共查询到18条相似文献，搜索用时 171 毫秒
1.
Recent advances in the study of nonlinear atmospheric and climate dynamics in China （2003 2006） are briefly reviewed. Major achievements in the following eight areas are covered： nonlinear error dynamics and predictability; nonlinear analysis of observational data; eddy-forced envelope Rossby soliton theory; sensitivity and stability of the ocean＇s thermohaline circulation; nonlinear wave dynamics; nonlinear analysis on fluctuations in the atmospheric boundary layer; the basic structures of atmospheric motions; some applications of variational methods. 相似文献
2.
Recent progress in the study of nonlinear atmospheric dynamics and related predictability of weather and climate in China (2007-2011) are briefly introduced in this article. Major achievements in the study of nonlinear atmospheric dynamics have been classified into two types:(1) progress based on the analysis of solutions of simplified control equations, such as the dynamics of NAO, the optimal precursors for blocking onset, and the behavior of nonlinear waves, and (2) progress based on data analyses, such as the nonlinear analyses of fluctuations and recording-breaking temperature events, the long-range correlation of extreme events, and new methods of detecting abrupt dynamical change. Major achievements in the study of predictability include the following:(1) the application of nonlinear local Lyapunov exponents (NLLE) to weather and climate predictability; (2) the application of condition nonlinear optimal perturbation (CNOP) to the studies of El Nin o-Southern Oscillation (ENSO) predictions, ensemble forecasting, targeted observation, and sensitivity analysis of the ecosystem; and (3) new strategies proposed for predictability studies. The results of these studies have provided greater understanding of the dynamics and nonlinear mechanisms of atmospheric motion, and they represent new ideas for developing numerical models and improving the forecast skill of weather and climate events. 相似文献
3.
Wansuo DUAN Lichao YANG Mu MU Bin WANG Xueshun SHEN Zhiyong MENG Ruiqiang DING 《大气科学进展》2023,(8):1521-1547
This article summarizes the progress made in predictability studies of weather and climate in recent years in China, with a main focus on advances in methods to study error growth dynamics and reduce uncertainties in the forecasting of weather and climate. Specifically, it covers(a) advances in methods to study weather and climate predictability dynamics, especially those in nonlinear optimal perturbation methods associated with initial errors and model errors and their applications to ensemble ... 相似文献
4.
This paper reviews the main theoretical progress of mesoscale weather dynamics since 2003, including： （1） The dynamic mechanisms of balanced and unbalanced flow are applied to study the genesis and development problems of mesoscale circulation. The symmetric instability and transverse-wave instability are analyzed in line and vortex atmosphere convection, and further research has been done on nonlinear convective symmetric instability. The interaction between forced convection and unstable convection and the wave characteristics of mesoscale motion are also discussed. （2） Intermediate atmosphere dynamic boundary layer models are developed. The complicated nonlinear interaction is analyzed theoretically between the atmospheric boundary layer and the free atmosphere. The structure of the topography boundary layer, atmospheric frontogenesis, the structure and circulation of the low-level front and other boundary layer dynamic problems are discussed. （3） The formation and development of meso-β-scale rainstorms under the background of the East-Asia atmosphere circulation are diagnosed with the variation of MPV （moist potential vorticity） anomalies. And some physical vectors are modified and applied in the moist atmosphere. 相似文献
5.
6.
EVOLUTION OF LARGE SCALE DISTURBANCES AND THEIR INTERACTION WITH MEAN FLOW IN A ROTATING BAROTROPIC ATMOSPHERE——PART Ⅰ 总被引：1，自引：0，他引：1
《大气科学进展》1986,(1)
The problems on evolution of large-scale disturbances and their interaction with mean flow recently attract much effort of meteorologists due to their practical importance in weather and climate predictions. In this paper, some theoretical results obtained in current investigations of these problems will be reviewed. A barotropic atmosphere is taken in this paper, and the baroclinic atmosphere is left in our second paper.The following aspects are reviewed: First, the general properties of two-dimensional barotropic motion both in the nonlinear and linearized equations and both in the quasi-geostrophic and non-geostrophic models. Second, the evolution and the structure of Rossby wave packet superimposed on a zonal or non-zonal basic flow.In this part, only the above two problems are reviewed. The remanent problems, i.e., the normal modes and continuous spectra of both quasi-geostrophic and non-geostrophic models, weakly nonlinear theory and the fully nonlinear theory will be discussed in part Ⅱ (another 相似文献
7.
