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1.
为了建立沿海风功率预报系统，本文探讨了中国沿海风电场风速预报问题，并利用数值模式RAMS对海陆风进行了模拟研究.发现海陆风发生时，海风和陆风阶段风速廓线存在较大差异，海风阶段风速的垂直切变明显小于陆风阶段.海陆风发生时，风速会呈现有规律的变化，即海风和陆风分别有两个时段：风速增加时段和风速减少时段.在为沿海风电场提供风速预报时，当模式预报到海陆风发生时，可以利用海陆风的这种特点，使用统计方法对预报出的风速进行有效的订正.并发现即使没有海陆风发生，当风向为海洋吹向陆地时，风速随高度的垂直切变同样小于陆地吹向海洋的时段.利用统计方法根据不同风向时风速廓线的特性，把数值模式计算高度上的预报结果，精确地插值到风机涡轮高度，会很大程度上减少风速预报的误差及风功率预报环节的误差. 相似文献
2.
采用著名的Lorenz63模式,数值研究了常数型最优强迫在校正数值模式中的作用.结果表明,当数值模式仅考虑由于参数误差导致的随状态变量发展变化的模式误差时,在数值模式倾向方程叠加常数型最优强迫能够很好地抵消该类模式误差对预报结果的影响;当数值模式未考虑观测中依赖于时间的随机过程时,常数型最优强迫也可以较好地抵消由随机过程导致的模式误差的影响.实际情形中,数值模式预报结果同时受到由随机过程和参数不确定性导致的模式误差及其相互作用的影响.结果表明,常数型最优强迫方法同样能够在很大程度上抵消该类混合型模式误差对预报结果的影响.综上所述,即使模式物理过程产生的模式误差是依赖于时间变化的,在模式中叠加常数型最优强迫校正模式的方法也可以在很大程度上抵消模式误差对预报结果的影响.常数型最优强迫方法可能是一个较好的校正模式和改进模式预报技巧的方法. 相似文献
3.
我国是世界上受台风灾害影响最严重的国家之一.减轻台风灾害首先依赖于台风预报能力,这主要取决于台风数值预报模式及其关键技术的发展水平.本文简要回顾了国内台风数值预报模式的发展历程;介绍了目前国内模式在台风初始化和物理过程等方面的关键技术特点;分析了模式技术中存在的主要问题,并就今后的技术发展提出了建议.文中指出,一方面,尽管基于经验假设的涡旋构造技术在典型台风的分析和预报中仍发挥着重要作用,但为提高对异常台风路径和强度变化的预报,需要加强卫星等观测资料在模式分析中的应用.另一方面,通过加强模式细网格条件下的物理过程参数化研究,可以更加合理地刻画台风中小尺度物理过程,进一步提高台风强度、风雨预报性能. 相似文献
4.
针对延伸期尺度的可预报分量,借鉴了CNOP相关算法,形成了在数值模式中提取可预报分量的实用方法和预报技术.从模式预报误差增长的角度将模式变量分为可预报分量和不可预报的混沌分量,将可预报分量定义为在预报时段内误差增长较慢的分量.基于现有的国家气候中心月动力延伸预报业务模式,建立了针对可预报分量的数值模式.同时结合历史资料有用信息,对数值模式的可预报分量,在历史资料的可预报分量中寻找相似场,降低了相似判断过程中变量的维数,进一步对可预报分量的预报误差进行订正.对混沌分量利用历史资料,通过集合预报方法得出其期望值和方差.数值试验结果表明,该方法能有效提高10～30天延伸期数值模式大气环流场的预报技巧,具有良好的业务应用前景. 相似文献
5.
