共查询到18条相似文献，搜索用时 125 毫秒
1.
两步保形平流方案在高分辨率球面经纬网格下的跳点差分试验 总被引：1，自引：0，他引：1
尝试用一个基于有限差分的两步保形平流方案（TSPAS）替代美国国家大气研究中心第5版公用大气模式（NCAR-CAM5）欧拉-谱动力框架中的半拉格朗日传输（SLT）平流方案,并针对不同分辨率版本,计算水汽等物质的传输过程。通过设计保证守恒性的跳点差分法,解决了基于经纬网格的模式在高分辨率下由于极区纬向格距过小而造成的差分方案积分时间步长过短的问题,使得TSPAS在高分辨率下仍然可以使用较大的时间步长。理想试验表明：（1）跳点TSPAS在守恒性、数值精度（量级上）、保形性等方面均较好地保持了原TSPAS的特点,而积分步长可增大到与CAM5-SLT相同,比原TSPAS提高超过一个数量级;（2）较半拉格朗日传输方案,尽管TSPAS的耗散更大,但是在相同时间步长下更省时,且改进了半拉格朗日传输求解平流方程造成的不守恒问题。CAM5的比较试验表明：（1）采用跳点TSPAS的模式结果与非跳点计算结果相当,在高纬度跳点区域也并未出现模拟异常;（2）在高分辨率下,采用跳点TSPAS方案的CAM5模拟结果与原模式结果相近,并初步显示对东亚青藏高原南侧的虚假降水有所抑制。该工作确保了基于欧拉通量差分型的TSPAS在高分辨率模式下的大时间步长稳定积分,为解决有限差分方法在高分辨率模式发展中的相关计算问题提供了启示,为后续针对东亚地区的模式性能改进奠定了基础。 相似文献
2.
本文提出一种将浅水波方程分裂为半拉格朗日平流项处理和适应项作隐式欧拉跳点差分格式(Eulerianalternating direction implicit)处理的积分方法。这种方法比半隐式方法简单,只需要给出线性三角方程(lineartridiagonal systems of equations)的解而不是赫姆霍尔兹方程的解就可以了。此方案理论上的性质已在E型格点上得到检验,对平流和简单罗斯贝(Rossby)渡是无条件稳定的,且有可以容忍的重力惯性设的稳定判据。通过采用两个时间层次积分方法给出了这两种波型二阶精度的解,并且不产生由分裂法引起的误差。将此方法用于有限区域正压模式,进行24小时的实例预报,其结果比Bates和McDonald以前提出的半拉格朗日方法更有效。 相似文献
3.
数值预报产品系统性误差的客观订正 总被引：5，自引：0，他引：5
从评价Ｔ４２数值预报模式的性能出发，找出Ｔ４２系统性误差的特征及其订正的客观判据。高度场Ｈ和温度场Ｔ采用不同时间权重和空莘平滑的订正方案，风场ｕ，ｖ采用动力订正方案，湿度场Ｑ采用平流（风场）订正方案。并对Ｔ４２１９９２年４－５月的数值预报产品进行了客观订正，经过均方根误差缩减率η和误差比ｅ方案的检验，效果是令人满意的。 相似文献
4.
《高原气象》2017,(4)
三次样条函数(样条格式)为二阶可导非线性格式,但样条格式线性部分是二阶导数中央差。本文在简谐波真解条件下,推导证明二阶导数中央差比一阶导数中央差的空间截断误差以及相速和群速误差均减少一倍。借鉴谱模式动力框架核心思想,高斯网格二维谱变换半隐式-半拉格朗日积分方案,研究准均匀经纬网格样条格式变换显式-准拉格朗日积分方案。引入原始大气运动方程,推导样条格式二阶时空离散准拉格朗日预报方程通式,得出静力守恒气压、气温预报方程,在经纬网格基础上,设计两种基本准均匀经纬网格,通过对压、温、湿、风及广义牛顿力(加速度)场做"经纬网格-准均匀经纬网格"三次样条函数变换,求得"水平双三次曲面+垂直三次样条"拟合上游点三次运动路径,用"匀加速"变率预报风场,进而求得一个时间步长平均"静力平流"三维位移散度场,并用它预报气压场增压和气温场绝热增温,从而实现全球静力质量守恒经纬网格三次样条函数变换显式-准拉格朗日积分方案,经初步积分试验,证明上述动力框架是可行的。 相似文献
5.
