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961.
XU Huiand DUAN Wansuo State Laboratory of Numerical Modeling for Atmospheric Sciences Geophysical Fluid Dynamics 《大气科学进展》2008,(4)
With the Zebiak-Cane(ZC)model,the initial error that has the largest effect on ENSO prediction is explored by conditional nonlinear optimal perturbation(CNOP).The results demonstrate that CNOP-type errors cause the largest prediction error of ENSO in the ZC model.By analyzing the behavior of CNOP- type errors,we find that for the normal states and the relatively weak El Nino events in the ZC model,the predictions tend to yield false alarms due to the uncertainties caused by CNOP.For the relatively strong El Nino events,the ZC model largely underestimates their intensities.Also,our results suggest that the error growth of El Nino in the ZC model depends on the phases of both the annual cycle and ENSO.The condition during northern spring and summer is most favorable for the error growth.The ENSO prediction bestriding these two seasons may be the most diffcult.A linear singular vector(LSV)approach is also used to estimate the error growth of ENSO,but it underestimates the prediction uncertainties of ENSO in the ZC model.This result indicates that the different initial errors cause different amplitudes of prediction errors though they have same magnitudes.CNOP yields the severest prediction uncertainty.That is to say,the prediction skill of ENSO is closely related to the types of initial error.This finding illustrates a theoretical basis of data assimilation.It is expected that a data assimilation method can filter the initial errors related to CNOP and improve the ENSO forecast skill. 相似文献
962.
Emilia K. Jin James L. Kinter III B. Wang C.-K. Park I.-S. Kang B. P. Kirtman J.-S. Kug A. Kumar J.-J. Luo J. Schemm J. Shukla T. Yamagata 《Climate Dynamics》2008,31(6):647-664
The overall skill of ENSO prediction in retrospective forecasts made with ten different coupled GCMs is investigated. The coupled GCM datasets of the APCC/CliPAS and DEMETER projects are used for four seasons in the common 22 years from 1980 to 2001. As a baseline, a dynamic-statistical SST forecast and persistence are compared. Our study focuses on the tropical Pacific SST, especially by analyzing the NINO34 index. In coupled models, the accuracy of the simulated variability is related to the accuracy of the simulated mean state. Almost all models have problems in simulating the mean and mean annual cycle of SST, in spite of the positive influence of realistic initial conditions. As a result, the simulation of the interannual SST variability is also far from perfect in most coupled models. With increasing lead time, this discrepancy gets worse. As one measure of forecast skill, the tier-1 multi-model ensemble (MME) forecasts of NINO3.4 SST have an anomaly correlation coefficient of 0.86 at the month 6. This is higher than that of any individual model as well as both forecasts based on persistence and those made with the dynamic-statistical model. The forecast skill of individual models and the MME depends strongly on season, ENSO phase, and ENSO intensity. A stronger El Niño is better predicted. The growth phases of both the warm and cold events are better predicted than the corresponding decaying phases. ENSO-neutral periods are far worse predicted than warm or cold events. The skill of forecasts that start in February or May drops faster than that of forecasts that start in August or November. This behavior, often termed the spring predictability barrier, is in part because predictions starting from February or May contain more events in the decaying phase of ENSO. 相似文献
963.
基于SVD和修正Z指数的汛期旱涝预测及其应用 总被引:2,自引:0,他引:2
利用奇异值分解(SVD)方法、500hPa高度场、太平洋海温场和降水资料,建立起汛期降水的预测方程;经过适应本地化的Z指数修正,将预测结果转化为旱涝等级;将SVD技术与修正的Z指数结合起来,实现旱涝的气候预测;将研究成果推广应用到气象、防汛抗旱部门。结果表明:1)影响江淮分水岭地区汛期降水的因子有5个,分别是太平洋地区2个,印度半岛附近2个,欧洲地区1个;2)理论上的Z指数等级不符合江淮分水岭地区的实际状况,因而必须对Z指数进行修正。经过修正后的各个旱涝等级的划分概率较为合理,说明Z指数的5级指标是可靠的;3)利用5个影响因子可以建立汛期降水量与影响因子之间的预报方程,在共计8年的旱涝滚动预测和实况检验中,等级相符的有7年,只有2003年的预测试验相差一个等级,5级的预测准确率达到87.5%;4)经过气象、防汛抗旱部门2008年的应用,旱涝等级的预测意见和实际基本吻合,说明预测技术的应用情况良好。 相似文献
964.
