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1.
Parameterization of the thermal impacts of sub-grid orography on numerical modeling of the surface energy budget over East Asia 总被引：4，自引：0，他引：4
Summary A parameterization scheme for the thermal effects of subgrid scale orography is incorporated into a regional climate model
(developed at Nanjing University) and its impact on modeling of the surface energy budget over East Asia is evaluated. This
scheme includes the effect of terrain slope and orientation on the computation of solar and infrared radiation fluxes at the
surface, as well as the surface sensible and latent heat fluxes. Calculations show that subgrid terrain parameters alter the
diurnal cycle and horizontal distributions of surface energy budget components. This effect becomes more significant with
increased terrain slope, especially in winter. Due to the inclusion of the subgrid topography, the surface area of a model
grid box changes over complex terrain areas. Numerical experiments, with and without the subgrid scale topography scheme,
show that the parameterization scheme of subgrid scale topography modifies the distribution of the surface energy budget and
surface temperature around the Tibetan Plateau. Comparisons with observations indicate that the subgrid topography scheme,
implemented in the climate model, reproduces the observed detailed spatial temperature structures at the eastern edge of the
Tibetan Plateau and reduces the tendency to overestimate precipitation along the southern coastal areas of China in summer. 相似文献
2.
用NCAR区域气候模式(RegCM2)的数值试验，研究了包络地形和地形重力波拖曳作用对1991年5、6月份中国区域内气候模拟效果的影响。通过试验结果的对比分析发现，在模式中引入地形重力波拖曳作用可在一定程度上改善模式对气候系统和要素的模拟效果，使模拟结果更符合气候实况。包络地形对模拟结果也有一定的改善，但对于细网格的区域气候模式(RCM)来说，其效果不如重力波拖曳明显。不论是地形重力波拖曳还是包络地形，在模式积分的初期，它们的作用并不明显，随着积分时间的增长，它们对模拟结果的影响程度增大。 相似文献
3.
青藏高原绕流和爬流的气候学特征 总被引：2，自引：2，他引：0
本文利用1951～2008 年NCEP/NCAR 再分析资料, 通过绕流和爬流方程, 将高原附近表层风场分解为绕流分量和爬流分量两部分, 计算出了实际大气中的绕流和爬流运动的强度, 分别探讨它们的气候态特征。结果表明:高原主体年平均绕流场围绕高原地形并在高原西南部(32°N, 75°E)附近产生分支, 分支点下游的高原主体南部和北部分别表现为气旋性和反气旋性流型;年平均的爬流分量场沿喜马拉雅山脉辐散, 高原主体为偏南上坡风, 东北部为偏北上坡风。夏季绕流场为气旋式流型, 中心位于高原中部(35°N, 90°E)附近;秋季绕流场围绕高原地形边缘基本为一个反气旋流型。夏季, 高原主体偏南风爬流与偏北风爬流在高原南北中线附近辐合, 除夏季外, 沿高原南侧喜马拉雅山脉为爬流辐散区。高原主体和高原附近的关键区内, 绕流和爬流存在不同的季节循环特征。从绕流和爬流分解公式出发, 本文详细探讨了表面流场的绕流和爬流运动各分量对地形高度及地形梯度的依赖性:经向绕流与纬向绕流比值、经向爬流与纬向爬流分量比值为仅依赖于地形高度的定常值。年平均的绕流及爬流矢量强度随着所处地形高度的升高而逐步增强;从区域分布的角度而言, 高原附近绕流强于爬流的区域范围较广, 绕流占主导地位。地形纯动力强迫产生的爬流运动与观测资料中高原附近的垂直运动具有很高的位置对应关系, 但冬季和夏季均存在强度上的差异。 相似文献
4.
In order to investigate the impact of the smoothed orography and the spurious orographic ripples on simu-lations in the low-resolution spectral model, three different numerical tests, that is, the unsmoothed orography scheme, the smoothed orography scheme and non-ripples scheme are performed. In this paper, the model used by us is the same as Part I except for orographic specification.The results from simulations indicate that, as far as the climatic simulation is concerned, some aspects of the simulated stationary disturbances, zonal and meridional wind, temperature and precipitation in the low-resolu-tion spectral model with properly smoothed mountains are significantly improved, especially in winter hemis-phere.The deep ripples in the model with the unsmoothed orography produce spurious high pressure regions at the surface with subsidence, and suppress rainfall, causing an unrealistic splitting of the precipitation area in northern winter and summer. Removal of tbe deep ripples by using the special procedure for smoothing topog-raphy allows a strong upward motion in the ripple area with heavy rainfall, eliminating the unrelistic split in the precipitation area. 相似文献
5.