下击暴流风的数值仿真研究 总被引：1，自引：0，他引：1
作为自然界的一种强风荷载,雷暴天气产生的下击暴流风在世界范围内造成了大量工程结构物的破坏。研究证实,下击暴流风具有同常规的大气边界层近地风完全不同的风场特征。利用通用商业CFD(Computational fluid dynamics)软件FLUENT完成了几何缩尺比为1:2000的下击暴流过程的数值仿真。非定常的数值模拟将有助于更好地理解下击暴流风的动力特征。数值结果表明,基于雷诺平均的Navier-Stokes方程进行的非定常数值模拟结果同根据实测数据提出的三种经验风剖面吻合良好,在目前实测资料稀少的情况下,有助于更好地研究下击暴流风的基本特征。 相似文献
6.
全球非静力半隐式半拉格朗日模式及其极区离散处理 总被引：1，自引：0，他引：1
全球有限区同化预报系统GRAPES(Global Regional Assimilation and Prediction System)中的全球模式是新研发的新一代全球非静力数值预报模式, 该模式将作为中国气象局下一代全球中期数值预报的业务模式. 模式动力框架的特点包括采用全可压方程组、非静力/静力可选、半隐式半拉格朗日大时间步长、利用预条件求解复杂的三维亥姆赫兹(Helmholtz)椭圆型方程等. 针对极地奇异性的特点, 介绍了GRAPES全球模式在极地的离散处理方案, 包括采用水平风分量v放在极地的Arakawa C网格, 引入极地滤波解决极地数值计算的稳定性, 近极地Helmholtz方程的订正, 及为提高球坐标系下拉格朗日上游点计算精度的处理等. 平衡流理想场试验表明, 模式对极地半拉格朗日上游点及极地的处理是正确的; Held 和 Suarez试验表明模式可保证长期时间积分的守恒特性. 相似文献
7.
对区域土壤湿度预报结果的检验是评价数值模式预报效果、改进预报性能的重要环节.随着技术的发展,数值模式时空分辨率不断提高,然而土壤湿度区域预报检验采用的仍多为平均值或均方根误差等强度检验方法,不易完整和准确地了解模式的预报性能.SAL方法是针对降水预报设计的基于对象的区域检验方法,本文在SAL方法基础上,提出了一种可进行土壤湿度区域检验的新方法(SAL-DN).理想试验和真实试验均表明:SAL-DN方法能够从结构、强度和位置这三个方面检验土壤湿度区域预报和实测存在的差异,且检验结果较符合实际情况.此外,相比SAL方法,SAL-DN方法能够检验土壤湿度、气温等具有双类(高、低值)中心的物理量,有着广泛的应用前景. 相似文献
8.
动力相似预报的策略和方法研究 总被引：7，自引：0，他引：7
为了在现有模式和资料条件下有效提高数值预报水平, 深入开展了动力相似预报(DAP)的策略和方法研究. 提出“利用历史相似信息对模式预报误差进行预报”的新思路, 从而将动力预报问题转化为预报误差的估计问题, 并发展了一种基于相似误差订正的预测新方法(FACE). 进一步将FACE应用于业务海气耦合模式的跨季度预测试验, 夏季平均环流和降水的预测结果表 明, FACE能在一定程度上减小预报误差、恢复预报方差、提高预报技巧. 此外, 敏感性试验显示, 相似的个数、选取变量和度量标准都对FACE预报有显著影响. 相似文献
9.
延伸期可预报分量的预报方案和策略 总被引：2，自引：0，他引：2
延伸期时间尺度虽然超过逐日天气预报时效理论上限,但仍然存在可预报的气象场特征.本文针对延伸期尺度的可预报分量,提出了有针对性的预报方案和策略.基于大气系统的混沌特性,从误差增长的角度在数值模式中分离了可预报分量和不可预报的随机分量,将可预报分量定义为在预报时段内误差增长较慢的分量,它对初值小的误差不极其敏感.通过在预报过程中滤除随机分量,保留可预报性较高的分量,建立起针对可预报分量的数值模式,避免小尺度分量预报误差的快速增长对预报效果的影响.同时,结合历史资料,利用相似-动力方法对可预报分量的预报误差进行订正,达到减小模式误差和从统计角度考虑随机分量对可预报分量影响的目的.结果表明,该方法能有效提高数值模式对可预报分量的预报技巧,从空间分布上体现为对可预报性较高的地区改进更为明显;从空间尺度上看,改进最为明显的是0波,其次是超长波和天气尺度波,与各尺度的可预报性有很好的一致性.该方法能有效减小可预报分量的模式误差,提高预报技巧,显示出良好的业务应用前景. 相似文献
10.
