline in the central Pacific is responsible for the stronger trade wind charging(TWC)mechanism,which leads to a stronger equatorial subsurface temperature evolution.This dynamic process strengthens the connection between NPMM and ENSO.Associated with the negative phase of PDO,a shallower thermocline over southeastern Pacific allows an enhanced wind-evaporation-SST(WES)feedback,strengthening the connection between SPMM and ENSO.Using 35 Coupled Model Intercomparison Project Phase 6(CMIP6)models,we examined the NPMM/SPMM performance and its connection with ENSO in the historical runs.The great majority of CMIP6 models can reproduce the pattern of NPMM and SPMM well,but they reveal discrepant ENSO and NPMM/SPMM relationship.The intermodal uncertainty for the connection of NPMM-ENSO is due to different TWC mechanism.A stronger TWC mechanism will enhance NPMM forcing.For SPMM,few models can simulate a good relationship with ENSO.The intermodel spread in the relationship of SPMM and ENSO owing to SST bias in the southeastern Pacific,as WES feedback is stronger when the southeastern Pacific is warmer.展开更多
The dynamical prediction of the Asian-Australian monsoon(AAM)has been an important and long-standing issue in climate science.In this study,the predictability of the first two leading modes of the AAM is studied using...The dynamical prediction of the Asian-Australian monsoon(AAM)has been an important and long-standing issue in climate science.In this study,the predictability of the first two leading modes of the AAM is studied using retrospective prediction datasets from the seasonal forecasting models in four operational centers worldwide.Results show that the model predictability of the leading AAM modes is sensitive to how they are defined in different seasonal sequences,especially for the second mode.The first AAM mode,from various seasonal sequences,coincides with the El Niño phase transition in the eastern-central Pacific.The second mode,initialized from boreal summer and autumn,leads El Niño by about one year but can exist during the decay phase of El Niño when initialized from boreal winter and spring.Our findings hint that ENSO,as an early signal,is conducive to better performance of model predictions in capturing the spatiotemporal variations of the leading AAM modes.Still,the persistence barrier of ENSO in spring leads to poor forecasting skills of spatial features.The multimodel ensemble(MME)mean shows some advantage in capturing the spatiotemporal variations of the AAM modes but does not provide a significant improvement in predicting its temporal features compared to the best individual models in predicting its temporal features.The BCC_CSM1.1M shows promising skill in predicting the two AAM indices associated with two leading AAM modes.The predictability demonstrated in this study is potentially useful for AAM prediction in operational and climate services.展开更多
-In this paper, monthly mean SST data in a large area are used. After the spacial average of the data is carried out and the secular monthly means are substracted, a time series (Jan. 1951-Dec. 1985) of SST anomalies ...-In this paper, monthly mean SST data in a large area are used. After the spacial average of the data is carried out and the secular monthly means are substracted, a time series (Jan. 1951-Dec. 1985) of SST anomalies of the cold tongue water area in the eastern tropical Pacific Ocean is obtained. On the basis of the time series, an autoregression model, a self-exciting threshold autoregression model and an open loop autoregression model are developed respectively. The interannual variations are simulated by means of those models. The simulation results show that all the three models have made very good hindcasting for the nine El Nino events since 1951. In order to test the reliability of the open loop threshold model, extrapolated forecast was made for the period of Jan. 1986-Feb. 1987. It can be seen from the forecasting that the model could forecast well the beginning and strengthening stages of the recent El Nino event (1986-1987). Correlation coefficients of the estimations to observations are respectively 0. 84, 0. 88 and 0. 89. It is obvious that all the models work well and the open loop threshold one is the best. So the open loop threshold autoregression model is a useful tool for monitoring the SSTinterannual variation of the cold tongue water area in the Eastern Equatorial Pacific Ocean and for estimating the El Nino strength.展开更多
近日,IBM京召开了主题为"大数据危机大整合出击"——IBM ELS大数据策略媒体发布会,阐述ELS在大数据时代的全新策略,旨在帮助企业用户抓住大数据带来的机遇,应对大数据给基础架构带来的压力和挑战。基于主机架构的企业级Linux...近日,IBM京召开了主题为"大数据危机大整合出击"——IBM ELS大数据策略媒体发布会,阐述ELS在大数据时代的全新策略,旨在帮助企业用户抓住大数据带来的机遇,应对大数据给基础架构带来的压力和挑战。基于主机架构的企业级Linux服务器(Enterprise Linux Server)。展开更多
基金The National Natural Science Foundation of China under contract No.42250710154。
文摘The magnitude of El Nino determines the level of its global impact.Yet,how well our state-of-the-art models simulate this key aspect of El Nino is not well documented.Previous studies tend to ignore El Nino-Southern Oscillation(ENSO)asymmetry and equate the variance of ENSO to the magnitude of El Nino.Moreover,previous evaluations are more focused on the surface manifestation of El Nino.Here,we quantify the magnitudes of El Nino and La Nina separately,both at the surface and subsurface levels.At the surface,we find that while the magnitude of La Nina events in most models is generally stronger than observed,the magnitude of El Nino is more diverse to observations.In fact,in many models,El Nino is weaker than observed.This bias in the magnitude of El Nino is more pronounced in the subsurface.We attribute this weakness in the subsurface to the generally weaker coupling strength and the apparent stronger ENSO at the surface to a lack of sufficiently strong negative feedback from the surface heat flux in the models.When normalized by the variance of ENSO,the lack of exceptionally strong El Nino events in the models is more common and pronounced.We further studied the lifespan of El Nino and La Nina events and have found that multi-year duration is not confined to just La Nina events.There are also El Nino events that last more than one year.Moreover,we have found that multi-year long La Nina events tend to occur over the decades with strong El Nino events.The study also briefly explores the impact of global warming on the duration of ENSO events through the use of a simple model and simulations by CMIP6 models.It has been found that the frequency of multi-year El Nino and La Nina events increases with global warming.
