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1.
将气候预测中常用的74项环流特征量进行归一化处理后,与郑州市冬季气温进行相关普查,利用SVM(Support Vector Machine)两类分类方法,同时考虑气温的年代际变化,建立郑州冬季温度距平趋势预测推理模型,并对因子个数多少和年代际变化对预测模型的影响进行了试验.试验结果表明用25个和15个因子分别建模时,产生最优模型时样本平均Ts评分均为56%,但后者预报准确率为75%,较前者提高了10%.用20世纪50年代和60年代做试验集,效果较好,产生最优模型时的样本Ts评分和预报准确率较高;用90年代做试验集,效果较差. 相似文献
2.
利用1951—2012年冬季全国160个站月平均气温以及NCEP/NACR再分析资料和海温、北极海冰等资料,分析了我国冬季气温及其关键影响因子的年代际变化特征,重点研究了关键影响因子对我国冬季气温影响关系的年代际变化。研究表明:我国冬季气温在1985年之前处于冷期,之后为暖期; 我国冬季气温异常与影响因子的关系发生了显著的年代际变化,而且影响因子之间的关系也发生了显著的年代际变化。针对这种年代际变化的基本事实,提出针对冷期和暖期中不同影响因子与冬季气温的关系分时段建立冬季气温的多因子回归预测模型,可以反映冬季气温及其影响因子关系的年代际变化特征。正确的预测策略是利用相同年代际背景下预测对象与预测因子的时间序列资料建立预测模型,以确保预测模型中反映的预测对象与预测因子关系的稳定性,进而保持较高的拟合及预测水平。 相似文献
3.
选取前期9、6和3个月欧亚大陆地表温度、东北半球500 h Pa高度场、热带印度洋海表面温度和西太平洋海表面温度作为预报因子,使用变形的典型相关分析(BP-CCA)方法,并选取各因子预报效果最好的时期作为关键时期,建立起各因子和青藏高原冬季气温之间的统计降尺度模型。之后用交叉验证和集合典型相关分析(ECC)方法评估模型实际预报能力。进一步用独立样本检验来评估模型更长时间尺度的年际变化预测效果。结果表明,BP-CCA方法能很好地识别出不同因子影响青藏高原的空间模态。其中,温度积雪反照率的正反馈机制体现了欧亚大陆地表温度的可预报性;东北半球500 h Pa高度场环流型不利于高纬的冷空气入侵高原地区;热带印度洋海表面温度反映出典型的印度洋偶极子对高原气温的调控作用;西太平洋海表面温度通过控制副热带高压的位置,从而影响高原冬季气温。各因子预报场和观测场的相关系数在交叉检验和独立样本检验中分别约为0.5和0.3,均有一定的预报技巧。而利用ECC方法能综合各因子所提供的预报信息,从而得出更为可信和稳定的预报。 相似文献
4.
5.
淮河流域大气环流型在冬季气温预测中的应用 总被引：1，自引：0，他引：1
应用Lamb-Jenkinson大气环流分型方法,根据由1970—2012年NCEP/NCAR逐日海平面气压场计算得到的环流指数,对淮河流域的环流进行分型。分析了冬季主要环流型和气温的分布特征及两者的联系,并以环流指数和主要环流型为预测因子,结合经验正交函数分解(EOF)方法和逐步回归方法,建立了淮河流域冬季气温距平的预测模型。结果表明,淮河流域冬季的主要环流型是东北风型、东风型、反气旋环流型以及东北风、东风配合下的反气旋性环流型,划分的环流型符合实际情况,这些环流型具有显著的年际和年代际变化特征。通过对预测模型进行后报试验和独立预报试验,表明该模型具有一定的预报技巧。 相似文献
6.
利用T639模式预报产品和黑龙江省83个国家气象站气温实况观测资料,采用最优预报因子方法选取预报因子,应用多元回归方法建立逐站日最高气温和日最低气温的MOS预报方程; 对MOS、中央气象台指导预报（SCMOC）和T639三种气温预报产品的日最高气温和日最低气温预报效果进行对比检验分析,并用EOF方法检验预报与实况的时空变化特征一致性。结果表明: 与实况的时空变化一致性方面,MOS和SCMOC较好,T639略差; 预报效果方面,MOS和SCMOC对日最高气温和日最低气温的2 ℃预报准确率普遍高于T639,MOS的预报准确率在日最高气温方面高于SCMOC,在日最低气温方面低于SCMOC; MOS对T639气温预报产品改善效果明显,尤其对冬季日最低气温的预报改善效果十分显著; MOS较T639气温预报改善效果与T639模式预报效果呈负相关关系,主要表现为,MOS预报改善效果在T639预报准确率低的山区明显优于平原,在春、夏季,预报准确率较低的日最高气温明显优于日最低气温,在冬季,预报准确率较低的日最低气温优于日最高气温; MOS气温预报方法的预报性能较理想,SCMOC对黑龙江省预报难度较大的日最低气温预报效果较好。 相似文献
7.