析了2002年夏季上海GPS综合应用网（简称SGCAN）的观测数据,实时处理中直接利用IGS（International GPS Service）超快速产品IGU（the Ultrarapid orbit of IGS）轨道,在长基线辅助下考虑海潮的影响,得到了可靠的可降水汽量（简称PWV）序列,监测结果与加密的Radiosonde观测比较,偏差为2mm左右. 与MM5预报可降水量的比较说明GPS监测结果可以作为检验数值预报质量的工具之一. 2002年夏季SGCAN监测的PWV时空变化过程反映了长江三角洲地区从西南到东北的详细入梅雨过程和特点,以及整个梅雨季节雨带在江淮地区来回摆动的情况. 一小时雨量与GPS/PWV锋值的对应关系统计表明GPS/PWV对雷暴雨具有一定的短期预报特性. 利用Cressman分析方法把GPS/PWV插值到中尺度数值预报模式初始场的各个格点上,改进了数值预报初始湿度场的精度,提高了中尺度数值预报的准确性,反映了GPS/PWV促进雷暴雨数值预报能力的潜力. 相似文献
11.
Observations of currents aimed to study the flow near a spawning aggregation reef, Gladden Spit off the coast of Belize, reveal unusually strong currents on 19–20 October 2009 (the current speed was over 1?m?s?1, when the mean and standard deviation are 0.2?±?0.12?m?s?1). During this short time, the water level was raised by 60–70?cm above normal in one place, but lowered by 10–20?cm in another location just 2?km away. The temperature dropped by over 2°C within a few hours. Analyses of local and remote sensing data suggest that a rare combination of an offshore Caribbean cyclonic eddy, a short-lived local tropical storm, and a Spring tide, all occurred at the same time and creating a “perfect storm” condition that resulted in the unusual event. High-resolution simulations and momentum balance analysis demonstrate how the unique shape of the coral reef amplified the coastal current through nonlinear flow–topography interactions. The suggested mechanism for the water level change is different than the classical wind-driven storm surge process. The study has implications for the influence of external forcing on mixing processes and physical–biological interactions near coral reefs. 相似文献
12.
Rationalized by the observational circulation pattern in the upper ocean of the North Pacific, meridional friction term is
first incorporated in a barotropic theoretical model of the wind-driven circulation. The governing potential vorticity equation
thence has β term and wind stress curl term (the two of the Sverdrup balance), zonal friction term and meridional friction
term. The analytical solution satisfactorily captures many important features of the wind-driven circulation in the North
Pacific: Kuroshio, Oyashio, Kuroshio extension, North Equatorial Current, and especially the eastern boundary currents in
the North Pacific, i.e. California current and Alaska current. 相似文献
13.
Observations of turbulence avoidance in zooplankton are compared to estimates of the wind-driven turbulence in the upper ocean. Plankton that avoid wind-driven turbulence by moving deeper are no longer transported by the wind-driven Ekman currents near the surface because they are no longer near the surface. Here, a threshold level of turbulence that triggers an avoidance response is estimated, and is used to infer the wind speed and water column stratification conditions that would lead to zooplankton leaving the Ekman layer. Turbulence avoidance is argued to lead to near-shore retention in wind-driven upwelling systems, and to a reduction of the delivery of zooplankton to Georges Bank from the deeper waters of the Gulf of Maine. 相似文献
14.
The aim of this study is to investigate tide–surge interaction in narrow channels with complex and relatively shallow topography. A high-resolution depth-integrated tidal and storm surge model has been implemented for the Tjeldsund channel which is an important sailing lane in northern Norway. A horizontal grid resolution down to 50 m is applied in order to represent the complex bottom topography and the formation of jets and small-scale eddies. Two typically storm surge events in December 2004 have been examined in detail. The tide–surge interaction is found to influence the generation of higher harmonics and the formation of eddies in the current field. In some cases, the magnitude of storm surge currents may reach the same magnitude as the tidal currents enhancing the formation of jets and eddies. 相似文献
15.
