基于贝叶斯模式平均方法(Bayesian Model Averaging),发展了一个NINO3.4指数的多模式客观权重集合预报方法(简称OBJ)。该方法基于训练期内单个模式的预报结果,用线性回归订正单个预报的偏差,依据模式的预报效果估计单个模式的权重。利用...基于贝叶斯模式平均方法(Bayesian Model Averaging),发展了一个NINO3.4指数的多模式客观权重集合预报方法(简称OBJ)。该方法基于训练期内单个模式的预报结果,用线性回归订正单个预报的偏差,依据模式的预报效果估计单个模式的权重。利用2002年2月—2015年10月美国哥伦比亚大学国际气候与社会研究所(IRI)提供的7个单一模式对NINO3.4指数的预报结果进行OBJ试验,并采用均方根误差对多模式集合平均预报(简称ENS)和OBJ的预报结果进行检验和评估。结果表明,ENS的预报效果优于7个单一模式的预报效果,而OBJ预报效果优于ENS预报效果,其NINO3.4指数的均方根误差比ENS方法降低了4%。将单一模式预报结果按时间划分为训练期和预报期,利用独立样本估计OBJ的参数并进行预报试验,这些试验也表明,OBJ能进一步提高预报精度。展开更多
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 Walker circulation(WC)has always been an important issue in atmospheric science research due to the association between the WC and tropical Pacific sea surface temperature(SST),and between the WC and ENSO events.I...The Walker circulation(WC)has always been an important issue in atmospheric science research due to the association between the WC and tropical Pacific sea surface temperature(SST),and between the WC and ENSO events.In this paper,a new index-Omega index(OMGI)-is constructed for WC characterization based on the NCEP/NCAR reanalysis data of monthly mean vertical velocity in recent 70 years(1948-2017).Results show that the OMGI can accurately depict the variation characteristics of WC on seasonal,annual and decadal time-scales.There is a significant inverse correlation between the OMGI and equatorial eastern and central Pacific SST.Meanwhile,the peak of the OMGI appears ahead of the ENSO peak,and therefore is able to reflect the SST in the equatorial Pacific.Especially,in 35 ENSO events,the peak of the OMGI appears earlier than Ni?o 3.4 index for 19 times with 2.6 months ahead on average.In 16 El Ni?o events,the peak of the OMGI occurs ahead of the El Ni?o for 9 times with 4 months ahead on average.In19 La Ni?a events,the OMGI peak arises 10 times earlier than the La Ni?a peak,with an average of 1.4 months ahead.OMGI shows obvious leading effect and stability over ENSO events with different strengths and types of single peak and multi peaks:the peak of the OMGI keeps about 2-3 months ahead of the ENSO.Compared with other WC indexes such as UWI and SPLI,OMGI has some advantages in the ability to describe WC changes and present the probability and the time of prediction of ENSO event peaks.展开更多
Abnormal weather conditions and extreme weather existed over the Kingdom Saudi Arabia (KSA) through the last decades. The present paper investigates the relationship between the Oceanic Nino Index (ONI) and variabilit...Abnormal weather conditions and extreme weather existed over the Kingdom Saudi Arabia (KSA) through the last decades. The present paper investigates the relationship between the Oceanic Nino Index (ONI) and variability of surface air temperature and precipitation rate over KSA through the period from 1950 to 2015 year. The NCEP/NCAR Reanalysis of monthly data sets of the mean surface air temperature and precipitation rate for the domain of the KSA is used. In addition, El Nino3.4 monthly data through the period (1950-2015) are used. For that period, the data set of the three months moving average of Nino3.4 anomaly, Oceanic Nino index (ONI), is used and analyzed. The time series, anomaly and correlation coefficient techniques are used to analyze the data sets through the present study. The results revealed that the KSA climate parameters, temperature and precipitation rates are controlled by ONI mainly in the autumn and winter seasons.展开更多
By analyzing the variability of global SST(sea surface temperature) anomalies,we propose a unified Ni o index using the surface thermal centroid anomaly of the region along the Pacific equator embraced by the 0.7°...By analyzing the variability of global SST(sea surface temperature) anomalies,we propose a unified Ni o index using the surface thermal centroid anomaly of the region along the Pacific equator embraced by the 0.7°C contour line of the standard deviation of the SST anomalies and try to unify the traditional Ni o regions into a single entity.The unified Ni o region covers almost all of the traditional Ni o regions.The anomaly time series of the averaged SST over this region are closely correlated to historical Ni o indices.The anomaly time series of the zonal and meridional thermal centroid have close correlation with historical TNI(Trans-Ni o index) indices,showing differences among El Ni o(La Ni a) events.The meridional centroid anomaly suggests that areas of maximum temperature anomaly are moving meridionally(although slightly) with synchronous zonal movement.The zonal centroid anomalies of the unified Ni o region are found helpful in the classification of the Eastern Pacific(EP)/Central Pacific(CP) types of El Ni o events.More importantly,the zonal centroid anomaly shows that warm areas might move during a single warming/cooling phase.All the current Ni o indices can be well represented by a simple linear combination of unified Ni o indices,which suggests that the thermal anomaly(SSTA) and thermal centroid location anomaly of the unified Ni o region would yield a more complete image of each El Ni o/ La Ni a event.展开更多