利用参加第六次国际耦合模式比较计划（CMIP6）年代际气候预测计划（DCPP）的加拿大CanESM5模式和日本MIROC6模式的结果,评估了模式对中国近地面气温的预测能力。在年代际尺度上,两个模式年代际试验对近地面气温的回报技巧均高于历史试验的模拟能力,采用海温初始化可以提高模式对中国近地面气温的年代际预报技巧。对年代际回报试验的进一步分析表明,两个模式均能较好地预测年平均气温的变化;对季节平均气温,模式在秋季的回报技巧最高,在冬季较低。就区域平均气温而言,两个模式对中国各个地区年平均和季节平均气温都有较高的回报技巧,其中我国南方和西部地区的气温回报技巧比北方高。年平均以及春季、冬季的气温年代际回报技巧总体随提前时间的增加而降低,夏季和秋季的气温回报技巧随提前时间的增加提高。各区域内年代际预测技巧随提前时间的变化特征与全国整体基本一致。 相似文献
8.
通过简要回顾中国学者有关东北三省冬季气温变化的研究成果,概括分析了近百年或近几十年时间尺度平均气温及最高、最低气温年际、年代际变化的基本特征,综述了与冬季气温年际、年代际变化相关的各类海-气环流因子。近百年来,东北冬季气温上升,1987年前后发生增暖突变;北极涛动、西伯利亚高压、东亚冬季风等是影响东北冬季气温年际变化的主要因子;北极涛动、东亚冬季风、东亚中高纬环流型等的持续性是冬季气温年代际变化的主要因子。对多种变化特征集中出现的20世纪70年代末的气候变化值得深入探讨,也有必要在整个东北三省的范围内,深入开展冬季气温预测方法的系统研究。另外,测站气温序列的非均一性问题也应引起足够重视。 相似文献
9.
通过统计铜川单站53a历史气候,用Spss11.5对铜川站历史各项气象要素与各月平均气温、降水量进行相关性分析,找出前期各气象要素与预报月的降水、气温相关性好的因子,用逐步回归方法进行模拟,得出铜川站的月平均降水、气温预报模型,用可视化语言Visual Basic 6.0程序设计中的Adodc数据库技术方法,分别建立了铜川站的月降水、平均气温预测因子数据库,63个相关性较好的因子进入模型,实现自动预测,并以Datagrib表格显示预测结果和预测因子组合。从近三年预测结果看,降水距平百分率在20%以内的准确率为30.6%;气温预报误差在1℃以内的准确率为50.0%。需要在实际业务中进一步检验,找出预报和实况的误差关系。 相似文献
10.
利用典型相关分析(CCA)方法建立统计气候预测模型，对我国冬季气温进行了预测试验，采用历史资料独立样本检验的方法，对预报技巧给出合理的评定。结果表明，使用CCA方法对我国冬季气温进行短期气候预测，有一定的预报技巧，对于特定地区和特定时期优选的因子场组合，可以取得较为满意的预报效果。大部分地区的季平均预报时效在2个季以内时，最佳预报相关系数在0.5以上。季平均的预报水平明显高于月平均的预报。海温场是所有因子场中最好的预报因子，不仅单独海温场的预报效果较好，而且与其他因子场组合后的预报水平还可以得到进一步提高。 相似文献
11.
年代际气候预测计划（DCPP）是第六次国际耦合模式比较计划（CMIP6）的子计划之一,其目标是利用多模式开展气候系统年代际预测、可预测性和变率机制研究。DCPP设计了3组试验,即年代际回报试验、预报试验以及理解年代际变率机制和可预测性的敏感性试验。目前有21个模式拟参与DCPP计划,其中包括5个来自中国的模式。DCPP将推动解决气候系统从年际到年代际尺度预测相关的多项科学问题,评估当前气候预测系统预报技巧,挖掘潜在可预报性,研究长时间尺度气候变率形成机制,提供对科学和社会有用的预测产品。 相似文献
12.
