Based on normalized six-hourly black body temperature （TBB） data of three geostationary meteorological satellites,the leading modes of the mei-yu cloud system between 1998 and 2008 were extracted by the Empirical Or...Based on normalized six-hourly black body temperature （TBB） data of three geostationary meteorological satellites,the leading modes of the mei-yu cloud system between 1998 and 2008 were extracted by the Empirical Orthogonal Function （EOF） method,and the transition processes from the first typical leading mode to other leading modes were discussed and compared.The analysis shows that,when the southern mode （EOF1） transforms to the northeastern mode （EOF3）,in the mid-troposphere,a low trough develops and moves southeastward over central and eastern China.The circulation pattern is characterized by two highs and one low in the lower troposphere.A belt of low pressure is sandwiched between the weak high over central and western China and the strong western North Pacific subtropical high （WNPSH）.Cold air moves southward along the northerly flow behind the low,and meets the warm and moist air between the WNPSH and the forepart of the low trough,which leads to continuous convection.At the same time,the central extent of the WNPSH increases while its ridge extends westward.In addition,transitions from the southern mode to the dual centers mode and the tropical-low-influenced mode were found to be atypical,and so no common points could be concluded.Furthermore,the choice of threshold value can affect the number of samples discussed.展开更多
The first decadal leading mode of East Asian summer rainfall(EASR) is characterized by rainfall anomalies along the East Asian subtropical rain belt. This study focuses on the second decadal leading mode(2DLM), accoun...The first decadal leading mode of East Asian summer rainfall(EASR) is characterized by rainfall anomalies along the East Asian subtropical rain belt. This study focuses on the second decadal leading mode(2DLM), accounting for 17.3% of rainfall decadal variance, as distinct from the other two neighboring modes of EAMR, based on the state-of-the-art in-situ rainfall data.This mode is characterized by a South-China-wet–HuaiheRiver-dry pattern, and is dominated by a quasi-30-yr period. Further analysis reveals the 2DLM corresponds to an enhanced lower-level monsoon jet, an eastward extension of the western North Pacific subtropical high, and a weakened East Asian upper-level westerly jet flow. The Tibetan Plateau surface temperature and Pacific Decadal Oscillation(PDO) are closely linked with the 2DLM. The regressed SST pattern indicates the PDO-like pattern of sea surface temperature anomalies may have a teleconnection relationship with the 2DLM of EASR.展开更多
The Indian Ocean （IO） sea surface temperature （SST） was analyzed by using empirical orthogonal function （EOF）, and the leading mode of Indian Ocean （LMIO） SST was extracted. The major spatial and temporal char...The Indian Ocean （IO） sea surface temperature （SST） was analyzed by using empirical orthogonal function （EOF）, and the leading mode of Indian Ocean （LMIO） SST was extracted. The major spatial and temporal characters of LMIO were discussed, and the relationships between LMIO with Indian summer monsoon （ISM） and with China summer rainfalls （CSR） were investigated, then the impacts of LMIO on Asian summer monsoon （ASM） circulation were explored. Some notable results are obtained： The significant evolutional characters of LMIO are the consistent warming trend of almost the whole IO basin, the distinctive quasi-3- and quasi-ll-yr oscillations and remarkably interdecadal warming in 1976/1977 and 1997/1998, respectively. The LMIO impaired the lower level circulation of ISM and was closely related with the climate trend of CSR. It was associated with the weakening of South Asian high, the easterly winds south of the Tibetan Plateau, and the cross-equatorial flows over 10°-20°N, 40°-110°E at the upper level; with the strengthening of Somali cross-equatorial jet but the weakening of the circulation of ISM in the sector of India, the strengthening of south wind over the middle and lower reaches of Yangtze River and South China but the weakening of southwesterly winds over North China at lower level and with the increasing of surface pressure over the Asian Continent. Changes in the moisture flux transports integrated vertically over the whole troposphere associated with LMIO are similar to those in the lower level circulation. To sum up, the significant SST increasing trend of IO basin was one of the important causes for weakening of the ASM circulation and the southwards shifting of China summer rainband.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