设计了IAP (InstituteofAtmosphericPhysics,ChineseAcademyofSciences)AGCM III,对其动力框架作说明和检验 ,时间积分采用改进的非线性迭代法。用Rossby Haurwitz波对框架进行了波型检验、能量检验和波速检验。结果表明 ,非线性迭代 3次的时间积分方案具有较好的稳定性 ,能够有效地抑制短波 ,同时对长波的歪曲较小 ,且时间积分步长可放得较大 ;该框架能够较长时间地保持Rossby Haurwitz 4波波型 ,在积分过程中能够较高精度地保持总有效能量守恒 ;模式计算的Rossby Haurwitz波速为每天西传 1 5个经度 ,这与理伦值很接近。 相似文献
6.
21层大气环流模式IAP AGCM-Ⅲ的设计及气候数值模拟Ⅰ.动力框架 总被引：4，自引：1，他引：3
设计了IAP(Institute of Atmospheric Physics, Chinese Academy of Sciences) AGCM-III,对其动力框架作说明和检验,时间积分采用改进的非线性迭代法.用Rossby-Haurwitz 波对框架进行了波型检验、能量检验和波速检验.结果表明,非线性迭代3次的时间积分方案具有较好的稳定性,能够有效地抑制短波,同时对长波的歪曲较小,且时间积分步长可放得较大;该框架能够较长时间地保持Rossby-Haurwitz 4波波型,在积分过程中能够较高精度地保持总有效能量守恒;模式计算的Rossby-Haurwitz波速为每天西传15个经度,这与理伦值很接近. 相似文献
7.
8.
《湖北气象》2016,(6)
研究经纬网格三次样条函数(样条格式)变换准拉格朗日平流方案,推导给出样条格式准拉格朗日预报方程通式,设计一种准均匀经纬网格,对气压、气温、风及广义牛顿力(加速度)场做"经纬网格-准均匀经纬网格"双三次曲面拟合,实现各个变量场在球面上的二阶可导,从而显式迭代插值求得上游点路径与预报变量值,上游点气块被限定在具备样条格式的斜率、曲率和挠率之变量场上运动。为验证样条格式求经纬网格上游点的可行性,采用了国际上通行、有效的一套理想场试验方案:平衡流试验、过极地气流试验和Rossby-Haurwitz波试验,用以检验经纬网格样条格式准拉格朗日平流方案的可行性、一致性、精确性及程序正确性。理想场试验表明,样条格式求上游点预报误差来源于三次样条函数"2阶空间余差"数学误差和上游点路径达不到精确轨迹的截断误差,其累积(积分)误差使得波动振幅变平,而波动位相传播无误差,且误差具有收敛性、球面对称性和单调有界性,同时证明,三次样条函数变换能够解决极区经纬网格点过密和极点奇异的经典问题。 相似文献
9.
为改善球面经纬度网格在高分辨率应用的苛刻限制,提高全球大气动力模式的时间积分效率,选取以阴阳网格为基础构建通量型非静力大气模式动力框架,采用有限体积法和通量型平流显式算法积分方案,保证模式的守恒计算性能。该动力框架在标准三维大气理想试验中进行了中期积分试验,对动力框架的计算效果、性能进行检验。在三维平衡流试验,罗斯贝-豪威茨波试验和山脉罗斯贝波试验中均表现出很好的稳定性和三维计算效果,其中水平2.5°分辨率模式的平衡流垂直速度误差为10-5量级,而经向速度误差在10-2量级,罗斯贝-豪威茨波保持基本波形稳定传播,而地形罗斯贝波试验则给出背风坡激发低槽在发展过程中不断向下游和南半球传播。 相似文献
10.