利用我国541个测站1960—2010年气温资料以及国家气候中心参加第5次耦合模式比较计划 (CMIP5) 的气候系统模式BCC_CSM1.1的历史试验和年代际试验结果,评估了该模式对我国近50年气温变化特征的模拟能力, 对模式的年代际试验结果进行了误差订正,并给出未来10~20年我国气温变化的预估。结果表明:历史试验和年代际试验均模拟出了与观测较为一致的增暖趋势,但均没有观测资料的增暖幅度大。其中,历史试验比年代际试验更接近于观测。年代际尺度上,模式对我国东部的模拟要好于西部;年际尺度上,模式的高预报技巧区在我国西北地区西南部和东部、西南地区北部。历史试验和年代际试验对我国气温空间场整体分布模拟较好,误差订正后的年代际试验结果对空间气温场的模拟有更好把握。相对于观测资料得到的1960—2010年0.27℃/10 a的增温速率,模式预估我国2011—2030年平均气温变化速率达到0.48℃/10 a, 上升趋势更加明显。 相似文献
13.
Three-Dimensional Structure of Optimal Nonlinear Excitation for Decadal Variability of the Thermohaline Circulation 
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下载免费PDF全文 The decadal variability of the North Atlantic thermohaline circulation（THC） is investigated within a three-dimensional ocean circulation model using the conditional nonlinear optimal perturbation method. The results show that the optimal initial perturbations of temperature and salinity exciting the strongest decadal THC variations have similar structures： the perturbations are mainly in the northwestern basin at a depth ranging from 1500 to 3000 m. These temperature and salinity perturbations act as the optimal precursors for future modifications of the THC, highlighting the importance of observations in the northwestern basin to monitor the variations of temperature and salinity at depth. The decadal THC variation in the nonlinear model initialized by the optimal salinity perturbations is much stronger than that caused by the optimal temperature perturbations, indicating that salinity variations might play a relatively important role in exciting the decadal THC variability. Moreover, the decadal THC variations in the tangent linear and nonlinear models show remarkably different characteristics, suggesting the importance of nonlinear processes in the decadal variability of the THC. 相似文献
14.
S. Kravtsov 《Climate Dynamics》2012,39(9-10):2377-2391
This paper assesses potential predictability of decadal variations in the El Ni?o/Southern Oscillation (ENSO) characteristics by constructing and performing simulations using an empirical nonlinear stochastic model of an ENSO index. The model employs decomposition of global sea-surface temperature (SST) anomalies into the modes that maximize the ratio of interdecadal-to-subdecadal SST variance to define low-frequency predictors called the canonical variates (CVs). When the whole available SST time series is so processed, the leading canonical variate (CV-1) is found to be well correlated with the area-averaged SST time series which exhibits a non-uniform warming trend, while the next two (CV-2 and CV-3) describe secular variability arguably associated with a combination of Atlantic Multidecadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO) signals. The corresponding ENSO model that uses either all three (CVs 1–3) or only AMO/PDO-related (CVs 2 and 3) predictors captures well the observed autocorrelation function, probability density function, seasonal dependence of ENSO, and, most importantly, the observed interdecadal modulation of ENSO variance. The latter modulation, and its dependence on CVs, is shown to be inconsistent with the null hypothesis of random decadal ENSO variations simulated by multivariate linear inverse models. Cross-validated hindcasts of ENSO variance suggest a potential useful skill at decadal lead times. These findings thus argue that decadal modulations of ENSO variability may be predictable subject to our ability to forecast AMO/PDO-type climate modes; the latter forecasts may need to be based on simulations of dynamical models, rather than on a purely statistical scheme as in the present paper. 相似文献
15.
Multi-year predictability in a coupled general circulation model 总被引：1，自引：0，他引：1
Multi-year to decadal variability in a 100-year integration of a BMRC coupled atmosphere-ocean general circulation model (CGCM)
is examined. The fractional contribution made by the decadal component generally increases with depth and latitude away from
surface waters in the equatorial Indo-Pacific Ocean. The relative importance of decadal variability is enhanced in off-equatorial
“wings” in the subtropical eastern Pacific. The model and observations exhibit “ENSO-like” decadal patterns. Analytic results are
derived, which show that the patterns can, in theory, occur in the absence of any predictability beyond ENSO time-scales.