By examining the second leading mode （EOF2） of the summer rainfall in China during 1958 2001 and associated circulations, the authors found that this prominent mode was a dipole pattern with rainfall decreasing to t...By examining the second leading mode （EOF2） of the summer rainfall in China during 1958 2001 and associated circulations, the authors found that this prominent mode was a dipole pattern with rainfall decreasing to the north of the Yangtze River and increasing to the south. This reverse relationship of the rainfalls to the north and to the south of the Yangtze River was related with the meridional circulations within East Asia and the neighboring region, excited by SST in the South China Sea-northwestern Pacific. When the SST was warmer, the geopotential heights at 500 hPa were positive in the low and high latitudes and negative in the middle latitudes. The anticyclone in the low latitudes favored the subtropical high over the northwestern Pacific （SHNP） shifting southwestward, leading to additional moisture transport over southern China. The anomalous atmospheric circulations along the East Asian coast tends to enhance upward movement over the region. Subsequently, rainfall in southern China is enhanced.展开更多
Atmospheric water vapor content(WVC)is a critical factor for East Asian winter precipitation.This study investigates the dominant modes of interannual variability in WVC over East Asia during winter and their underlyi...Atmospheric water vapor content(WVC)is a critical factor for East Asian winter precipitation.This study investigates the dominant modes of interannual variability in WVC over East Asia during winter and their underlying mechanisms.Based on the empirical orthogonal function(EOF)method,the leading mode(EOF1,R2=28.9%)of the interannual variability in the East Asian winter WVC exhibits a meridional dipole pattern characterized by opposite WVC anomalies over northeastern China and eastern China;the second mode(EOF2,R2=24.3%)of the interannual variability in the East Asian winter WVC exhibits a monopole pattern characterized by consistent WVC anomalies over eastern China.EOF1 is mainly modulated by two anomalous zonal water vapor transport(WVT)branches over northeastern China and eastern China,which are associated with an anomalous atmospheric wave train over Eurasia affected by sea ice cover in the Kara Sea-Barents Sea(SIC-KSBS)area in the preceding October-November(ON).EOF2 is mainly modulated by an anomalous westerly WVT branch over eastern China,which is associated with a circumglobal atmospheric zonal wave train in the Northern Hemisphere.This circumglobal zonal wave train is modulated by concurrent central and eastern tropical Pacific sea surface temperature anomalies.The SIC-KSBS anomalies in ON and the concurrent SST anomalies over tropical Pacific may partially account for the interannual variability of EOF1 and EOF2 winter WVC,and thus may provide a theoretical basis for improving the prediction of winter climate over East Asia.展开更多
This paper introduces the simulation, and controls using Simulink of MATLAB for PCTRAN (Personal Computer Transient Analysis) of the power control system (PWR) type pressurized water reactor of PWR WESTINGHOUSE AP1000...This paper introduces the simulation, and controls using Simulink of MATLAB for PCTRAN (Personal Computer Transient Analysis) of the power control system (PWR) type pressurized water reactor of PWR WESTINGHOUSE AP1000. The power controller model produces mathematical model description in nonlinear relation form in Simulink of MATLAB which is an important and popular program used at most universities for education. The power controller is described by a block diagram in this paper and some details introduce to clearly understand the work function. The results of action control compared with the PCTRAN programme in modes of automatic and manual control.展开更多
The present study investigates the interannual variation of June-November synoptic disturbance activity over the western North Pacific（WNP） and its relationship with large-scale circulation for the period 1958-2014....The present study investigates the interannual variation of June-November synoptic disturbance activity over the western North Pacific（WNP） and its relationship with large-scale circulation for the period 1958-2014. Two leading modes of eddy kinetic energy for the disturbance variability over the WNP are obtained by EOF analysis, characterized by anomalous eddy kinetic energy over the subtropical WNP and around the Philippines, respectively. These modes explain a large portion of the interannual variance of synoptic disturbance activity over the WNP. Both are associated with lower-level cyclonic anomalies, but with different locations： over the subtropical WNP for the first mode and over the South China Sea for the second mode. Considering the impact of ENSO on synoptic disturbance activity over the WNP, we repeat the analyses after removing the effect of ENSO, which is simply defined as the components linearly regressed onto the Ni o3.4 index, and find similar results, suggesting that the leading modes and their relationships with large-scale circulation exist without SST effects.Further analyses suggest that the meridional shear of zonal winds caused by cyclonic anomalies is crucial for maintaining the leading modes through barotropic conversion.展开更多