With the high-speed development of numerical weather prediction, since the later 1980’s, the prediction of short-range climate anomalies has attracted worldwide meteorologists’ attention. What the so called short-range re-fers to the time scale from one month to one season or more. In dealing with the problem of short-range climate pre-diction, two points are needed noticing: one is the basic research to explore or investigate the mechanism of variability of the slow varying components which mainly include internal dynamics of extratropics, external forcings and tropical dynamics, and the other is the modeling efforts to simulate the process of the long-term evolution of the signal which include the improvement of model quality, stochastic prediction and the air-sea-coupled model (Miyakoda et al.,1986). Previous researches on the numerical prediction of short-term climate anomalies are mostly concentrated in the analysis of variables with global spatial scale, especially the global general atmospheric circulation analysis.As to the simulation or prediction of regional short-term climate anomalies, there exist many difficulties and problems. Though some meteorologists are devoting themself to this field, up to now, they have not reached satisfac-tory results. As a primary effort, by using the 2-level general atmospheric circulation model developed in the Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP-AGCM) (Zeng et al., 1989), and taking the year of 1985 as a case, a numerical simulation of regional short-term climate change is completed. We pay high attention to the predictand of anomalous summer rainfall in the Yangtze River and Yellow River valleys, especially its month-to-month variation. 相似文献
8.
The response of a grassland ecosystem to climate change is discussed within the context of a theoretical model.An optimization approach,a conditional nonlinear optimal perturbation related to parameter(CNOP-P) approach,was employed in this study.The CNOP-P,a perturbation of moisture index in the theoretical model,represents a nonlinear climate perturbation.Two kinds of linear climate perturbations were also used to study the response of the grassland ecosystem to different types of climate changes.The results show that the extent of grassland ecosystem variation caused by the CNOP-P-type climate change is greater than that caused by the two linear types of climate change.In addition,the grassland ecosystem affected by the CNOP-P-type climate change evolved into a desert ecosystem,and the two linear types of climate changes failed within a specific amplitude range when the moisture index recovered to its reference state.Therefore,the grassland ecosystem response to climate change was nonlinear.This study yielded similar results for a desert ecosystem seeded with both living and wilted biomass litter.The quantitative analysis performed in this study also accounted for the role of soil moisture in the root zone and the shading effect of wilted biomass on the grassland ecosystem through nonlinear interactions between soil and vegetation.The results of this study imply that the CNOP-P approach is a potentially effective tool for assessing the impact of nonlinear climate change on grassland ecosystems. 相似文献
9.
Recent Advances in Predictability Studies in China （1999-2002） 总被引：10，自引：2，他引：8
Since the last International Union of Geodesy and Geophysics (IUGG) General Assembly (1999), the predictability studies in China have made further progress during the period of 1999-2002. Firstly, three predictability sub-problems in numerical weather and climate prediction are classified, which are concerned with the maximum predictability time, the maximum prediction error, and the maximum allowable initial error, and then they are reduced into three nonlinear optimization problems. Secondly, the concepts of the nonlinear singular vector (NSV) and conditional nonlinear optimal perturbation (CNOP) are proposed,which have been utilized to study the predictability of numerical weather and climate prediction. The results suggest that the nonlinear characteristics of the motions of atmosphere and oceans can be revealedby NSV and CNOP. Thirdly, attention has also been paid to the relations between the predictability and spatial-temporal scale, and between the model predictability and the machine precision, of which the investigations disclose the importance of the spatial-temporal scale and machine precision in the study of predictability. Also the cell-to-cell mapping is adopted to analyze globally the predictability of climate,which could provide a new subject to the research workers. Furthermore, the predictability of the summer rainfall in China is investigated by using the method of correlation coefficients. The results demonstrate that the predictability of summer rainfall is different in different areas of China. Analysis of variance, which is one of the statistical methods applicable to the study of predictability, is also used to study the potential predictability of monthly mean temperature in China, of which the conclusion is that the monthly mean temperature over China is potentially predictable at a statistical significance level of 0.10. In addition,in the analysis of the predictability of the T106 objective analysis/forecasting field, the variance and the correlation coefficient are calculated to explore the distribution characteristics of the mean-square errors.Finally, the predictability of short-term climate prediction is investigated by using statistical methods or numerical simulation methods. It is demonstrated that the predictability of short-term climate in China depends not only on the region of China being investigated, but also on the time scale and the atmospheric internal dynamical process. 相似文献
10.