In practice, however, modification to this stochastic view is needed to account for robust differences between ENSO-like decadal
patterns and their interannual counterparts. An analysis of variability in the CGCM, a wind-forced shallow water model, and
a simple mixed layer model together with existing and new theoretical results are used to improve upon this stochastic paradigm
and to provide a new theory for the origin of decadal ENSO-like patterns like the Interdecadal Pacific Oscillation and Pacific
Decadal Oscillation. In this theory, ENSO-driven wind-stress variability forces internal equatorially-trapped Kelvin waves
that propagate towards the eastern boundary. Kelvin waves can excite reflected internal westward propagating equatorially-trapped
Rossby waves (RWs) and coastally-trapped waves (CTWs). CTWs have no impact on the off-equatorial sub-surface ocean outside
the coastal wave guide, whereas the RWs do. If the frequency of the incident wave is too high, then only CTWs are excited.
At lower frequencies, both CTWs and RWs can be excited. The lower the frequency, the greater the fraction of energy transmitted
to RWs. This lowers the characteristic frequency (reddens the spectrum) of variability off the equator relative to its equatorial
counterpart. At low frequencies, dissipation acts as an additional low pass filter that becomes more effective, as latitude
increases. At the same time, ENSO-driven off-equatorial surface heating anomalies drive mixed layer temperature responses
in both hemispheres. Both the eastern boundary interactions and the accumulation of surface heat fluxes by the surface mixed
layer act to low pass filter the ENSO-forcing. The resulting off-equatorial variability is therefore more coherent with low
pass filtered (decadal) ENSO indices [e.g. NINO3 sea-surface temperature (SST)] than with unfiltered ENSO indices. Consequently
large correlations between variability and NINO3 extend further poleward on decadal time-scales than they do on interannual
time-scales. This explains why decadal ENSO-like patterns have a broader meridional structure than their interannual counterparts.
This difference in appearance can occur even if ENSO indices do not have any predictability beyond interannual time-scales.
The wings around 15–20°S, and sub-surface variability at many other locations are predictable on interannual and multi-year
time-scales. This includes westward propagating internal RWs within about 25° of the equator. The slowest of these take up
to 4 years to reach the western boundary. This sub-surface predictability has significant oceanographic interest. However,
it is linked to only low levels of SST variability. Consequently, extrapolation of delayed action oscillator theory to decadal
time-scales might not be justified. 相似文献
16.
在工业革命以来全球长期增暖趋势背景下,全球平均表面气温还同时表现出年代际变化特征,二者叠加在一起使得全球平均气温在某些年份增暖相对停滞(如1999～2008年)或者增暖相对较快(如1980～1998年).利用中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室(LASG)发展的耦合气候模式FGOALS-s2历史气候和典型路径浓度(RCPs)模拟试验结果研究了可能造成全球增暖的年代际停滞及加速现象的原因,特别是海洋环流对全球变暖趋势的调制作用.该模式模拟的全球平均气温与观测类似,即在长期增暖趋势之上,还叠加了显著的年代际变化.对全球平均能量收支分析表明,模拟的气温年代际变化与大气顶净辐射通量无关,意味着年代际表面气温变化可能与能量在气候系统内部的重新分配有关.通过对全球增暖加速和停滞时期大气和海洋环流变化的合成分析及回归分析,发现全球表面气温与大部分海区海表温度(SST)均表现出几乎一致的变化特征.在增暖停滞时期,SST降低,更多热量进入海洋次表层和深层,使其温度增加;而在增暖加速时期,更多热量停留在表层,使得大部分海区SST显著增加,次表层海水和深海相对冷却.进一步分析表明,热带太平洋表层和次表层海温年代际变化主要是由于副热带—热带经圈环流(STC)的年代际变化所致,然后热带太平洋海温异常可以通过风应力和热通量强迫作用引起印度洋、大西洋海温的年代际变化.在此过程中,海洋环流变化起到了重要作用,例如印度尼西亚贯穿流(ITF)年代际异常对南印度洋次表层海温变化起到关键作用,而大西洋经圈翻转环流(AMOC)则能直接影响到北大西洋深层海温变化. 相似文献
17.
That a model has sensitivity responses to parameter uncertainties is a key concept in implementing model parameter estimation using filtering theory and methodology.Depending on the nature of associated physics and characteristic variability of the fluid in a coupled system,the response time scales of a model to parameters can be different,from hourly to decadal.Unlike state estimation,where the update frequency is usually linked with observational frequency,the update frequency for parameter estimation must be associated with the time scale of the model sensitivity response to the parameter being estimated.Here,with a simple coupled model,the impact of model sensitivity response time scales on coupled model parameter estimation is studied.The model includes characteristic synoptic to decadal scales by coupling a long-term varying deep ocean with a slow-varying upper ocean forced by a chaotic atmosphere.Results show that,using the update frequency determined by the model sensitivity response time scale,both the reliability and quality of parameter estimation can be improved significantly,and thus the estimated parameters make the model more consistent with the observation.These simple model results provide a guideline for when real observations are used to optimize the parameters in a coupled general circulation model for improving climate analysis and prediction initialization. 相似文献
18.