The North Pacific sea surface salinity(SSS)decadal variability(NPSDV)and its potential forcing were evaluated from 25 coupled models of the Coupled Model Intercomparison Project phase 6(CMIP6)considering the prospects...The North Pacific sea surface salinity(SSS)decadal variability(NPSDV)and its potential forcing were evaluated from 25 coupled models of the Coupled Model Intercomparison Project phase 6(CMIP6)considering the prospects for decadal climate predictions.The results indicated that the CMIP6 models generally reproduced the spatial patterns of NPSDV.The large standard deviation of the SSS anomaly over the strong current regions,such as the Kuroshio-Oyashio Extension(KOE),North Pacific Current(NPC),California Current System(CCS),and Alaskan Coastal Current(ACC),is reflected in the two leading modes of NPSDV:a dipole with out-of-phase loadings in the KOE-NPC versus CCS-ACC and a monopole with positive loading over the KOE-NPC.The order of modes is sensitive to individual models that exhibit discrepancies,especially in temporal phases and power spectra.An autoregressive model of order-1 was used to reconstruct the NPSDV with several forcing terms.The generally weaker influence of forcings in an autoregressive model of order-1 is partly related to the overestimated response time of NPSDV relative to forcings.Most NPSDV variances originate from the persistence of SSS anomalies,but the dominant forcing factors are diverse among models.The model diversity for the NPSDV simulation mainly arises from the influence of the tropical El Ni?o-Southern Oscillation through teleconnection on the North Pacific Oscillation or Aleutian Low with timescale dependence.Conversely,models that can reproduce the NPSDV well are not dependent on those with larger impacts from the North Pacific oceanic processes.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 40975023)the Special Promotion Program for Meteorology (Grant No. GYHY201406011 and No. GYHY201106044)the National High Technology Research and Development Project of China (Grant No. 2012AA120903)
文摘Based on normalized six-hourly black body temperature （TBB） data of three geostationary meteorological satellites,the leading modes of the mei-yu cloud system between 1998 and 2008 were extracted by the Empirical Orthogonal Function （EOF） method,and the transition processes from the first typical leading mode to other leading modes were discussed and compared.The analysis shows that,when the southern mode （EOF1） transforms to the northeastern mode （EOF3）,in the mid-troposphere,a low trough develops and moves southeastward over central and eastern China.The circulation pattern is characterized by two highs and one low in the lower troposphere.A belt of low pressure is sandwiched between the weak high over central and western China and the strong western North Pacific subtropical high （WNPSH）.Cold air moves southward along the northerly flow behind the low,and meets the warm and moist air between the WNPSH and the forepart of the low trough,which leads to continuous convection.At the same time,the central extent of the WNPSH increases while its ridge extends westward.In addition,transitions from the southern mode to the dual centers mode and the tropical-low-influenced mode were found to be atypical,and so no common points could be concluded.Furthermore,the choice of threshold value can affect the number of samples discussed.
基金supported by the National Basic Research Program (973 Program, Grant No. 2012CB417203)the R&D Special Fund for Public Welfare Industry (Meteorology) (Grant No. GYHY201406001)+1 种基金Strategic Leading Science Projects of the Chinese Academy of Sciences (Grant No. XDA11010402)the National National Science Foundation of China (Grant Nos. 91337110 and 40805038)
文摘The first decadal leading mode of East Asian summer rainfall(EASR) is characterized by rainfall anomalies along the East Asian subtropical rain belt. This study focuses on the second decadal leading mode(2DLM), accounting for 17.3% of rainfall decadal variance, as distinct from the other two neighboring modes of EAMR, based on the state-of-the-art in-situ rainfall data.This mode is characterized by a South-China-wet–HuaiheRiver-dry pattern, and is dominated by a quasi-30-yr period. Further analysis reveals the 2DLM corresponds to an enhanced lower-level monsoon jet, an eastward extension of the western North Pacific subtropical high, and a weakened East Asian upper-level westerly jet flow. The Tibetan Plateau surface temperature and Pacific Decadal Oscillation(PDO) are closely linked with the 2DLM. The regressed SST pattern indicates the PDO-like pattern of sea surface temperature anomalies may have a teleconnection relationship with the 2DLM of EASR.
