大洋间SST遥联与亚太夏季风异常的关系

用奇异值分解(Singular Value Decomposition,SVD)方法,给出了四季年代际和年际时间尺度上北大西洋和北太平洋海表温度(Sea Surface Temperature,SST)的显著遥相关.用SVD主模态时间系数构造了海温异常指数Ⅰ,分析了它们与同期亚太夏季风和我国东部夏季降水异常的关系.结果表明:两大洋间的SST遥联在年际、年代际时间尺度上都与亚太夏季风相关,其中,年际尺度的两大洋SST遥联与长江流域的降水存在显著相关.     

Length Scales of Scalar Diffusion in the Convective Boundary Layer: Laboratory Observations

A laboratory study of scalar diffusion in the convective boundary layer has found results that are consistent with a 1999 large-eddy simulation (LES) study by Jonker, Duynkerke and Cuijpers. For bottom-up and top-down scalars (introduced as ‘infinite’ area sources of passive tracer at the surface and inversion, respectively) the dominant length scale was found to be much larger than the length scale for density fluctuations, the latter being equal to the boundary-layer depth h. The variance of the normalized passive scalar grew continuously with time and its magnitude was about 3–5 times larger for the top-down case than for the bottom-up case. The vertical profiles of the normalized passive scalar variance were found to be approximately constant through the convective boundary layer (CBL) with a value of about 3–8c_*² for bottom-up and 10–50c_*² for top-down diffusion. Finally, there was some evidence of a minimum in the variance and dominant length scale for scalar flux ratios (top-down to bottom-up flux) close to −0.5. All these convection tank results confirm the LES results and support the hypothesis that there is a distinct difference in behaviour between the dynamic and passive variables in the CBL.     

The autoparametric 3:2 resonance in conservative systems

In the resonance model, high‐frequency quasi‐periodic oscillations (QPOs) are supposed to be a consequence of nonlinear resonance between modes of oscillations occurring within the innermost parts of an accretion disk. Several models with a prescribed mode–mode interaction were proposed in order to explain the characteristic properties of the resonance in QPO sources. In this paper, we examine nonlinear oscillations of a system having a quadratic nonlinearity and we show that this case is particularly relevant for QPOs. We present a very convenient way how to study autoparametric resonances of a fully general system using the method of multiple scales. We concentrate to conservative systems and discuss their behavior near the 3:2 parametric resonance. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The Gordian knot of mangrove conservation: Disentangling the role of scale,services and benefits

Mangrove forests are among the most threatened tropical ecosystems. Their role as providers of important ecosystem services such as coastal protection, carbon storage and nursery habitats for economically important species is increasingly acknowledged. But mangrove destruction continues, and we might have to face the prospect of a world deprived of the services offered by mangrove ecosystems. Mangrove transformation and destruction is often caused by mismatches in mangrove system management. These root in interests that focus on selected ecosystem services only, but also result from a problem of fit between the spatial scales at which ecosystem services are provided, and those at which their benefits are realized. We argue that a combination of the ecosystem services concept with a careful approach to the issue of scales will help to overcome these problems and improve the management of mangrove systems. Drawing on two case studies from Indonesia and Brazil, we illustrate the relevance of our findings for different ecosystem services.     

多时间尺度环流对热带气旋海棠(0505)路径的影响

利用滤波方法将NCEP/NCAR提供的FNL风场资料分离出天气尺度和低频环流场,研究不同时间尺度环流对台风海棠（0505）路径的影响。热带气旋海棠路径的特征可以分两个主要阶段,在第一阶段,海棠西侧的天气尺度反气旋和低频流场副高南侧气流共同引导海棠向西南运动;第二阶段初期,天气尺度环流抑制海棠向北转向,但海棠西侧的QBW气旋和MJO尺度的气流共同引导海棠向北运动。海棠运动后期,海棠与低频气旋的相互作用导致了天气尺度流场中波列的产生和发展,形成了热带气旋的传播分量,令海棠产生了向东北转向的趋势,但是由于MJO环流场中副高的北抬和QBW气旋的引导,最终导致海棠向西运动。     

Problems of Oxfordian and Kimmeridgian stratigraphy in northern Central Siberia (Nordvik Peninsula section)

The Oxfordian–Lower Hauterivian section of the Nordvik Peninsula (northern Central Siberia) is a reference for developing zonal scales for various fossil groups and improving the Boreal zonal standard. In the middle 1950s–late 1980s, it was studied extensively by geologists, stratigraphers, lithologists, and experts on various fossil groups. These studies yielded rich fossil and microfossil collections and a set of parallel zonal scales for various faunal groups. Recently, a new detailed ammonite zonation of the Oxfordian and Kimmeridgian units of this section has been proposed. These results contradict the previous biostratigraphic data on ammonites, foraminifers, and palynomorphs. In the present paper, all the biostratigraphic data on the Oxfordian and Kimmeridgian units of the Nordvik Peninsula (Cape Urdyuk-Khaya) and northern Central Siberia undergo a comprehensive analysis and comparison with those on the Boreal Realm. The ammonite-constrained stratigraphic position of the lower Upper Jurassic in the Cape Urdyuk-Khaya section is interpreted as Upper Oxfordian or Middle Oxfordian. In our view, this difference in the understanding is due to the misidentification of some Oxfordian ammonite forms. The zones based on other fossil groups (foraminifers, dinocysts) which were distinguished in the Upper Oxfordian and Kimmeridgian sections of the Nordvik Peninsula are well traceable circumarctically. Their stratigraphic position in various regions of the Northern Hemisphere is constrained by ammonites and bivalves. However, if we use the last alternative ammonite zonation of this section part, hardly explicable contradictions will appear in interregional foraminiferal and dinocyst correlations.     