We analyze decadal climate variability in the Mediterranean region using observational datasets over the period 1850–2009 and a regional climate model simulation for the period 1960–2000, focusing in particular on the winter (DJF) and summer (JJA) seasons. Our results show that decadal variability associated with the winter and summer manifestations of the North Atlantic Oscillation (NAO and SNAO respectively) and the Atlantic Multidecadal Oscillation (AMO) significantly contribute to decadal climate anomalies over the Mediterranean region during these seasons. Over 30% of decadal variance in DJF and JJA precipitation in parts of the Mediterranean region can be explained by NAO and SNAO variability respectively. During JJA, the AMO explains over 30% of regional surface air temperature anomalies and Mediterranean Sea surface temperature anomalies, with significant influence also in the transition seasons. In DJF, only Mediterranean SST still significantly correlates with the AMO while regional surface air temperature does not. Also, there is no significant NAO influence on decadal Mediterranean surface air temperature anomalies during this season. A simulation with the PROTHEUS regional ocean–atmosphere coupled model is utilized to investigate processes determining regional decadal changes during the 1960–2000 period, specifically the wetter and cooler 1971–1985 conditions versus the drier and warmer 1986–2000 conditions. The simulation successfully captures the essence of observed decadal changes. Model set-up suggests that AMO variability is transmitted to the Mediterranean/European region and the Mediterranean Sea via atmospheric processes. Regional feedbacks involving cloud cover and soil moisture changes also appear to contribute to observed changes. If confirmed, the linkage between Mediterranean temperatures and the AMO may imply a certain degree of regional decadal climate predictability. The AMO and other decadal influences outlined here should be considered along with those from long-term increases in greenhouse gas forcings when making regional climate out-looks for the Mediterranean 10–20?years out. 相似文献
19.
太平洋年代际振荡（PDO）是北太平洋海表温度年代际变率的主模态。由于太平洋年代际振荡对区域乃至全球气候的显著影响,其合理的预测结果可以带来多方面收益。然而,针对太平洋年代际振荡及其有关的海表温度的年代际预测,目前气候模式的预测水平还十分有限,因此,提出了一个新的增量方法。一系列的验证结果表明,增量方法可以有效预测太平洋年代际振荡,其中包括成功预测出其振荡的年代际转折。增量方法的预测过程主要包括3个步骤:（1）采用5 a滑动平均得到太平洋年代际振荡的年代际变率;（2）利用3 a增量形式的预测因子构建预测模型,预测3 a增量的太平洋年代际振荡（DI_PDO）;（3）将预测得到的DI_PDO加上3 a前的观测PDO,得到最后预测的PDO。增量方法亦可以应用到气候系统年代际内部变率的其他模态（如:北大西洋年代际振荡）和其他气候变量的年代际预测（如:海表温度）。 相似文献
20.
The effect of vegetation feedback on decadal-scale Sahel rainfall variability is analyzed using an ensemble of climate model simulations in which the atmospheric general circulation model ICTPAGCM (“SPEEDY”) is coupled to the dynamic vegetation model VEGAS to represent feedbacks from surface albedo change and evapotranspiration, forced externally by observed sea surface temperature (SST) changes. In the control experiment, where the full vegetation feedback is included, the ensemble is consistent with the observed decadal rainfall variability, with a forced component 60 % of the observed variability. In a sensitivity experiment where climatological vegetation cover and albedo are prescribed from the control experiment, the ensemble of simulations is not consistent with the observations because of strongly reduced amplitude of decadal rainfall variability, and the forced component drops to 35 % of the observed variability. The decadal rainfall variability is driven by SST forcing, but significantly enhanced by land-surface feedbacks. Both, local evaporation and moisture flux convergence changes are important for the total rainfall response. Also the internal decadal variability across the ensemble members (not SST-forced) is much stronger in the control experiment compared with the one where vegetation cover and albedo are prescribed. It is further shown that this positive vegetation feedback is physically related to the albedo feedback, supporting the Charney hypothesis. 相似文献