深入认识大型湖泊在不同风速、风向和水位下三维风生流结构特征对于湖泊污染控制、生态恢复及资源的开发利用具有重要意义.本文在构建笛卡尔坐标系下洪泽湖三维水动力模型的基础上,利用2次全湖30个点位流场监测数据验证了模型精度.基于1975-2020年长系列风场观测数据,确定了洪泽湖典型风速风向.在此基础上,模拟了16种不同风向,13种不同风速和20种不同水位工况条件下洪泽湖三维风生流结构.结果表明：水动力模型可以较好地刻画洪泽湖三维湖流变化特征.洪泽湖风生流结构随风向变化呈现出较大空间差异.风生流流速随着风速的升高呈加速上升趋势,其中表层水体流速上升幅度远高于其他水层.在2.4 m/s东风驱动下,溧河洼、成子湖和南部湖区垂向平均流速随着水位上升呈先升高后降低的趋势,3个湖区分别在12.7、12.4和12.2 m水位下流速达到最大值. 相似文献
16.
The Pearl River Estuary (PRE) in South China's Guangdong Province is a subtropical estuary with highly irregular topography
and dynamically complicated circulations. A nested-grid coastal circulation modelling system is used in this study to examine
dynamic responses of the PRE to tides, meteorological forcing and buoyancy forcing. The nested-grid modelling system is based
on the Princeton Ocean Model and consists of three downscaling subcomponents: including an outer-most model with a coarse
horizontal resolution of ~7 km for simulating tidally forced and wind-driven surface elevations and depth-mean currents over
the China Seas from Bohai Sea to the northern South China Sea and an innermost model with a fine resolution of ~1.2 km for
simulating the 3D coastal circulation and hydrography over the PRE and adjacent coastal waters. Model results during the winter
northeast monsoon surge in January and super typhoon Koryn in June of 1993 are used to demonstrate that the 3D coastal circulation
and hydrographic distributions in the PRE are affected by tides, winds and buoyancy forcing associated with river discharge
from the Pearl River with significant seasonal and synoptic variabilities. 相似文献
17.
Across-slope bottom boundary layer (BBL) fluxes on the shelf-edge connect this region to deeper waters. Two proposed ways in which across-slope BBL fluxes can occur, in regions that have a slope current aligned to the bathymetry, are the frictional veering of bottom currents termed the ‘Ekman drain’ and through local wind-forced downwelling (wind-driven surface Ekman flow with an associated bottom flow). We investigate the variability, magnitude and spatial scale of BBL fluxes on the Shetland shelf, which has a prominent slope current, using a high-resolution (～2 km) configuration of the MITgcm model. Fluxes are analysed in the BBL at the shelf break near the 200 m isobath and are found to have a seasonal variability with high/low volume transport in winter/summer respectively. By using a multivariate regression approach, we find that the locally wind-driven Ekman transport plays no explicit role in explaining daily bottom fluxes. We can better explain the variability of the across-slope BBL flux as a linear function of the speed and across-slope component of the interior flow, corresponding to an Ekman plus mean-flow flux. We estimate that the mean-flow is a greater contributor than the Ekman flux to the BBL flux. The spatial heterogeneity of the BBL fluxes can be attributed to the mean-flow, which has a much shorter decorrelation length compared to the Ekman flux. We conclude that both the speed and direction of the interior current determines the daily BBL flux. The wind does not explicitly contribute through local downwelling, but may influence the interior current and therefore implicitly the BBL fluxes on longer timescales. 相似文献
18.