Martina Tudor 《Meteorology and Atmospheric Physics》2010,108(1-2):57-70
Fog and low stratus forecasting experiments have been carried out with the numerical weather prediction model ALADIN on a case of long lasting fog. The model has been used with different radiation, cloud diagnosing and horizontal diffusion schemes, different representation of orography, increased vertical resolution and with or without prognostic condensates and turbulent kinetic energy (TKE). Some of the numerical set-ups are able to reproduce the fog (low stratus) field as seen in the satellite images as well as the measured 2m temperature and relative humidity diurnal cycles. The results show that cloud diagnosing schemes and overlap assumptions play a more important role than a more sophisticated radiation scheme, or introduction of prognostic cloud water, ice, rain, snow or TKE. More realistic orography representation and a more physical horizontal diffusion scheme significantly improve the modelled low stratus and 2m temperature in the areas with variable orography. 相似文献
6.
Summary The problem of representing the drag due to subgridscale orography is examined. Results from model simulations are used to illustrate clear deficiencies in the global angular momentum budgets and possible ways of correcting for these deficiencies are considered. It is argued that a formulation for the stress due to subgridscale gravity waves is required, as was first recognized by Boer et al. (1984a, b), and the impact of a scheme based on Palmer et al. (1986) is presented. The scheme is improved by using directionally-dependent subgridscale orographic variances. Results from 90-day integrations using the ECMWF and UKMO models with similar resolutions are very much in accord both with and without a wave drag parametrization scheme; showing much improved wintertime circulations.The relationship between the wave drag and the model orography is examined with the use of idealized stress profiles whereby the wave drag is limited to either near the surface or in the stratosphere. A combination of parametrized wave drag with an envelope orography performs best at this stage of development.Results are presented from a substantial series of ten-day forecast experiments with the ECMWF operational model using mean and (1 ) envelope orographies, these show significant improvements in forecast skill.With 26 Figures 相似文献
7.
In order to identify the sensitivity of the numerical simulation to the orography specification in a low resolution spectral
model, two sets of numerical experiments for full-mountain and no-mountain cases are performed. By comparing the results,
it is possible to determine the eflects of mountains on the atmospheric general circulation.
This is a global, spectral model incorporating the primitive equations sugmented by physical parameterization and mountains,
with five equally-spaced sigma levels in the vertical ang a triangular truncation at wavenumber 10 in the horizontal.
Analysis of results supports earlier work by demonstrating that the low resolution global spectral model is capable of simulating
the major features of global general circulation and indicates that it is necessary to consider the effects of mouniains on
stationary disturbances in the numerical simulation. The simulations show that topography plays an important role in intensifying
heat sources for maintenance of disturbances.
All the simulation tests indicate that orography has an important infiuence on the distribution of heat sources and sinks.
It reflects that interaction and interrelation exist between the effects of orography and heat sources and the atmospheric
circulhtion via the dynamical processes of atmosphere. This result confirms the view points proposed by Yeh and Zhu (1958),
but differs from those by Kasahara and Washington (1971), Manabe and Terpstra (1974). 相似文献
8.
大尺度山地上空的臭氧低值及地面加热 总被引：11，自引：0，他引：11
首次利用Ｎｉｍｂｕｓ－７卫星上搭载的臭氧观测光谱仪（ＴＯＭＳ）资料,分析研究了大尺度山地（青藏高原、洛基山脉和安第斯山脉）上空臭氧总量的分布和季节变化规律,指出了大尺度山地对大气臭氧的减少作用。从全球大气臭氧总量分布和纬向偏差分布可以看出：在上述３个大尺度山地上空均存在着明显的臭氧低值扰动,该扰动区夏季强于冬季。在这３个区域中,青藏高原上空的臭氧低值扰动为最强。分析同时指出：上述大尺度山地上空臭氧季节变化的极小值在秋季,极大值在春季。但上述地区臭氧总量与同纬度其它地区臭氧总量的偏差在春季或初夏达到极小值。为分析这种大尺度山地对臭氧减少作用的原因,本文分析了青藏高原地面热源与臭氧总量的关系,指出：大尺度山地表面对大气的加热与该地区臭氧减少之间存在着良好的反相关;在地面对大气的感热加热、潜热加热和有效长波辐射加热中,以感热加热与臭氧减少的关系为最好。 相似文献
9.
