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1.
Zhaoyang CHAI He ZHANG Mulan ZHANG Xiao TANG Weipeng ZHENG Jiang ZHU Guangqing ZHOU Junji CAO Qingcun ZENG 《大气科学进展》2021,38(10):1611-1620
This article introduces "EarthLab ", a major new Earth system numerical simulation facility developed in China.EarthLab is a numerical simulation system for a physical climate system, an environmental system, an ecological system, a solid earth system, and a space weather system as a whole with a high-performance scientific computing platform.EarthLab consists of five key elements—namely: a global earth numerical simulation system, a regional high-precision simulation system, a supercomputing support and management system, a database, data assimilation and visualization system, and a high-performance computing system for earth sciences. EarthLab helps to study the atmosphere, hydrosphere,cryosphere, lithosphere, and biosphere, as well as their interactions, to improve the accuracy of predictions by integrating simulations and observations, and to provide a scientific foundation for major issues such as national disaster prevention and mitigation. The construction and operation of EarthLab will involve close cooperation with joint contributions and shared benefits. 相似文献
2.
采用均一化订正的北京南郊地面日平均气温资料,分析了北京地区1951—2008年气温变化趋势。结果表明,年平均最高和最低气温的升高呈明显的不对称性,其中年平均最低气温升高较为明显,升温趋势为0.46℃/10a。根据1951—2008年日平均气温计算北京春、夏、秋、冬四季的季节长度和起始日期,发现北京地区冬季最长,秋季最短;夏季在逐渐延长,冬季在逐渐缩短,夏、冬两季长度变化的线性速率分别为4.4d/10a和-4.7d/10a。春、夏两季逐渐提前,趋势分别为3.0d/10a和2.5d/10a;而秋、冬两季在逐渐推迟,趋势分别为2.0d/10a和1.7d/10a。将季节起始日期与年平均气温进行相关性分析发现,春、夏两季的起始时间与年平均气温存在显著负相关,而秋、冬两季起始时间与年平均气温存在显著正相关。 相似文献
3.
The interplay between the North Atlantic Oscillation (NAO) and the large scale ocean circulation is inspected in a twentieth century simulation conducted with a state-of-the-art coupled general circulation model. Significant lead–lag covariance between oceanic and tropospheric variables suggests that the system supports a damped oscillatory mode involving an active ocean–atmosphere coupling, with a typical NAO-like space structure and a 5 years timescale, qualitatively consistent with a mid-latitude delayed oscillator paradigm. The two essential processes governing the oscillation are (1) a negative feedback between ocean gyre circulation and the high latitude SST meridional gradient and (2) a positive feedback between SST and the NAO. The atmospheric NAO pattern appears to have a weaker projection on the ocean meridional overturning, compared to the gyre circulation, which leads to a secondary role for the thermohaline circulation in driving the meridional heat transport, and thus the oscillatory mode. 相似文献
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The horizontal and vertical wind velocity fluctuations were measured using two sonic anemometers at a height of 135 cm above
a snow surface under a transverse snow wave-forming condition. A snow-wave was formed when the wind at a height of 1 m blew
at a speed of more than 7 m s−1 after an approximate accumulation of from 10 to 20 cm of new snow on a snowfield. For example, when a snow-wave had a wavelength
of 10 m and a wave height of 15 to 20 cm, the measured horizontal and vertical velocity components showed that they had a
frequency peak of 0.7 Hz in coherence and co-spectrum corresponding to this wavelength. The results suggest that wind turbulence
and snow-wave formation interact with each other. 相似文献
6.
The horizontal and vertical wind velocity fluctuations were measured using two sonic anemometers at a height of 135 cm above a snow surface under a transverse snow wave-forming condition. A snow-wave was formed when the wind at a height of 1 m blew at a speed of more than 7 m s–1 after an approximate accumulation of from 10 to 20 cm of new snow on a snowfield. For example, when a snow-wave had a wavelength of 10 m and a wave height of 15 to 20 cm, the measured horizontal and vertical velocity components showed that they had a frequency peak of 0.7 Hz in coherence and co-spectrum corresponding to this wavelength. The results suggest that wind turbulence and snow-wave formation interact with each other. 相似文献
7.