基金the National Basic Key Research Program(973)under Grant Nos.2006CB403604 and 2006CB403606the National Natural Science Foundation of China under Grant No.40705033
文摘The Indian Ocean （IO） sea surface temperature （SST） was analyzed by using empirical orthogonal function （EOF）, and the leading mode of Indian Ocean （LMIO） SST was extracted. The major spatial and temporal characters of LMIO were discussed, and the relationships between LMIO with Indian summer monsoon （ISM） and with China summer rainfalls （CSR） were investigated, then the impacts of LMIO on Asian summer monsoon （ASM） circulation were explored. Some notable results are obtained： The significant evolutional characters of LMIO are the consistent warming trend of almost the whole IO basin, the distinctive quasi-3- and quasi-ll-yr oscillations and remarkably interdecadal warming in 1976/1977 and 1997/1998, respectively. The LMIO impaired the lower level circulation of ISM and was closely related with the climate trend of CSR. It was associated with the weakening of South Asian high, the easterly winds south of the Tibetan Plateau, and the cross-equatorial flows over 10°-20°N, 40°-110°E at the upper level; with the strengthening of Somali cross-equatorial jet but the weakening of the circulation of ISM in the sector of India, the strengthening of south wind over the middle and lower reaches of Yangtze River and South China but the weakening of southwesterly winds over North China at lower level and with the increasing of surface pressure over the Asian Continent. Changes in the moisture flux transports integrated vertically over the whole troposphere associated with LMIO are similar to those in the lower level circulation. To sum up, the significant SST increasing trend of IO basin was one of the important causes for weakening of the ASM circulation and the southwards shifting of China summer rainband.
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.
基金supported by the National Basic Research Program of China(Grant Nos 2004CB418302 and 2009CB421404)Na-tional Natural Science Foundation of China (Grant No40675058)
文摘By examining the second leading mode （EOF2） of the summer rainfall in China during 1958 2001 and associated circulations, the authors found that this prominent mode was a dipole pattern with rainfall decreasing to the north of the Yangtze River and increasing to the south. This reverse relationship of the rainfalls to the north and to the south of the Yangtze River was related with the meridional circulations within East Asia and the neighboring region, excited by SST in the South China Sea-northwestern Pacific. When the SST was warmer, the geopotential heights at 500 hPa were positive in the low and high latitudes and negative in the middle latitudes. The anticyclone in the low latitudes favored the subtropical high over the northwestern Pacific （SHNP） shifting southwestward, leading to additional moisture transport over southern China. The anomalous atmospheric circulations along the East Asian coast tends to enhance upward movement over the region. Subsequently, rainfall in southern China is enhanced.
基金This study was funded by the Natural Sci-ence Foundation of China(Grant Nos.41991283 and 41805047)the Natural Science Foundation of Jiangsu Province of China(Grant No.BK20180807).