基金finational supported by the Foundation of Science,Technology and Innovation Funding Authority(STDF)(Award Number:47106Recipient:Mokhles K K.Azer)。
文摘Leucogranite,pegmatite,and aplite from selected areas in the Wadi El Gemal area in the southern Eastern Desert of Egypt were investigated geochemically for their petrogenesis.These rocks represent a significant episode of felsic magmatism during the late stage of the Pan-African orogeny in the evolution of the Arabian–Nubian Shield(ANS)during the Late Neoproterozoic.On a petrographic basis,the leucogranite is sometimes garnetiferous and can be distinguished into monzogranite,syenogranite,and alkali feldspar granite.The analyses of muscovite,biotite,garnet,and apatite reveal the magmatic nature of the studied leucogranite.The investigated leucogranite,pegmatite,and aplite are alkali-calcic,calc-alkaline,and peraluminous.The peraluminous nature of these rocks is evidenced by using the chemical analyses of biotite.These studied rocks show a slight enrichment in light rare-earth elements(LREEs)and large-ion lithophile elements(LILE,especially Rb and Th),with an insignificant depletion of heavy rareearth elements(HREEs).On a geochemical basis,the leucogranite,pegmatite,and aplite in the study area crystallized from multiple-sourced melts that include mafic,metagraywake,and pelitic.They were derived from melts generated at crystallization temperatures around 568-900℃ for leucogranite,553-781℃ for pegmatite,and 639-779℃ for aplite based on the Zr saturation geothermometers,and at a pressure around 0.39-0.48 GPa,i.e.shallow depth intrusions.The studied felsic rocks have strong negative Eu anomalies,which are very consistent with an upper crust composition,indicating fractionation of feldspar cumulates.Also,they show a moderate La/Sm ratio indicating combined magmatic processes represented by partial melting and fractional crystallization.Integration of whole-rock chemical composition and mineral microanalysis suggests that felsic magmatism in the west Wadi El Gemal area produced voluminous masses of syn-to post-collisional granite,pegmatite,and aplite.An evolutionary three-stage model is presented to understand late magmatism in the ANS in terms of a geodynamic model.Such a model discusses the propagation of felsic magmatism in the ANS during syn-collisional to post-collisional stages.
文摘In the south Eastern Desert of Egypt,two contrasting types of magmatism(mafic and felsic) are recorded in the Wadi Kalalat area,and form the Gabal El Motaghiarat and Gabal Batuga intrusions,respectively.The two intrusions post-dates ophiolitic and arc associations represented by serpentinite and metagabbro-diorite,respectively.The mafic intrusion has a basal ultramafic member represented by fresh peridotite,which is followed upward by olivine gabbro and anorthositic or leucogabbro.This mafic intrusion pertains to the Alaskan-type mafic-ultramafic intrusions in the Arabian-Nubian Shield(ANS)being of tholeiitic nature and emplaced in a typical arc setting.On the other hand,the Gabal Batuga intrusion comprises three varieties of fresh A-type granites of high K-calc alkaline nature,which is peraluminous and garnetbearing in parts.A narrow thermal aureole in the olivine gabbro of the mafic intrusion was developed due to the intrusion of the Batuga granites.This results in the development of a hornfelsic melagabbro variety in which the composition changed from tholeiitic to a calc-alkaline composition due to the addition of S_(i)O_(2),Al_(2)O_(3),alkalis,lithosphile elements(LILEs) such as Rb(70 ppm) and Y(28 ppm) from the felsic intrusion.Outside the thermal aureole,Rb amounts 2-8 ppm and Y lies in the range <2-6ppm.It is believed that the Gabal Batuga felsic intrusion started to emplace during the waning stage of an arc system,with transition from the pre-collisional(i.e.,arc setting) to post-collisional and within plate settings.Magma from which the Gabal Batuga granites were fractionated is high-K calc-alkaline giving rise to a typical post-collisional A-type granite(A_(2)-subtype) indicating an origin from an underplating crustal source.Accordingly,it is stressed here that the younger granites in the ANS are not exclusively post-collisional and within-plate but most likely they started to develop before closure of the arc system.The possible source(s) of mafic magmas that resulted in the formation of the two intrusions are discussed.Mineralogical and geochemical data of the post-intrusion dykes(mafic and felsic) suggest typical active continental rift/within-plate settings.
