共查询到20条相似文献，搜索用时 171 毫秒
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本文证明７种强迫作用激发经圈环流的线性叠加性，分项考察了各种物理强迫激发经圈环流的特征，通过考察一个数值模式的模式大气和实际大气各种物理强迫激发经圈环流的差异，分析了模式系统误差的成因，这种建立在动力背景之下的模式误差分析方法，其物理意义明确，具有较为普遍的适用性。 相似文献
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本文使用简化全球大气环流模式，研究大气环流型季节特征的成因问题。模拟了两类不同热机在大地形强迫背景下形成的环流型的异同之处，分析了两类热机对大气环流型季节特征的影响程度及其形成机理，从而得到关于大气环流型成因的较为直观、清晰的物理图象。 相似文献
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亚洲夏季风活动激发北半球大气遥相关的物理机制探讨 I.正规模及有限时间不稳定奇异矢量分析 总被引：3，自引：3，他引：0
造成大气环流异常的原因可以有两个方面, 一是大气内部的物理过程,另一方面则可能由大气外强迫引起。在线性框架内,该文的第I部分利用正规模（normal mode）以及有限时间不稳定奇异矢量（singular vectors）理论,对亚洲夏季风（ASM）活动激发北半球夏季遥相关型的大气内部物理机制进行了探讨。结果表明,亚洲季风区的扰动最有效地激发了它下游地区不稳定模态的发展,从而导致了从亚洲到北美洲一带的大气环流异常。关于从大气外强迫角度对这一问题的探讨,将在本文的第II部分发表。 相似文献
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雷兆崇 《南京气象学院学报》1981,(2)
本文利用1979年6月逐日的实测风资料,用间接推算法计算了90°E经圈剖面上的平均加热场,进而利用平均经圈环流诊断方程计算了不均匀的非绝热加热所驱动的平均经圈环流,并与转盘模拟实验、大气环流数值试验以及自然正交函数分解的结果进行了比较。本文指出1979年6用高原中部平均经圈环流以及逐日经圈环流作自然正交函数分解所得到的第二特征向量场,主要是由于不均匀的非绝热加热强迫形成的,从而显示了青藏高原热力作用对于初夏经圈环流的巨大影响。同时,本文还揭露了六月份北半球大气环流季节转换期间经围环流演变的特征。 相似文献
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造成大气环流异常的原因可以有两个方面, 一是大气内部的物理过程, 另一方面则可能由大气外强迫引起。在线性框架内, 该文的第 Ｉ 部分利用正规模 （ｎｏｒｍ ａｌ ｍｏｄｅ） 以及有限时间不稳定奇异矢量 （ｓｉｎｇｕｌａｒ ｖｅｃｔｏｒｓ） 理论, 对亚洲夏季风（ Ａ Ｓ Ｍ） 活动激发北半球夏季遥相关型的大气内部物理机制进行了探讨。结果表明, 亚洲季风区的扰动最有效地激发了它下游地区不稳定模态的发展, 从而导致了从亚洲到北美洲一带的大气环流异常。关于从大气外强迫角度对这一问题的探讨, 将在本文的第 Ｉ Ｉ部分发表。 相似文献
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利用最近发展的完备正规强迫模的动力学方法,对亚洲夏季风活动激发北半球大气遥相关的外部物理机制进行了探讨.结果表明,北半球夏季亚洲季风区是外强迫最敏感区域之一,最优强迫模与亚洲季风区季内时间尺度对流活动的结构特征相似,而且北半球大气对最优强迫模的响应与滞后于强季风候的环流异常型结构一致,由此可以认为,亚洲夏季风活动造成的热状况变化也是导致北半球大气遥相关的重要物理原因. 相似文献
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赤道移动性热源激发的大气强迫波和亚洲夏季风40—50天振荡 总被引：1，自引：0，他引：1
本文利用P－σ混合坐标系的五层原始方程模式研究了赤道移动性对流热源激发的大气强迫波和亚洲夏季风40－50振荡的关系。数值试验表明由Wave－CISK机制引起的移动性热源在沿赤道东移过程中可以引起亚洲夏季风环境、降水、赤道东－西纬向环流、季风经向环流和越赤道气流的位相振荡现象，其振荡周期与移动热源的移动速度有关。模拟结果进一步表明热带、付热带大气对赤道移动热源的响应可以激发出东传的Kelvinr波和东传的Rossby波，引起纬向差值气流和和戏向差值气流垢东传现象，以及扰动的北传现象。本文最后还讨论了东传的大气强迫波通过Walker环流和Hadley环流的影响而引起亚洲夏季风的40－40天振荡的机制。 相似文献
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It is proved in this paper that NWP systematic forecast errors in the zonal mean circulation aredue to the difference in westerly acceleration process during the forecasting period between model andreal atmospheres.Those forcing factors which evoke the zonal mean wind variation can be split into various linearterms according to the non-acceleration theorem in a primitive equation system,By applying this tech-nique to the diagnosis of the forecast produets of the T42L9 model in January 1992 and in July 1992,it is indicated that the model has the ability to forecast the zonal mean wind to a reasonable extent,but there are still some errors in several places,especially in the upper troposphere and lower strato-sphere in the mid-latitude region as well as near the surface.The results of analysis by employing thisscheme reveal the reason responsible for the systematic forecast errors of the zonal mean wind in themodel and the possible way of improving it.It is also shown that non-acceleration theorem can be used as an efficient tool to diagnose thephysical processes of NWP models. 相似文献