1951~2008年北京极端天气事件分析 总被引：3，自引：0，他引：3
应用1951~2008北京国家气候观象台的气温、降水、雷暴、雾、沙尘、大风、霜冻、相对湿度等逐日观测资料以及逐时降水资料, 分析了北京极端天气事件的变化趋势。结果表明：（1）年平均气温、极端最低气温分别以0.39 ℃·(10 a) -1、1.0 ℃·(10 a) -1的趋势升高;轻雾天气增加趋势比较明显[12.4 d·(10 a)-1];日最大降水量以-10.8 mm·(10 a)-1的速率呈渐弱趋势;降水日数、相对湿度、大风和雷暴天气均有不同程〖JP2〗度的减少,变化趋势分别为-1.90 d·(10 a)-1、-1.17% (10 a)-1、-2.64 d·(10 a)-1和-1.24 d·(10 a)-1;沙尘天气减少较明显[-9.39 d·(10 a)-1];极端最高气温、小时雨强最大值、暴雨天气日数、霜冻、大雾、高温天气日数波动幅度较大,总体变化趋势不明显。（2）暴雨、高温、极端最高温度和沙尘事件不存在明显的周期性变化;大风、大雾事件周期性特征在不同时段表现不同。雷暴、霜冻、极端最低温度、日最大降水量事件分别有6年、7年、16年、12年左右的周期性变化。轻雾除存在12年左右的主周期外,不同时段具有不同尺度次周期。（3）城市的扩展对记录到的变暖趋势有重要的贡献。各种极端天气事件与特定的天气系统相联系,受城市发展影响可能较小。 相似文献
8.
T. Vrhovec 《Meteorology and Atmospheric Physics》1991,46(1-2):91-99
Summary A formation of a cold air lake in a basin is studied with a mesometeorological model.A dynamic Boussinesq hydrostatic mesoscale numerical model is developed in a staggered orthogonal grid with a horizontal resolution of 1 km and with a varying vertical grid. The topography is presented in a block shape so that computation levels are horizontal.The mesometeorological model is tested in three idealized topography cases (a valley, a single mountain, a basin) and test results are discussed.In an alpine basin surrounded by mountains and plateaus the air is supposed to be stagnant at the beginning of the night. Due to differences in radiation cooling an inversion layer is formed in the basin and local wind circulation is studied by model simulations.With 14 Figures 相似文献
9.
Knowledge on climate change impacts, adaptation, and vulnerability is fragmented, because it is found in disparate case studies which use inconsistent terminology and focus on distinct aspects relevant to adaptation. While large-scale syntheses such as the Assessment Reports of the Intergovernmental Panel on Climate Change provide a high level overview and are useful for international decision-making, there is a need for systematic and flexible access to this research-based knowledge in order to aid future adaptation research and decision-making. Against this background, we present a ‘conceptual’ meta-analysis, a novel approach to meta-analyse studies on climate change impacts, adaptation, and vulnerability in Europe. The meta-analysis results in a classification scheme for relating the diverse studies. This scheme consists of (i) a classification of studies according to the type of adaptation-relevant results they produce and (ii) a hierarchical classification of the regional and thematic context of studies. The implementation of this scheme, for example in the form of a database, overcomes some of the identified gaps of current adaptation knowledge representation. We furthermore present a quantitative analysis of the classified studies that exemplifies how the developed classification scheme can be applied to get a systematic and quantitative overview of the knowledge they contain. Thus, the conceptual meta-analysis and the classification scheme represent a first step towards a systematisation of knowledge on climate change impacts, adaptation, and vulnerability and may be seen as a useful complement to qualitative literature reviews. 相似文献
10.
基于分拆数的角色访问控制模型的原理与实现 总被引：2，自引：0，他引：2
介绍了基于分拆数的权限管理策略的原理及其在角色访问控制模型中的应用，实现了一个结构简单、伸缩性好、功能强大的权限管理系统。提出了自然数按集合分拆的新概念，同时给出了一个自然数按某个有限集狭义分拆唯一的充分条件。 相似文献
11.