Impacts of the thermal effects of sub-grid orography on the heavy rainfall events along the Yangtze River Valley in 1991 总被引：1，自引：1，他引：0
A P - σ regional climate model using a parameterization scheme to account for the thermal effects of the sub-grid scale orography was used to simulate the three heavy rainfall events that occurred within the Yangtze River Valley during the mei-yu period of 1991. The simulation results showed that by considering the sub-grid scale topography scheme, one can significantly improve the performance of the model for simulating the rainfall distribution and intensity during these three heavy rainfall events, most especially the second and third. It was also discovered that the rainfall was mainly due to convective precipitation. The comparison between experiments, either with and without the sub-grid scale topography scheme, showed that the model using the scheme reproduced the convergence intensity and distribution at the 850 hPa level and the ascending motion and moisture convergence center located at 500 hPa over the Yangtze River valley. However, some deviations still exist in the simulation of the atmospheric moisture content, the convergence distribution and the moisture transportation route, which mainly result in lower simulated precipitation levels. Further analysis of the simulation results demonstrated that the sub-grid topography scheme modified the distribution of the surface energy budget components, especially at the south and southwest edges of the Tibetan Plateau, leading to the development and eastward propagation of the negative geopotential height difference and positive temperature-lapse rate difference at 700 hPa, which possibly led to an improved precipitation simulation over eastern China. 相似文献
10.
In order to identify the sensitivity of the numerical simulation to the orography specification in a low resolution spectral model, two sets of numerical experiments for full-mountain and no-mountain cases are performed. By comparing the results, it is possible to determine the eflects of mountains on the atmospheric general circulation.This is a global, spectral model incorporating the primitive equations sugmented by physical parameterization and mountains, with five equally-spaced sigma levels in the vertical ang a triangular truncation at wavenum-ber 10 in the horizontal.Analysis of results supports earlier work by demonstrating that the low resolution global spectral model is capable of simulating the major features of global general circulation and indicates that it is necessary to consider the effects of mountains on stationary disturbances in the numerical simulation. The simulations show that topography plays an important role in intensifying heat sources for maintenance of disturbances.All the 相似文献
11.
该文用Nju-PσM的数值试验, 研究了包络地形和地形重力波拖曳作用对7月气候模拟效果的影响.通过试验结果的对比分析, 发现包络地形和重力波拖曳作用都可在一定程度上改善模式的模拟性能, 使模拟结果更符合气候实况. 相似文献
12.
地形和热源对冬季定常行星波形成的影响 总被引：2，自引：1，他引：2
本文用二层非线性原始方程谱模式，并在方程中考虑了Rayleigh摩擦、Newton冷却和温度水平扩散，在伟向均匀的初始场下，积分４０天，分别模拟了地形、热源单独作用和共同作用对冬季定常行星波形成的影响，尤其考虑了不同尺度地形和非定常热源的影响。 相似文献
13.
Asynchronous responses of East Asian and Indian summer monsoons to mountain uplift shown by regional climate modelling experiments 总被引：1，自引：1，他引：0
Hui Tang Arne Micheels Jussi T. Eronen Bodo Ahrens Mikael Fortelius 《Climate Dynamics》2013,40(5-6):1531-1549
It has been demonstrated in climate models that both the Indian and East Asian summer monsoons (ISM and EASM) are strengthened by the uplift of the entire Asian orography or Tibetan Plateau (TP) (i.e. bulk mountain uplift). Such an effect is widely perceived as the major mechanism contributing to the evolution of Asian summer monsoons in the Neogene. However, geological evidence suggests more diachronous growth of the Asian orography (i.e. regional mountain uplift) than bulk mountain uplift. This demands a re-evaluation of the relation between mountain uplift and the Asian monsoon in the geological periods. In this study, sensitivity experiments considering the diachronous growth of different parts of the Asian orography are performed using the regional climate model COSMO-CLM to investigate their effects on the Asian summer monsoons. The results show that, different from the bulk mountain uplift, the regional mountain uplift can lead to an asynchronous development of the ISM and EASM. While the ISM is primarily intensified by the thermal insulation (mechanical blocking) effect of the southern TP (Zagros Mountains), the EASM is mainly enhanced by the surface sensible heating of the central, northern and eastern TP. Such elevated surface heating can induce a low-level cyclonic anomaly around the TP that reduces the ISM by suppressing the lower tropospheric monsoon vorticity, but promotes the EASM by strengthening the warm advection from the south of the TP that sustains the monsoon convection. Our findings provide new insights to the evolution of the Asian summer monsoons and their interaction with the tectonic changes in the Neogene. 相似文献
14.
Summary A methodology developed for automatic classification of Objective Synoptic Processes (OSP) and its application to the study
of the mesoscale atmospheric circulatory patterns associated with them is described. The classification was based on the analysis
of the evolution of surface pressure and geopotencial height at 500 hPa during three days. An iterative procedure results
in an objective grouping of the main configurations describing different large-scale situations. This routine has been applied
over an appropriate domain covering the Iberian Peninsula to obtain OSPs in the region for the two month period July–August,
using daily synoptic maps for years 1990 to 1999 (a total of 7304 surface and 500 hPa synoptic maps have been used in the
analysis). Finally, for a characteristic day for two of the OSPs obtained, a mesoscale meteorological model (TAPM) has been
run at high resolution for the region of Catalonia, Northeastern Spain, in order to describe the local atmospheric circulatory
patterns associated with a given large-scale situation. Results show that the complex orography modifies the large-scale forcings
resulting in wind fields with a very important horizontal variability, significant daily cycle, and specific local features
related to orographic elements, which the model was able to incorporate due to the highly-resolved orography used. 相似文献
15.