基金Supported by the National Natural Science Foundation of China(NSFC)(No.41976027)。
文摘The subtropical North and South Pacific Meridional Modes(NPMM and SPMM)are well known precursors of El Niño-Southern Oscillation(ENSO).However,relationship between them is not constant.In the early 1980,the relationship experienced an interdecadal transition.Changes in this connection can be attributed mainly to the phase change of the Pacific decadal oscillation(PDO).During the positive phase of PDO,a shallower thermocline in the central Pacific is responsible for the stronger trade wind charging(TWC)mechanism,which leads to a stronger equatorial subsurface temperature evolution.This dynamic process strengthens the connection between NPMM and ENSO.Associated with the negative phase of PDO,a shallower thermocline over southeastern Pacific allows an enhanced wind-evaporation-SST(WES)feedback,strengthening the connection between SPMM and ENSO.Using 35 Coupled Model Intercomparison Project Phase 6(CMIP6)models,we examined the NPMM/SPMM performance and its connection with ENSO in the historical runs.The great majority of CMIP6 models can reproduce the pattern of NPMM and SPMM well,but they reveal discrepant ENSO and NPMM/SPMM relationship.The intermodal uncertainty for the connection of NPMM-ENSO is due to different TWC mechanism.A stronger TWC mechanism will enhance NPMM forcing.For SPMM,few models can simulate a good relationship with ENSO.The intermodel spread in the relationship of SPMM and ENSO owing to SST bias in the southeastern Pacific,as WES feedback is stronger when the southeastern Pacific is warmer.
基金supported by the National Natural Science Foundation of China(Grant Nos.U2242206,41975094 and 41905062)the National Key Research and Development Program on monitoring,Early Warning and Prevention of Major Natural Disaster(Grant Nos.2017YFC1502302 and 2018YFC1506005)+1 种基金the Basic Research and Operational Special Project of CAMS(Grant No.2021Z007)the Met Office Climate Science for Service Partnership(CSSP)China.
文摘The dynamical prediction of the Asian-Australian monsoon(AAM)has been an important and long-standing issue in climate science.In this study,the predictability of the first two leading modes of the AAM is studied using retrospective prediction datasets from the seasonal forecasting models in four operational centers worldwide.Results show that the model predictability of the leading AAM modes is sensitive to how they are defined in different seasonal sequences,especially for the second mode.The first AAM mode,from various seasonal sequences,coincides with the El Niño phase transition in the eastern-central Pacific.The second mode,initialized from boreal summer and autumn,leads El Niño by about one year but can exist during the decay phase of El Niño when initialized from boreal winter and spring.Our findings hint that ENSO,as an early signal,is conducive to better performance of model predictions in capturing the spatiotemporal variations of the leading AAM modes.Still,the persistence barrier of ENSO in spring leads to poor forecasting skills of spatial features.The multimodel ensemble(MME)mean shows some advantage in capturing the spatiotemporal variations of the AAM modes but does not provide a significant improvement in predicting its temporal features compared to the best individual models in predicting its temporal features.The BCC_CSM1.1M shows promising skill in predicting the two AAM indices associated with two leading AAM modes.The predictability demonstrated in this study is potentially useful for AAM prediction in operational and climate services.
文摘-In this paper, monthly mean SST data in a large area are used. After the spacial average of the data is carried out and the secular monthly means are substracted, a time series (Jan. 1951-Dec. 1985) of SST anomalies of the cold tongue water area in the eastern tropical Pacific Ocean is obtained. On the basis of the time series, an autoregression model, a self-exciting threshold autoregression model and an open loop autoregression model are developed respectively. The interannual variations are simulated by means of those models. The simulation results show that all the three models have made very good hindcasting for the nine El Nino events since 1951. In order to test the reliability of the open loop threshold model, extrapolated forecast was made for the period of Jan. 1986-Feb. 1987. It can be seen from the forecasting that the model could forecast well the beginning and strengthening stages of the recent El Nino event (1986-1987). Correlation coefficients of the estimations to observations are respectively 0. 84, 0. 88 and 0. 89. It is obvious that all the models work well and the open loop threshold one is the best. So the open loop threshold autoregression model is a useful tool for monitoring the SSTinterannual variation of the cold tongue water area in the Eastern Equatorial Pacific Ocean and for estimating the El Nino strength.