Weak ENSO Asymmetry Due to Weak Nonlinear Air–Sea Interaction in CMIP5 Climate Models 总被引：1，自引：0，他引：1
State-of-the-art climate models have long-standing intrinsic biases that limit their simulation and projection capabilities.Significantly weak ENSO asymmetry and weakly nonlinear air–sea interaction over the tropical Pacific was found in CMIP5(Coupled Model Intercomparison Project, Phase 5) climate models compared with observation. The results suggest that a weak nonlinear air–sea interaction may play a role in the weak ENSO asymmetry. Moreover, a weak nonlinearity in air–sea interaction in the models may be associated with the biases in the mean climate—the cold biases in the equatorial central Pacific. The excessive cold tongue bias pushes the deep convection far west to the western Pacific warm pool region and suppresses its development in the central equatorial Pacific. The deep convection has difficulties in further moving to the eastern equatorial Pacific, especially during extreme El Ni o events, which confines the westerly wind anomaly to the western Pacific. This weakens the eastern Pacific El Ni o events, especially the extreme El Ni o events, and thus leads to the weakened ENSO asymmetry in climate models. An accurate mean state structure(especially a realistic cold tongue and deep convection) is critical to reproducing ENSO events in climate models. Our evaluation also revealed that ENSO statistics in CMIP5 climate models are slightly improved compared with those of CMIP3. The weak ENSO asymmetry in CMIP5 is closer to the observation. It is more evident in CMIP5 that strong ENSO activities are usually accompanied by strong ENSO asymmetry, and the diversity of ENSO amplitude is reduced. 相似文献
11.
气候系统的非线性特征及其预测理论 总被引：1，自引：0，他引：1
本文针对气候问题的特殊性,对气候的定义、气候系统的非线性特征、演变机制、可预报性问题以及气候状态的预报方法等做了较全面的研究,这些内容初步形成了气候系统的准动力—准随机理论,是气候动力学的新发展。 相似文献
12.
与北极涛动或北半球环状模相关的纬向对称的正规模态 总被引：6，自引：3，他引：3
作为一个全球气候变率的重要模态,北极涛动或北半球环状模态(AO/NAM)一般由北半球海平面气压变率的EOF1来表示。但是通常认为EOF1仅有统计学意义而并不能够表明它是否是一种实际的物理模态。另一方面,现有的波-流相互作用理论也仅能给出纬向风的纬向平均状况,而不能够保证沿着某一纬圈的变化,所以它并不意味着一个具有半球尺度的纬向对称的相干结构能够组织起来。因此AO/NAM的形成机制仍然是一个具有争议的问题。文章提出纬向对称的或环状的正规模态与基本气候态附近的线性(进而非线性)动力学之间有着最直接的联系,因而可能在AO/NAM动力学的理解中扮演重要角色。为了深入探讨AO/NAM的动力学本质,使用p-坐标球面原始方程计算了冬季北半球及全球气候基本态附近的线性动力系统纬向对称的正规模态,发现在半球尺度上的纬向对称正规模态具有AO/NAM的经向偶极子及垂直方向近似正压的空间结构特征。而这些纬向对称正规模的时间变化尺度取决于与其他非纬向对称正规模间的相互作用。从而说明了AO/NAM可能是半球尺度上纬向对称正规模态的动力学行为的反映。 相似文献
13.
14.
15.
Summary An atmosphere-land coupled simple climate model is constructed and its climatic properties are analyzed by introducing a global analysis method, cell mapping. The simple model is a nonlinear six order simplified climate model featured with chaotic dynamics, dissipation, and forcing source, which are the main features of the real climate system. The cell mapping method is applied with this coupled system. Numerical experiments are carried out for investigating the interactions between the fast-changing atmospheric variables and slow-changing underlying surface variables. The predictability of the system is also investigated via the global analysis, with which the evolution of the system is translated to the evolution of probability transition on a Markov Chain. An effective scheme is proposed for computing the probability transition matrix for the coupled system. Predictions can be made based on the combination of dynamics and statistics. The importance of constructing the coupled model is shown by globally analyzing the predictability of the coupled system. The coupling mechanism prolongs the memorization of initial information, and then the predictability as well. 相似文献
16.
Summary Previous studies have highlighted the crucial role of sea surface temperature (SST) anomalies in the tropical Atlantic region
in forcing the summer monsoon rainfall over subsaharan West Africa. Understanding the physical processes, relating SST variations
to changes in the amount and distribution of African rainfall, is a key factor in improving weather and climate forecasts
in this highly vulnerable region.