Interaction of a river plume with coastal upwelling in the northeastern South China Sea 总被引：5，自引：0，他引：5
Observational and modeling studies were conducted to investigate the Pearl River plume and its interaction with the southwesterly driven upwelling circulation in the northern South China Sea during the summer. After exiting the Pearl River Estuary, the discharged freshwater generates a nearly stationary bulge of freshwater near the entrance of the estuary. Forced by the wind-driven coastal upwelling current, the freshwater in the outer part of the bulge flows downstream at the speed of the current and forms a widening and deepening buoyant plume over the shelf. The plume axis gradually shifts offshore of the current maximum as a result of currents induced by the contrasting density at the nose of plume and by the intensified Ekman drift in the plume. In this plume–current system, the fraction of the discharged freshwater volume accumulated in the bulge reaches a steady state and the volume of newly discharged freshwater is transported downstream by the upwelling current. Enhancement of stratification by the plume thins the surface frictional layer and enhances the cross-shelf circulation in the upper water column such that the surface Ekman current and compensating flow beneath the plume are amplified while the shoaling of the deeper dense water in the upwelling region changes minimally. The pressure gradient generated between the buoyant plume and ambient seawater accelerates the wind-driven current along the inshore edge of the plume but retards it along the offshore edge. Along the plume, downward momentum advection is strong near the highly nonlinear source region and a weaker upward momentum advection occurs in the far field over the shelf. Typically, the plume is shaped by the current over the shelf while the current itself is adjusting to a new dynamic balance invoked by the plume-induced changes of vertical viscosity and the horizontal pressure gradient. The spatial variation of this new balance leads to a coherent change in the cross-isobath transport in the upper water column during upwelling. 相似文献
19.
The effects of wave–current interactions on ocean surface waves induced by Hurricane Hugo in and around the Charleston Harbor and its adjacent coastal waters are examined by using a three-dimensional (3D) wave–current coupled modeling system. The 3D storm surge modeling component of the coupled system is based on the Princeton Ocean Model (POM), the wave modeling component is based on the third generation wave model, Simulating WAves Nearshore (SWAN), and the inundation model is adopted from [Xie, L., Pietrafesa, L. J., Peng, M., 2004. Incorporation of a mass-conserving inundation scheme into a three-dimensional storm surge model. J. Coastal Res., 20, 1209–1223]. The results indicate that the change of water level associated with the storm surge is the primary cause for wave height changes due to wave–surge interaction. Meanwhile, waves propagating on top of surge cause a feedback effect on the surge height by modulating the surface wind stress and bottom stress. This effect is significant in shallow coastal waters, but relatively small in offshore deep waters. The influence of wave–current interaction on wave propagation is relatively insignificant, since waves generally propagate in the direction of the surface currents driven by winds. Wave–current interactions also affect the surface waves as a result of inundation and drying induced by the storm. Waves break as waters retreat in regions of drying, whereas waves are generated in flooded regions where no waves would have occurred without the flood water. 相似文献
20.
The irregularity velocity patterns observed by the SABRE coherent radar at substorm expansion phase onset, which is identified by magnetometer observations of Pi2 pulsations, are occasionally highly structured. In all the examples of structured velocity patterns examined, the SABRE viewing area is located at longitudes within the inferred substorm current wedge. Three types of structured velocity regime are apparent depending on the level of magnetic activity and the position of the radar viewing area relative to the substorm enhanced currents and the Pi2 pulsation generation region. Firstly, vortex-like velocity patterns are observed and these may be caused by the field-aligned currents associated with the substorm current wedge. Secondly, regions of equatorward velocity are also observed at times of substorm expansion phase onset moving longitudinally across the SABRE viewing area. The longitudinal movement is usually westward although an example of eastward motion has been observed. The phase velocity of these regions of equatorward flow is typically 1–3 km s?1. The observed equatorward velocities occur at the poleward edge or poleward of the background convection velocities observed by SABRE. These equatorward velocities may be related to the westward travelling surge and to the expansion (eastwards as well as westwards) of the brightening arc region at substorm onset. Thirdly, the flow rotates equatorward within the field of view but does not then appear to move longitudinally. These equatorward velocities may relate to the earthward surge of plasma from the magnetotail at substorm onset. 相似文献