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证明了模式在预报时段的纬向平均环流误差，是由于在预报时段内模式大气和真实大气中西风加速过程的不同造成的。又由于原始方程的无加速定理中各强迫因子具有良好的线性迭加性，因此能够清楚地将造成模式系统误差的动力因子分解开来。通过对Ｔ４２Ｌ９模式的分析，说明原始方程的无加速定理可以作为分析模式系统误差的良好手段。动力诊断分析结果表明，模式对纬向平均环流分布具有较好的预报能力，但在各缔带也存在明显的误差。通过无加速定理的分解分析，本文研究了这些误差的成因及改善模式的可能途径。 相似文献
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Diana J. M. Greenslade Eric W. Schulz Jeff D. Kepert Graham R. Warren 《Journal of Atmospheric & Ocean Science》2005,10(3):261-287
Recent work has demonstrated that surface marine winds from the Bureau of Meteorology's operational Numerical Weather Prediction (NWP) systems are typically underestimated by 5 to 10%. This is likely to cause significant bias in modelled wave fields that are forced by these winds. A simple statistical adjustment of the wind components is shown to reduce the observed bias in Significant Wave Height considerably. The impact of increasing the vertical resolution of the NWP model and assimilating scatterometer data into the model is assessed by comparing the resulting forecast wind and waves to observations. It is found that, in general, the inclusion of scatterometer observations improves the accuracy of the surface wind forecasts. However, most of the improvement is shown to arise from the increased number of vertical levels in the atmospheric model, rather than directly from the use of the observations. When the wave model is forced with surface winds from the NWP model that includes scatterometer data, it is found that the scatterometer assimilation does not reduce the systematic bias in surface wave forecasts, but that the random errors are reduced. 相似文献
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Errors inevitably exist in numerical weather prediction (NWP) due to imperfect numeric and physical parameterizations. To eliminate these errors, by considering NWP as an inverse problem, an unknown term in the prediction equations can be estimated inversely by using the past data, which are presumed to represent the imperfection of the NWP model (model error, denoted as ME). In this first paper of a two-part series, an iteration method for obtaining the MEs in past intervals is presented, and the results from testing its convergence in idealized experiments are reported. Moreover, two batches of iteration tests were applied in the global forecast system of the Global and Regional Assimilation and Prediction System (GRAPES-GFS) for July-August 2009 and January-February 2010. The datasets associated with the initial conditions and sea surface temperature (SST) were both based on NCEP (National Centers for Environmental Prediction) FNL (final) data. The results showed that 6th h forecast errors were reduced to 10% of their original value after a 20-step iteration. Then, off-line forecast error corrections were estimated linearly based on the 2-month mean MEs and compared with forecast errors. The estimated error corrections agreed well with the forecast errors, but the linear growth rate of the estimation was steeper than the forecast error. The advantage of this iteration method is that the MEs can provide the foundation for online correction. A larger proportion of the forecast errors can be expected to be canceled out by properly introducing the model error correction into GRAPES-GFS. 相似文献