建立清代1644—1911年广东的旱涝指数序列,采用滑动t检验、完备总体经验模态函数分析了清代广东旱涝的突变特征和多时间尺度周期性特征。结果表明,清代广东旱涝指数整体较平稳,呈现先明显增加后减少、后略微增加的趋势。旱涝指数序列具有多个跃变点,且有年际尺度4.2 a和7.8 a,年代际尺度11.6 a、15.2 a、36.5 a和70.1 a,世纪尺度130.3 a左右的周期。发现广东旱涝有多个周期与太阳黑子相对数序列及东亚季风指数序列周期接近,故用交叉小波分析发现广东旱涝指数序列与太阳黑子相对数序列在0~6 a、7~8 a和11~16 a等多个时间尺度具有强凝聚性共振周期,与东亚夏季风指数序列在4~8 a和25~45 a等多个时间尺度具有强凝聚性共振周期。 相似文献
12.
This paper investigates why some La Niña events are followed by another La Niña and some others are not. We propose two preconditions that result in continuation of a La Niña. The first one is that La Niña must be a strong event (a major La Niña). This ensures that the reflected Rossby wave signal at the eastern boundary of the Pacific has a strong westward propagating cold ocean temperature anomaly over the off-equatorial region. The off-equator cold anomaly may not be conducive to the equatorial recharge process, and as a result, may favor the persistence of cold ocean subsurface temperature anomaly and prevent the transition from La Niña to El Niño. The second precondition is whether there are eastward propagating downwelling Kelvin waves during the decay phase of a major La Niña. Eastward propagating downwelling Kelvin waves could lead to demise for a tendency for a follow-up La Niña. The equatorial Kelvin wave activities are associated with fluctuations of surface wind in the equatorial far-western Pacific. The analysis suggests that both the surface wind in the equatorial far-western Pacific and the recharge/discharge of the equatorial Pacific are indicators for occurrence or no occurrence of a follow-up La Niña event. 相似文献
13.
F. W. Dobson 《Boundary-Layer Meteorology》1971,1(4):399-410
The signals from a wave probe, a buoy-mounted sensor at the water surface, and a three-component sonic anemometer were recorded during the passage of a discrete group of waves which were travelling against a light wind. Cross spectra between the wave signals and the pressure and sonic anemometer signals were obtained and are interpreted.Bedford Institute contribution No. 226.This work forms part of a Ph.D. dissertation at the Institute of Oceanography, University of British Columbia. 相似文献
14.
A key question for climate mitigation and adaptation decisions is how quickly significant changes in temperature extremes will emerge as greenhouse gas concentrations increase, and whether that emergence will be uniform between hot and cold extremes and across different geographic areas. We use a high-resolution, multi-member ensemble climate model experiment over the United States (U.S.) to investigate the transient response of the annual frequency, duration and magnitude of 8 daily-scale extreme temperature indices during the twenty-first century of the A1B emissions scenario. We evaluate the time of emergence of a permanent exceedance (PE) above the colder part of the historical (1980–2009) extremes distribution, and the time of emergence of a new norm (NN) centered on the historical maxima (for hot extremes) or minima (for cold extremes). We find that during the twenty-first century, hot extremes permanently exceed the historical distribution’s colder half over large areas of the U.S., and that the hot extremes distribution also becomes centered on or above the historical distribution’s maxima. The changes are particularly robust for the exceedance of the annual 95th percentile of daily maximum temperature over the West and the Northeast (with the earliest emergence of a PE by 2030 and of a NN by 2040), for warm days over the Southwest (with the earliest emergence of a PE by 2020 and of a NN by 2030), and tropical nights over the eastern U.S. (with the earliest emergence of a PE by 2020 and of a NN by 2030). Conversely, no widespread emergence of a PE or a NN is found for most cold extremes. Exceptions include frost day frequency (with a widespread emergence of a PE below the historical median frequency by 2030 and of a NN by 2040 over the western U.S.), and cold night frequency (with an emergence of a PE below the historical median frequency by 2040 and of a NN by 2060 in virtually the entire U.S.). Our analysis implies a transition over the next half century to a climate of recently unprecedented heat stress in many parts of the U.S., along with cold extremes that, although less frequent, remain at times as long and as severe as are found in the current climate. 相似文献
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16.
We consider small non-divergent perturbations to a barotropic current flowing parallel to a straight coastline. Sufficient conditions for stability and a semi-circle theorem are established for general current profiles and topography. An asymptotic expansion for long waves is described. Some analytic solutions are obtained when the topography is piece-wise constant and the current is piece-wise linear. Two kinds of instability, a shear instability and a topographic instability, are identified. Our results are applied to a model of the East Australian current. 相似文献
17.