文摘Atmospheric water vapor content(WVC)is a critical factor for East Asian winter precipitation.This study investigates the dominant modes of interannual variability in WVC over East Asia during winter and their underlying mechanisms.Based on the empirical orthogonal function(EOF)method,the leading mode(EOF1,R2=28.9%)of the interannual variability in the East Asian winter WVC exhibits a meridional dipole pattern characterized by opposite WVC anomalies over northeastern China and eastern China;the second mode(EOF2,R2=24.3%)of the interannual variability in the East Asian winter WVC exhibits a monopole pattern characterized by consistent WVC anomalies over eastern China.EOF1 is mainly modulated by two anomalous zonal water vapor transport(WVT)branches over northeastern China and eastern China,which are associated with an anomalous atmospheric wave train over Eurasia affected by sea ice cover in the Kara Sea-Barents Sea(SIC-KSBS)area in the preceding October-November(ON).EOF2 is mainly modulated by an anomalous westerly WVT branch over eastern China,which is associated with a circumglobal atmospheric zonal wave train in the Northern Hemisphere.This circumglobal zonal wave train is modulated by concurrent central and eastern tropical Pacific sea surface temperature anomalies.The SIC-KSBS anomalies in ON and the concurrent SST anomalies over tropical Pacific may partially account for the interannual variability of EOF1 and EOF2 winter WVC,and thus may provide a theoretical basis for improving the prediction of winter climate over East Asia.
文摘This paper introduces the simulation, and controls using Simulink of MATLAB for PCTRAN (Personal Computer Transient Analysis) of the power control system (PWR) type pressurized water reactor of PWR WESTINGHOUSE AP1000. The power controller model produces mathematical model description in nonlinear relation form in Simulink of MATLAB which is an important and popular program used at most universities for education. The power controller is described by a block diagram in this paper and some details introduce to clearly understand the work function. The results of action control compared with the PCTRAN programme in modes of automatic and manual control.
基金supported by the National Natural Science Foundation of China (Grant Nos.41320104007,41475074 and 41475077)
文摘The present study investigates the interannual variation of June-November synoptic disturbance activity over the western North Pacific（WNP） and its relationship with large-scale circulation for the period 1958-2014. Two leading modes of eddy kinetic energy for the disturbance variability over the WNP are obtained by EOF analysis, characterized by anomalous eddy kinetic energy over the subtropical WNP and around the Philippines, respectively. These modes explain a large portion of the interannual variance of synoptic disturbance activity over the WNP. Both are associated with lower-level cyclonic anomalies, but with different locations： over the subtropical WNP for the first mode and over the South China Sea for the second mode. Considering the impact of ENSO on synoptic disturbance activity over the WNP, we repeat the analyses after removing the effect of ENSO, which is simply defined as the components linearly regressed onto the Ni o3.4 index, and find similar results, suggesting that the leading modes and their relationships with large-scale circulation exist without SST effects.Further analyses suggest that the meridional shear of zonal winds caused by cyclonic anomalies is crucial for maintaining the leading modes through barotropic conversion.
基金supported by the National Key Research and Development Program(Grant No.2020YFA0608902)the National Natural Sciences Foundation of China(Grant Nos.41976026,41931183,41706021&41976188)。
文摘The North Pacific sea surface salinity(SSS)decadal variability(NPSDV)and its potential forcing were evaluated from 25 coupled models of the Coupled Model Intercomparison Project phase 6(CMIP6)considering the prospects for decadal climate predictions.The results indicated that the CMIP6 models generally reproduced the spatial patterns of NPSDV.The large standard deviation of the SSS anomaly over the strong current regions,such as the Kuroshio-Oyashio Extension(KOE),North Pacific Current(NPC),California Current System(CCS),and Alaskan Coastal Current(ACC),is reflected in the two leading modes of NPSDV:a dipole with out-of-phase loadings in the KOE-NPC versus CCS-ACC and a monopole with positive loading over the KOE-NPC.The order of modes is sensitive to individual models that exhibit discrepancies,especially in temporal phases and power spectra.An autoregressive model of order-1 was used to reconstruct the NPSDV with several forcing terms.The generally weaker influence of forcings in an autoregressive model of order-1 is partly related to the overestimated response time of NPSDV relative to forcings.Most NPSDV variances originate from the persistence of SSS anomalies,but the dominant forcing factors are diverse among models.The model diversity for the NPSDV simulation mainly arises from the influence of the tropical El Ni?o-Southern Oscillation through teleconnection on the North Pacific Oscillation or Aleutian Low with timescale dependence.Conversely,models that can reproduce the NPSDV well are not dependent on those with larger impacts from the North Pacific oceanic processes.