16.
对1991年全球越赤道气流的分析和数值模拟 总被引：1，自引：0，他引：1
利用1991年国家气象中心全年分析资料,对全球各层（50～1000 hPa）越赤道气流（CEF）进行了分析。指出:主要季风区和1979年的相同,但在南美北部为弱季风区,而1979年为信风区。除南美北部外,主要信风区与1979年相同。还比较了这两类地区的特点,特别是非绝热加热分布随季节变化的特点,还用T21L5模式进行了数值模拟。结果表明:考虑地形和加热的方案最优,除个别情况外,CEF与实况很接近; 单纯加热方案次之,能定性地模拟CEF沿赤道的分布,但强度相差较大; 单纯地形方案最差。为了进行解释,还作了简单情况的理论分析。分析显示:考虑加热和地形作用,并不等于单纯地形和单纯加热的叠加,其间有非线性作用; 而且,这种非线性作用对CEF的产生是直接的、重要的; 单纯加热只有通过其对地面气压场的影响才能产生CEF。 相似文献
17.
利用考虑地形和水平扩散作用的正压涡度方程,在线性情况下,给出了描写对称运动和反对称运动(都是对赤道来说的)的方程和它们各自的解析解。分析这些解可以看出,不论对于对称运动或反对称运动,解都由三部份组成:一是与初始流场有关的Rossby波;一是以Rossby波波速传播的,与地形和水平扩散有关的行进波;另一是与地形和水平扩散有关的定常波。但是,如初始时刻运动是对称的,则地面拔海高度和水平扩散系数的反对称分布可以引起反对称运动,从而,引起非对称的运动。在定常情况下,则对称的流场,和地面拔海高度、水平扩散系数的对称分布有关,反对称的流场,和地面拔海高度、水平扩散系数的反对称分布有关。最后,还用数值试验,证明反对称地形可以引起反对称运动;还讨论了南北半球的相互影响的问题。 相似文献
18.
复杂地形区域风场模拟的准确率一直是风能研究领域的难点和重点。WRF模式是目前风能评估领域应用最广泛的天气数值模式之一,但该模式在复杂地形区域存在对平原、山谷风速高估且对山顶风速低估的系统性误差,并有研究建立次网格地形方案以订正误差。而次网格地形方案在不同水平分辨率下常出现错误的修正结果,该文基于高精度地形高程数据分析了方案失效的主要原因,发现其方程组中判断山体形态特征的阈值-20在过低和过高水平分辨率下均失去参考性。针对这一原因,将方案中影响关键参数Ct的地形高度算子与模式水平分辨率进行拟合,形成地形高度算子与水平分辨率相依赖的线性关系,获得不同分辨率下更适合的山体形态阈值。通过与自动气象站10 m风速对比分析了修正前后WRF对低层风速的模拟效果,结果显示:修正后的次网格地形方案能够分别在较低和较高分辨率下,部分矫正原方案错误的订正结果,使低层风速模拟更接近实况。修正后的次网格地形方案可为复杂地形区域开展高分辨率风场模拟提供参考。 相似文献
19.
EFFECTS OF OROGRAPHY AND HORIZONTAL DIFFUSION ON THE GENERATION OF THE ASYMMETRIC MOTION IN THE BAROTROPIC FILTERED MODEL ATMOSPHERE 
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下载免费PDF全文 By utilizing the barotropic vorticity equation including effects of orography and horizontal diffusion,the linearized equations describing symmetric and antisymmetric motions and their analytic solutions are pre-sented.It can be found from the solutions that no matter what kind of motion may be,each solution consistsof three waves,namely,Rossby wave related to initial values,marching wave propagating at Rossby wavevelocity and stationary wave.The latter two are closely related to orography and horizontal diffusion.However,if the motion is symmetric at the initial instant,then the antisymmetric components of orographyand of horizontal diffusion are likely to lead to the generation of antisymmetric motion.In the steady state,the symmetric flow is connected with symmetric orography and horizontal diffusion and the antisymmetricflow with antisymmetric orography and horizontal diffusion.Further,in order to verify the above analysis,three numerical experiments have been made.The results show that antisymmetric orography can produceantisymmetric motion.Finally,the atmospheric interactions between Northern and Southern Hemispheresare discussed. 相似文献