文摘基于贝叶斯模式平均方法(Bayesian Model Averaging),发展了一个NINO3.4指数的多模式客观权重集合预报方法(简称OBJ)。该方法基于训练期内单个模式的预报结果,用线性回归订正单个预报的偏差,依据模式的预报效果估计单个模式的权重。利用2002年2月—2015年10月美国哥伦比亚大学国际气候与社会研究所(IRI)提供的7个单一模式对NINO3.4指数的预报结果进行OBJ试验,并采用均方根误差对多模式集合平均预报(简称ENS)和OBJ的预报结果进行检验和评估。结果表明,ENS的预报效果优于7个单一模式的预报效果,而OBJ预报效果优于ENS预报效果,其NINO3.4指数的均方根误差比ENS方法降低了4%。将单一模式预报结果按时间划分为训练期和预报期,利用独立样本估计OBJ的参数并进行预报试验,这些试验也表明,OBJ能进一步提高预报精度。
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National Natural Science Foundation of China(41605043)National Key R&D Program of China(2016YFA0601504)Fundamental Research Funds for the Central Universities(2017B00114)。
文摘The Walker circulation(WC)has always been an important issue in atmospheric science research due to the association between the WC and tropical Pacific sea surface temperature(SST),and between the WC and ENSO events.In this paper,a new index-Omega index(OMGI)-is constructed for WC characterization based on the NCEP/NCAR reanalysis data of monthly mean vertical velocity in recent 70 years(1948-2017).Results show that the OMGI can accurately depict the variation characteristics of WC on seasonal,annual and decadal time-scales.There is a significant inverse correlation between the OMGI and equatorial eastern and central Pacific SST.Meanwhile,the peak of the OMGI appears ahead of the ENSO peak,and therefore is able to reflect the SST in the equatorial Pacific.Especially,in 35 ENSO events,the peak of the OMGI appears earlier than Ni?o 3.4 index for 19 times with 2.6 months ahead on average.In 16 El Ni?o events,the peak of the OMGI occurs ahead of the El Ni?o for 9 times with 4 months ahead on average.In19 La Ni?a events,the OMGI peak arises 10 times earlier than the La Ni?a peak,with an average of 1.4 months ahead.OMGI shows obvious leading effect and stability over ENSO events with different strengths and types of single peak and multi peaks:the peak of the OMGI keeps about 2-3 months ahead of the ENSO.Compared with other WC indexes such as UWI and SPLI,OMGI has some advantages in the ability to describe WC changes and present the probability and the time of prediction of ENSO event peaks.
文摘Abnormal weather conditions and extreme weather existed over the Kingdom Saudi Arabia (KSA) through the last decades. The present paper investigates the relationship between the Oceanic Nino Index (ONI) and variability of surface air temperature and precipitation rate over KSA through the period from 1950 to 2015 year. The NCEP/NCAR Reanalysis of monthly data sets of the mean surface air temperature and precipitation rate for the domain of the KSA is used. In addition, El Nino3.4 monthly data through the period (1950-2015) are used. For that period, the data set of the three months moving average of Nino3.4 anomaly, Oceanic Nino index (ONI), is used and analyzed. The time series, anomaly and correlation coefficient techniques are used to analyze the data sets through the present study. The results revealed that the KSA climate parameters, temperature and precipitation rates are controlled by ONI mainly in the autumn and winter seasons.
基金Supported by the National Basic Research Program of China(973 Program)(Nos.2012CB957704,2009CB723903)the National Natural Science Foundation of China(Nos.40506035,40876005)
文摘By analyzing the variability of global SST(sea surface temperature) anomalies,we propose a unified Ni o index using the surface thermal centroid anomaly of the region along the Pacific equator embraced by the 0.7°C contour line of the standard deviation of the SST anomalies and try to unify the traditional Ni o regions into a single entity.The unified Ni o region covers almost all of the traditional Ni o regions.The anomaly time series of the averaged SST over this region are closely correlated to historical Ni o indices.The anomaly time series of the zonal and meridional thermal centroid have close correlation with historical TNI(Trans-Ni o index) indices,showing differences among El Ni o(La Ni a) events.The meridional centroid anomaly suggests that areas of maximum temperature anomaly are moving meridionally(although slightly) with synchronous zonal movement.The zonal centroid anomalies of the unified Ni o region are found helpful in the classification of the Eastern Pacific(EP)/Central Pacific(CP) types of El Ni o events.More importantly,the zonal centroid anomaly shows that warm areas might move during a single warming/cooling phase.All the current Ni o indices can be well represented by a simple linear combination of unified Ni o indices,which suggests that the thermal anomaly(SSTA) and thermal centroid location anomaly of the unified Ni o region would yield a more complete image of each El Ni o/ La Ni a event.