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伴随模式同化系统在修正模式误差中的应用研究 总被引：1，自引：1，他引：1
资料误差和模式误差都是制约数值预报结果准确性提高的关键因素,传统四维资料同化都是假设模式完全正确仅对初始资料进行修正,忽略了模式误差本身造成的预报误差。伴随模式同化系统不仅具有修正资料误差的能力,也可应用于修正模式误差方面的研究。本文将卫星中心导风系统提供的GMS5卫星风场与非常规温度资料用于MM5伴随同化系统修正模式地形误差进行试验性研究表明,该方法能够反演出一个既与初始气象要素场相匹配,又与模式更协调的地形场,得到比一般包络地形更好的效果,改善模式对强降水中心及降水区域的预报;数值试验结果还揭示模式误差对模式预报造成一定的影响,用伴随方法对观测资料进行修正的同时也对模式误差进行修正的方法是可行的。 相似文献
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The initial value error and the imperfect numerical model are usually considered as error sources of numerical weather prediction (NWP). By using past multi-time observations and model output, this study proposes a method to estimate imperfect numerical model error. This method can be inversely estimated through expressing the model error as a Lagrange interpolation polynomial, while the coefficients of polynomial are determined by past model performance. However, for practical application in the full NWP model, it is necessary to determine the following criteria: (1) the length of past data sufficient for estimation of the model errors, (2) a proper method of estimating the term "model integration with the exact solution" when solving the inverse problem, and (3) the extent to which this scheme is sensitive to the observational errors. In this study, such issues are resolved using a simple linear model, and an advection-diffusion model is applied to discuss the sensitivity of the method to an artificial error source. The results indicate that the forecast errors can be largely reduced using the proposed method if the proper length of past data is chosen. To address the three problems, it is determined that (1) a few data limited by the order of the corrector can be used, (2) trapezoidal approximation can be employed to estimate the "term" in this study; however, a more accurate method should be explored for an operational NWP model, and (3) the correction is sensitive to observational error. 相似文献
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数值天气预报中的两类反问题及一种数值解法──理想试验 总被引：14，自引：5，他引：14
针对数值预报中产生误差的两个来源提出了数值预报中存在着两类反问题。并在一维的非线性平流扩散方程上，用共轭方程的解法对提出的两类反问题作出了理想场的数值试验。试验结果表明，这种解反问题的方法非常有效。它利用＂观测资料＂所包含的时间演变的信息确定出了方程的初值或方程中误差订正项的空间分布状况。而且无论对＂观测资料＂的超定还是欠定都能得出较有意义的结果。因而有很大的利用前景。 相似文献
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相似集合是近年来提出的一种基于相似理论、大数据挖掘和集合预报思路的统计释用方法。文中首先介绍了相似集合的基本原理,并应用该方法对北京快速更新循环数值预报系统（BJ-RUC）v3.0预报地面要素开展了订正释用试验。结果表明,相似集合订正后,在0—36 h预报时段内,10 m风速的均方根误差降低44%,2 m气温的均方根误差降低22%,均方根误差均显著减小。对比测站预报误差的水平分布,相似集合方法的应用对于提升非城区站点的10 m风速预报、复杂地形区域的2 m气温预报具有更为明显的效果。相同预报因子的相似集合和支持向量机方法对模式10 m风速和2 m气温预报均具有显著且相似的订正效果,但相似集合方法具有计算资源需求较少、不需要大量人工干预的优势。相似集合方法形成的集合较好地模拟了模式平均误差的增长情况,集合离散度与集合平均均方根误差表现出理想的统计一致性,即相似集合方法在形成确定性预报的同时,还能够提供预报要素的不确定性或概率信息。因此,相似集合方法在模式预报订正及释用方面具有广阔的应用前景。 相似文献