SUN Jian-Qi 《大气和海洋科学快报》2010,3(4):232-236
This study examined the relationship between the boreal spring(April?May) Antarctic Oscillation(AAO) and the North American summer monsoon(NASM)(July?September) for the period of 1979?2008.The results show that these two systems are closely related.When the spring AAO was stronger than normal,the NASM tended to be weaker,and there was less rainfall over the monsoon region.The opposite NASM situation corresponded to a weaker spring AAO.Further analysis explored the possible mechanism for the delayed impact of the boreal spring AAO on the NASM.It was found that the tropical Atlantic sea surface temperature(SST) plays an important role in the connection between the two phenomena.The variability of the boreal spring AAO can produce anomalous SSTs over the tropical Atlantic.These SST anomalies can persist from spring to summer and can influence the Bermuda High,affecting water vapor transportation to the monsoon region.Through these processes,the boreal spring AAO exerts a significantly delayed impact on the amount of NASM precipitation.Thus,information about the boreal spring AAO is valuable for the prediction of the NASM. 相似文献
965.
2007年夏季降水异常的成因及预测 总被引:2,自引:0,他引:2
采用NCEP/NCAR再分析资料、NOAA再分析全球海温和中国国家气候中心整理的160站降水量资料,在回顾2007年夏季中国降水分布及其趋势预测的基础上,探讨了2007年夏季降水异常的可能原因。2007年前期对热带太平洋海温、东亚季风、西太平洋副热带高压等主要物理因子冬夏演变的分析接近实况,但主要多雨带位置仍比预测的偏南。夏季亚洲中纬度大陆高压异常维持可能是造成2007年夏季主要多雨带比预期偏南的主要原因。 相似文献
966.
A Bayesian probabilistic prediction scheme of the Yangtze River Valley (YRV) summer rainfall is proposed to combine forecast information from multi-model ensemble dataset provided by ENSEMBLES project.Due to the low forecast skill of rainfall in dynamic models,the time series of regressed YRV summer rainfall are selected as ensemble members in the new scheme,instead of commonly-used YRV summer rainfall simulated by models.Each time series of regressed YRV summer rainfall is derived from a simple linear regression.The predictor in each simple linear regression is the skillfully simulated circulation or surface temperature factor which is highly linear with the observed YRV summer rainfall in the training set.The high correlation between the ensemble mean of these regressed YRV summer rainfall and observation benefit extracting more sample information from the ensemble system.The results show that the cross-validated skill of the new scheme over the period of 1960 to 2002 is much higher than equally-weighted ensemble,multiple linear regression,and Bayesian ensemble with simulated YRV summer rainfall as ensemble members.In addition,the new scheme is also more skillful than reference forecasts (random forecast at a 0.01 significance level for ensemble mean and climatology forecast for probability density function). 相似文献
967.
以中国夏季气温为预测对象,选取东亚地区冬季500 h Pa高度场、海平面气压场、地表温度场和850 h Pa温度场为预测因子,采用1951~2009年去趋势处理后的资料,通过变形的典型相关分析(Barnett-Preisendorfer Canonical Correlation Analysis,BP-CCA)方法分别建立单因子预测模型,再利用集合典型相关分析(Ensemble Canonical Correlation,ECC)方法建立集合预测模型,对中国夏季气温进行基于交叉检验方法的预测试验,然后利用2010~2014年的资料对中国夏季气温进行独立样本检验。通过分析BP-CCA模态可知,一对BP-CCA模态的空间型在一定程度上可以反映预报因子场和对象场的遥相关特征。通过基于交叉检验方法的预测试验表明环流场和热力场均能为气温提供预测信息。ECC预测模型综合了各个预报因子的在不同地区的预报技巧,比单因子BP-CCA预测模型有更高、更稳定的预报技巧。独立样本检验表明ECC模型与单因子BP-CCA预测模型相比,对中国夏季气温有更高、更稳定的实际预测能力,对气温季节预测具有参考价值。 相似文献
968.
969.
970.
风能预报方法研究进展 总被引:8,自引:1,他引:7
中国蕴含着丰富的风能资源,但目前我国在风能预报方面的研究还很薄弱,几乎没有可用于风电场风能的客观、定量化的预报方法。风能预报,实际上最重要的是对风场的合理准确预报,进而得到风电量预报。通过简要介绍国际上风能预报的一些方法,如统计预报、动力预报(包括降尺度预报和集成预报)以及风电量预报,同时介绍对预报的检验和面向最终用户的预报平台的建设,希望能对我国风能预报行业的发展起到一定的借鉴和促进作用。 相似文献