通过构建C网格的p-σ九层区域气候模式的差分方案,将C型跳点网格引入p-σ九层区域气候模式.通过对东亚地区1月和7月气候平均场及2003年夏季降水进行数值模拟,检验了C型跳点网格对p-σ九层区域气候模式模拟性能的影响.数值试验结果表明,C型跳点网格的p-σ九层区域气候模式对东亚区域气候的模拟能力有一定的提高,其中包括对流层低层风场和气温场的模拟都有了一定程度的改进,对风场的改进尤为明显.由于风场得到了改进,进而对降水的模拟能力也有所提高,为区域气候模式的进一步发展奠定了基础. 相似文献
11.
With the development of numerical weather prediction technology,the traditional global hydrostatic models used in many countries of the world for operational weather forecasting and numerical simulations of general circulation have become more and more unfit for high-impact weather prediction.To address this,it is important to invest in the development of global nonhydrostatic models.Few existing nonhydrostatic global models use consistently the grid finite difference scheme for the primitive equations of dynamical cores,which can subsequently degrade the accuracy of the calculations.A new nonhydrostatic global spectral model,which utilizes the Eulerian spectral method,is developed here from NCAR Community Atmosphere Model 3.0(CAM3.0).Using Janjic's hydrostatic/nonhydrostatic method,a global nonhydrostatic spectral method for the primitive equations has been formulated and developed.In order to retain the integrity of the nonhydrostatic equations,the atmospheric curvature correction and eccentricity correction are considered. In this paper,the Held-Suarez idealized test and an idealized baroclinic wave test are first carried out,which shows that the nonhydrostatic global spectral model has similar climate states to the results of many other global models for long-term idealized integration,as well as better simulation ability for short-term idealized integration.Then,a real case experiment is conducted using the new dynamical core with the full physical parameterizations of subgrid-scale physical processes.The 10-day numerical integration indicates a decrease in systematic error and a better simulation of zonal wind,temperature,and 500-hPa height. 相似文献
12.
The Dynamical and Climate Tests of an Atmospheric General Circulation Model Using the Second-Order
Adams-Bashforth Method 
下载免费PDF全文
下载免费PDF全文 The Asselin-Robert time filter used in the leapfrog scheme can degrade the accuracy of calculations. The second-order Adams-Bashforth method with the same accuracy as the leapfrog scheme is not subject to time splitting instability. A new semi-implicit atmospheric general circulation spectral model is developed on the basis of NCAR (National Center for Atmospheric Research) CAM3.0 (Community Atmosphere Model3.0). In this new model, the second-order Adams-Bashforth method is used as an alternative to the leapfrog scheme, and a Crank-Nicholson scheme is incorporated for the treatment of fast gravity modes. In this paper, the new model is tested by the Held-Suarez test and an idealized baroclinic wave test. Results of the Held-Suarez test show that the second-order Adams-Bashforth model has similar climate states to those of many other global models and it converges with resolutions. Based on the idealized baroclinic wave test, the capability of di?erent time di?erencing methods for keeping the initial steady-state are compared.This convinces a better ability of the second-order Adams-Bashforth method in maintaining the stability of the initial state. Furthermore, after the baroclinic wave is triggered through overlaying the steady-state initial conditions with the zonal perturbation, the second-order Adams-Bashforth method has an excellent property of convergence, and can represent the process of the baroclinic wave development much better than
the original scheme in CAM3.0. A long-term integration of the new model during the period of 1980-1999 is also carried out and compared with that of CAM3.0. It is found that due to the reduction of simulation errors of prognostic variables, the second-order Adams-Bashforth method also has a better simulation ability for the diagnostic variables, such as precipitation. 相似文献
13.