R. A. Brown 《Boundary-Layer Meteorology》1974,7(4):489-500
The relationship between geostrophic, Ekman-layer, and surface-layer flow is explored. Formalized limit solutions for each layer are developed; together they form a continuous solution for the semi-infinite flow over a surface. These classical solutions are re-derived and related, to prepare for a two-layer composite boundarylayer solution with patching criteria. The patching process yields a resistance law which indicates a correspondence between the stress and the geostrophic flow deviation involving a similarity relation with two arbitrary parameters. 相似文献
18.
“15.7”广西超长持续性暴雨过程多尺度特征分析 总被引：5，自引：1，他引：5
利用多源气象资料,通过综合诊断分析方法,对2015年一次广西持续性暴雨过程进行多尺度特征分析。(1) 南亚高压经历了双体型构建,副热带长波槽有利于冷空气南下和高空急流的建立。El Ni?o状态下,副高强度偏强,位置偏西、偏南,有利于暖湿气流向广西输送。南亚高压过渡层与副高对峙,有利于冷暖空气在广西交汇。(2) 影响天气系统有高空槽、切变线、冷锋、低空急流、季风槽及低涡等多天气系统。降雨分为锋前暖区、锋面、高空槽加强、季风槽与低涡等四个阶段。(3) 中尺度特征为锋前暴雨发生在MCC云团形成到减弱期,雷达强回波呈弓型,对流性强;锋面暴雨发生在MCC减弱后云带,雷达强回波为弓型向直线型转换,对流性减弱;高空槽加强暴雨为直线型云系和雷达回波增强;季风槽与低涡暴雨为增强的涡旋型云系和雷达强回波。(4) 暴雨发生在总体地势为云贵高原下坡和地面喇叭口地形辐合的桂西北、海陆分布差异的沿海及山脉迎风坡的桂东南。可见,长时间持续性暴雨过程是一个多尺度和多天气系统相互作用的结果,暴雨发生在有利的大尺度环流背景和天气系统配置下的中小尺度系统频繁发生处,地形助推暴雨作用明显。深刻理解持续性暴雨发生的尺度特征可提高该类天气预报能力。 相似文献
19.
Single-Column Model Intercomparison for a Stably Stratified Atmospheric Boundary Layer 总被引：2，自引：15，他引：2
J. Cuxart A. A. M. Holtslag R. J. Beare E. Bazile A. Beljaars A. Cheng L. Conangla M. Ek F. Freedman R. Hamdi A. Kerstein H. Kitagawa G. Lenderink D. Lewellen J. Mailhot T. Mauritsen V. Perov G. Schayes G-J. Steeneveld G. Svensson P. Taylor W. Weng S. Wunsch K-M. Xu 《Boundary-Layer Meteorology》2006,118(2):273-303
The parameterization of the stably stratified atmospheric boundary layer is a difficult issue, having a significant impact on medium-range weather forecasts and climate integrations. To pursue this further, a moderately stratified Arctic case is simulated by nineteen single-column turbulence schemes. Statistics from a large-eddy simulation intercomparison made for the same case by eleven different models are used as a guiding reference. The single-column parameterizations include research and operational schemes from major forecast and climate research centres. Results from first-order schemes, a large number of turbulence kinetic energy closures, and other models were used. There is a large spread in the results; in general, the operational schemes mix over a deeper layer than the research schemes, and the turbulence kinetic energy and other higher-order closures give results closer to the statistics obtained from the large-eddy simulations. The sensitivities of the schemes to the parameters of their turbulence closures are partially explored. 相似文献
20.
A numerical stochastic model is developed for the upcrossing rate across a specified threshold concentration. The model assumes that the concentration time series at a given spatial point within a dispersing plume can be approximated as a first-order Markovian process designed to be consistent with a given time-invariant concentration probability density function (pdf). The model requires only the specification of a concentration pdf with a given mean and variance and a concentration fluctuation integral time scale. Predicted upcrossing rates are compared with atmospheric plume concentration data obtained from a point source near the ground. For this data set, a log-normal pdf is found to give better estimates of the threshold crossing rate than a gamma pdf. 相似文献