Here, we present sensitivity experiments from a regional climate model with prescribed warmer tropical SSTs, according to
enhanced greenhouse conditions at the end of the 21st century. This dynamical downscaling approach provides information about
the nonlinear response of the atmosphere to oceanic heating. It has been suggested that the response is at least partly accounted
for by the linear theory of tropical dynamics, involving a Kelvin and Rossby wave response to a tropical heat source. We compute
the major modes of the linear Matsuno-Gill model for geopotential height and horizontal wind components and project the simulated
response patterns onto these linear modes, in order to evaluate to which extent the simple linear theory may explain the SST-induced
climate anomalies over Africa. A multivariate Hotelling T2 test is used to evaluate whether these anomalies are statistically significant.
Forcing the regional climate model by warmer SSTs leads to substantial climate anomalies over tropical Africa: Rainfall is
increases over the Guinea Coast region (GCR) and tropical East Africa, but decreases over the Congo Basin and the Sahel Zone
(SHZ). At the 850 hPa level, a trough develops over southern West Africa and the Gulf of Guinea, and is associated with stronger
surface wind convergence over the GCR. These changes in the atmospheric dynamics strongly project onto the leading modes of
the linear Matsuno-Gill model at various zonal wave numbers. The corresponding atmospheric heating pattern is highly reminiscent
of the simulated nonlinear model reponse. The T2 test statistics reveal that the SST forcing induces a statistically significant climate anomaly over tropical Africa if the
climate state vector is reduced by projecting the simulated data onto the leading 10 linear modes. It is also shown that the
linear response prevails in a long-term simulation with more realistic lower and lateral boundary conditions. Thus, linear
tropical dynamics are assumed to be a major physical process on the ground of the prominent SST-African rainfall relationship. 相似文献
17.
气候系统的非平稳行为和预测理论 总被引：22，自引：5，他引：17
到目前为止,有关非平稳复杂系统及其在气候预测中的应用研究(它有着比混沌系统更为复杂的行为)是一个较少被人理解并有重大科学意义的前瞻性研究课题。在大气运动中,气候正是一个典型的非平稳系统,但是现有的气候预测理论,包括统计预测理论和非线性预测理论,几乎都无一例外地建立在平稳性假定的基础之上,这有悖于气候过程的基本性质,因此它有可能是导致气候预测水平低下的重要的理论原因。另外,近10年来,气候过程具有层次结构已经成为许多科学家的共识,但是如何发展和完善这一理论,使之成为一个完整的体系,人们似乎还没找到合适的途径。事实上,气候系统的多层次结构(它与通常的多尺度结构是两个完全不同的概念)正是产生非平稳行为的原因,而气候系统的非平稳特性正是层次结构的集中表现。在这样的思想指导下,文中系统地讨论了非平稳气候的一些基本问题和相应的预测理论,并为之搭起了一个初步的理论框架。 相似文献
18.
Summary ¶The climate system can be regarded as a dynamic nonlinear system. Thus, traditional linear statistical methods fail to model the nonlinearities of such a system. These nonlinearities render it necessary to find alternative statistical techniques. Since artificial neural network models (NNM) represent such a nonlinear statistical method their use in analyzing the climate system has been studied for a couple of years now. Most authors use the standard Backpropagation Network (BPN) for their investigations, although this specific model architecture carries a certain risk of over-/ underfitting. Here we use the so called Cauchy Machine (CM) with an implemented Fast Simulated Annealing schedule (FSA) (Szu, 1986) for the purpose of attributing and detecting anthropogenic climate change instead. Under certain conditions the CM-FSA guarantees to find the global minimum of a yet undefined cost function (Geman and Geman, 1986).In addition to potential anthropogenic influences on climate (greenhouse gases (GHG), sulphur dioxide (SO2)) natural influences on near surface air temperature (variations of solar activity, explosive volcanism and the El Niño/Southern Oscillation phenomenon) serve as model inputs. The simulations are carried out on different spatial scales: global and area weighted averages. In addition, a multiple linear regression analysis serves as a linear reference.It is shown that the adaptive nonlinear CM-FSA algorithm captures the dynamics of the climate system to a great extent. However, free parameters of this specific network architecture have to be optimized subjectively. The quality of the simulations obtained by the CM-FSA algorithm exceeds the results of a multiple linear regression model; the simulation quality on the global scale amounts up to 81% explained variance. Furthermore the combined anthropogenic effect corresponds to the observed increase in temperature Jones et al. (1994), updated by Jones (1999a), for the examined period 1856–1998 on all investigated scales. In accordance to recent findings of physical climate models, the CM-FSA succeeds with the detection of anthropogenic induced climate change on a high significance level. Thus, the CM-FSA algorithm can be regarded as a suitable nonlinear statistical tool for modeling and diagnosing the climate system. 相似文献