Comparison of different order Adams-Bashforth methods in an atmospheric general circulation model 下载免费PDF全文
下载免费PDF全文 The Asselin-Robert time filter used in the leapfrog scheme does degrade the accuracy of calculations. As an attractive alternative
to leapfrog time differencing, the second-order Adams-Bashforth method is not subject to time splitting instability and keeps
excellent calculation accuracy. A second-order Adams-Bashforth model has been developed, which represents better stability,
excellent convergence and improved simulation of prognostic variables. Based on these results, the higher-order Adams-Bashforth
methods are developed on the basis of NCAR (National Center for Atmospheric Research) CAM 3.1 (Community Atmosphere Model
3.1) and the characteristics of dynamical cores are analyzed in this paper. By using Lorenz nonlinear convective equations,
the filtered leapfrog scheme shows an excellent pattern for eliminating 2Δt wave solutions after 20 steps but represents less computational solution accuracy. The fourth-order Adams-Bashforth method
is closely converged to the exact solution and provides a reference against which other methods may be compared. Thus, the
Adams-Bashforth methods produce more accurate and convergent solution with differencing order increasing. The Held-Suarez
idealized test is carried out to demonstrate that all methods have similar climate states to the results of many other global
models for long-term integration. Besides, higher-order methods perform better in mass conservation and exhibit improvement
in simulating tropospheric westerly jets, which is likely equivalent to the advantages of increasing horizontal resolutions.
Based on the idealized baroclinic wave test, a better capability of the higher-order method in maintaining simulation stability
is convinced. Furthermore, after the baroclinic wave is triggered through overlaying the steady-state initial conditions with
the zonal perturbation, the higher-order method has a better ability in the simulation of baroclinic wave perturbation. 相似文献
14.
IAP AGCM4.0模式对热带大气季节内振荡的模拟评估 总被引：1，自引：1，他引：0
基于中国科学院大气物理所大气环流模式IAP AGCM4.0总共30年(1979~2008年)的模拟结果,评估了IAP AGCM4.0模式对热带大气季节内振荡的模拟能力。分析结果表明IAP AGCM4.0模式可以在一定程度上模拟出热带大气季节内振荡的主要时空谱结构特征,在周期30~80天处存在明显的谱能量中心;模式模拟的季节内振荡东传的主要特征与观测基本一致,东移波的能量远大于西移波。基于RMM指数(All-season Real-time Multivariate MJO Index)的分析表明,模式模拟的850 h Pa和200 h Pa季节内尺度风场和对流活动在赤道地区的空间分布与观测基本一致。但与观测相比,模式模拟的热带大气季节内振荡的周期较短,东传速度快于观测,虚假的西传特征过强,对流活跃区域范围较小、强度较弱。就非绝热加热而言,模式模拟结果与再分析资料比较接近,但最大加热在印度洋和西太平洋地区出现的位相较晚。进一步分析表明,模式中影响对流触发的相对湿度阈值(RHc)的不同取值(RHc分别取为85%、90%、95%和100%),可以显著影响热带大气非绝热加热垂直廓线,从而影响模式对热带大气季节内振荡的模拟;当对流触发相对湿度阈值取为90%时,IAP AGCM4.0模式对热带大气季节内振荡模拟的能力相对最好,非绝热加热垂直廓线在不同位相的分布特征也与再分析资料最为接近。这说明模式对流参数化方案中不同参数的合适选取,可以改进模式对热带大气季节内振荡的模拟能力。 相似文献
15.