东北夏季降水预测技巧偏低的原因探讨

1978～2018年全国夏季降水实时业务预测技巧显示东北地区明显偏低,尤其是近几年在对全国夏季旱涝的总体分布预测效果明显提高的情况下,对东北地区的预测却与实况相反,因此有必要分析该区域预测技巧偏低的原因。利用站点资料、再分析格点数据、实时预测历史数据及统计诊断等方法,探讨了动力气候模式预测能力以及东北夏季降水预测的认识缺陷。通过系统地回顾东北夏季旱涝的气候特征、影响因子及预测方法等方面的研究进展,以及东北夏季降水实时预测检验,得出预测技巧偏低的可能原因:（1）东北初夏降水主要受东北冷涡活动的影响,盛夏主要受西太平洋副热带高压、东北南风和中高纬环流型的共同作用,而业务常用的国内外主要动力气候模式无法准确反映与东北初夏和盛夏降水相联系的关键环流系统;（2）东北夏季降水与全球海温的关系较弱且不稳定,尤其是与ENSO的关系较为复杂,年际关系随年代际变化而波动,即ENSO不是预测东北夏季降水的强信号;（3）东北夏季降水具有明显的季节内、年际和年代际等多时间尺度变率,夏季降水受到多种时间尺度信息的叠加和调控,不同尺度变率的贡献相当,且影响系统不同,导致预测难度较大。最后,进一步探讨了东北夏季降水预测存在的科学问题及可能的解决途径,以期为夏季业务预测提供参考。     

Determination and integration of appropriate spatial scales for river basin modelling

Appropriate spatial scales of dominant variables are determined and integrated into an appropriate model scale. This is done in the context of the impact of climate change on flooding in the River Meuse in Western Europe. The objective is achieved by using observed elevation, soil type, land use type and daily precipitation data from several sources and employing different relationships between scales, variable statistics and outputs. The appropriate spatial scale of a key variable is assumed to be equal to a fraction of the spatial correlation length of that variable. This fraction was determined on the basis of relationships between statistics and scale and an accepted error in the estimation of the statistic of 10%. This procedure resulted in an appropriate spatial scale for precipitation of about 20 km in an earlier study. The application to river basin variables revealed appropriate spatial scales for elevation, soil and land use of respectively 0·1, 5·3 and 3·3 km. The appropriate model scale is determined by multiplying the appropriate variable scales with their associated weights. The weights are based on SCS curve number method relationships between the peak discharge and some specific parameters like slope and curve number. The values of these parameters are dependent on the scale of each key variable. The resulting appropriate model scale is about 10 km, implying 225–250 model cells in an appropriate model of the Meuse basin meant to assess the impact of climate change on river flooding. The usefulness of the appropriateness procedure is in its ability to assess the appropriate scales of the individual key variables before model construction and integrate them in a balanced way into an appropriate model scale. Another use of the procedure is that it provides a framework for decisions about the reduction or expansion of data networks and needs. Copyright © 2003 John Wiley & Sons, Ltd.     

小波变换在位场资料去噪和位场分离中的应用

根据小波变换的原理,研究了小波阙值去噪方法和位场分离方法在某实测布格重力异常的应用及效果。多矩形棱柱体模型试验表明:选取合适的小波基和小波参数,可以更好地提取出重力异常中的有用信息,为下一步在实测重力数据中的应用提供理论基础。实测布格重力资料处理结果表明:基于小波变换的去噪方法和位场分离方法,能够较好地去除随机噪声,更好地区别出局部异常和区域异常,提高数据处理与解释中有用信号识别的精度。     

全球大气季节内振荡对长江流域持续暴雨影响的研究进展

在引证论述大气季节内振荡(ISO)对暴雨(强降水)重要作用的基础上,概括性地回顾影响长江流域持续暴雨的大气ISO基本特征及其形成机制的主要成果。重点针对全球热带内外不同时间尺度的大气ISO的空间变化和年际变化与长江流域持续暴雨之间联系的研究工作进行总结评述,较为完整地总结长江流域夏季降水季节内变化的气候特征和全球不同空间和时间尺度的ISO对东亚副热带地区持续暴雨影响的已有认识,并结合2个半球的ISO与长江流域持续暴雨关系的研究现状,对未来暴雨(强降水)与不同时尺度ISO相互作用及其在10～30 d延伸期预报中的应用中有价值的科学问题和研究热点进行探讨,以期强调南半球ISO变化在全球和东亚副热带气候系统中的重要地位,提高夏季长江流域持续暴雨10～30 d延伸期预报和旱涝气候预测准确率。