大气环流模式中动力框架与物理过程的相互响应 总被引：7，自引：3，他引：4
用大气环流模式CAM3.1和IAP AGCM4.0对模式中动力框架与物理过程之间的相互作用及响应关系进行了初步探讨。选用理想的物理过程（Held-Suarez强迫）及完整物理参数化方案,分别对两个模式积分了60 d。试验表明,动力框架与物理过程之间的相互响应在低纬对流层和高纬对流层中上层有着较大的区别。在低纬对流层,动力框架及物理过程产生的温度倾向都有着较大的变率,对总的温度倾向的变率均有较大的贡献,且二者之间为相互补偿的反相关关系;在高纬对流层的中上层,总的温度倾向的变化主要依赖于动力框架的贡献,物理过程造成的倾向变化很缓慢,可近似地看做定常的强迫,且物理过程产生的温度倾向与动力框架产生的温度倾向之间为正位相的响应关系。此外,还对各个物理参数化方案之间的相互作用及响应关系进行了分析。结果表明,在所有过程中,湿过程所引起的温度倾向的变化最为显著,对总的物理过程倾向的贡献也最大;在高纬地区,长波辐射冷却也有较大的变率;短波辐射加热率及垂直扩散加热率的变化相对较小;长波辐射冷却和短波辐射加热之间为近似负反馈的响应关系。 相似文献
16.
北大西洋-东亚和北亚（简称NAENA）型遥相关是夏季欧亚大陆对流层上层经向风异常的第二主导模态,对欧亚大陆多尺度气候变率有显著影响。本文在分析NAENA型维持的动力学机制的基础上,研究了该遥相关型对新疆夏季旱涝异常的影响及其可能机制。大气波列的涡度收支分析表明,气候态的旋转纬向风引起的扰动涡度平流可以被扰动旋转经向风引起的平均涡度平流所补偿。能量转换过程分析表明,该大气波列有效地从平均流中提取有效位能,通过斜压能量转换过程得以维持。大西洋海温异常三极子模态则是NAENA型维持的重要外强迫因子。回归分析表明NAENA型遥相关能通过促进南疆夏季降水,显著影响新疆的旱涝异常。NAENA型位于中亚的气旋性低压一方面增强了南疆地区的垂直上升运动,同时气旋性环流将更多的水汽输送到该地区,有利于水汽在对流层中低层的异常辐合,进而对南疆的降水有促进作用。 相似文献
17.
In this paper, the dynamical effects of divergent wind on the intraseasonal variability of atmospheric circulation over East Asia are analyzed by using the function of Rossby-wave source and the energy exchanging function be-tween divergent component and rotational component of the flow.The results analyzed from the observed data show that the advection of vorticity by divergent wind caused by the heating due to the monsoon rainfall in the south to the Yangtze River and the strong convective activities around the Philippines may play an important role in the northward jump of westerly jet stream during the seasonal transition from spring circulation to summer circulation over East Asia. Due to the northward movement of the advection of vorticity by the divergent wind, the energy transformation from divergent component into rotational component can be caused over the Yellow River basin and Northwest China and will cause the intensification of the zonal flow there. Thus, the jet stream abruptly shifts northward to North China.Moreover, the analysed results also show that the advection of vorticity by divergent wind caused by the heating due to the strong convective activities around the Philippines also plays an important role in the intraseasonal varia-bility of the circulation over East Asia during the seasonal transition from summer to winter. With the southward movement of the advection of vorticity by the divergent wind, the energy transformation from divergent component into rotational component can be caused over East Asia, especially over the Yangtze-Huaihe River basin. Therefore, the jet stream gradually moves southward from North China to the Yangtze River basin. 相似文献
18.
IAP9L AGCM中大气季节内振荡的时空特征 总被引：4，自引：1，他引：3
根据IAP9LAGCM10年积分850hPa纬向风的逐日输出结果,应用Morlet小波分析方法,研究了该模式中的大气季节内振荡(MJO),结果表明该模式能抓住热带MJO的基本时空特征,模式中MJO的显著周期为36天;另外还分析了16～64天重构信号的时间经度剖面图,发现该MJO为东传,这与实际较一致;最后用EOF方法分析了模式大气中850hPa5天平均速度势,揭示出该MJO在全球表现为行星尺度1波和2波的特征。 相似文献