共查询到19条相似文献，搜索用时 203 毫秒
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34层线性球面原始方程谱模式与模式大气对地形强迫的响应 总被引：1，自引：2，他引：1
本文建立了一个34层包括牛顿冷却、Rayleigh摩擦和非绝热加热线性原始方程谱模式。用此模式对地形强迫为下边界条件进行时间积分。结果表明,此模式计算稳定,有较好的精度及计算时间节省的特点模式的积分结果还表明,此模式对球面大气准定常行星波的形成和传播有较好的描写能力。 相似文献
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本文用二层准地转截断谱模式,解析地指出,在一定的条件下,地形强迫作用能够激发出地形驻波或地形瞬变波.给出了地形驻波的表达式并初步讨论了地面摩擦、垂直向及水平向内摩擦在地形驻波形成中的作用.地形瞬变波振荡频率的解析表达式及有关计算表明,两周左右的中期波振荡,就其动力学性质而言,有些是自由的斜压波,有些是受地形强迫影响的地形瞬变波.Charney曾解析地讨论了正压大气中一种地形驻波的稳定性,本文将此扩展到斜压的情况,所得的结果基本上是一致的. 相似文献
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本文用二层准地转截断谱模式,研究了大气环流形态的分支现象.结果指出:依赖于热力强迫的不同取值,模式大气将显示出等温静止或Hadley环流两类定常流型,Hadley流型并具有基本解的属性.在热力强迫达到Hadley流型的分支点以前,Hadley流型是稳定的;到达分支点后,Hadley流型不稳定,激发出新的流型,显现出分支现象.绝热无地形时,分支出瞬变斜压波;绝热有地形时,在不同的分支点分别激发出地形驻波与地形瞬变波;非绝热时,分支出非绝热驻波或非绝热驻波与瞬变斜压波的混合波型,非绝热驻波失稳激发出二级分支, 相似文献
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本文根据两层斜压模式得到大尺度地形对1000—500mb 平均温度场的常定扰动.结果得到大地形对温度槽脊的形成具有一定的作用,而地形所造成的高度槽在垂直方向上没有倾斜现象. 相似文献
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本文利用北半球正压原始方程模式和理想初始场，加入北半球实际的平滑地形的作用，对北半球超长波2波型、3波型、长波4波型、5波型，分别进行了240小时的积分计算。从考虑地形和不考虑地形的四组结果对比中，发现地形对上述四种波型的演变有很大的影响，证实了地形作用确系影响大气环流、形成某些天气气候特征的重要因素之一；同时发现，在地形的动力作用下，北半球大气形成了一些重要的环流系统。例如，极涡向北欧偏移，东亚、北美大槽和阿拉斯加脊的维持，都与地形有密切关系。在地形作用下:（1）北太平洋西槽东脊，而北大西洋西脊东槽。（2）阻塞和切断形势的出现更为频繁、典型。（3）在欧亚大陆上，m=4时出现倒Ω流型，而m=5时，出现两槽一脊型。 相似文献
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分块地形坐标大气环流模式框架的计算稳定性及数值试验 总被引：2，自引：1，他引：1
用数值试验方法讨论了分块地形η坐标大气环流模式动力框架的计算稳定性; 采用实际初始场, 该框架能够长期稳定地积分.在积分前100d内总有效能量变化很小, 总质量守恒、各物理量场的数值和波形都得到很好保持, 这表明该框架稳定性好.在分析了该框架的积分结果后可知其合乎物理事实, 与IAP 2.0的动力框架相比, 能更好地反映出大地形的环流形势, 这说明有大地形时采用分块地形η坐标要较σ坐标好.另外, 还对青藏高原等大地形的纯机械强迫作了数值试验, 得到了地形强迫平均槽脊的分布特征, 给出了地形纯机械强迫造成的准定常行星波的图像. 这些工作表明采用分块地形η坐标处理大地形是合理可行的. 相似文献
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斜压西风带中大地形有限扰动的动力学 总被引：6，自引：2，他引：6
本文指出,对于无黏性的、绝热的斜压大气的大尺度常定有限扰动,可以用一个三维的Helmholtz 方程来描写.在地形存在的边界条件下,获得了该方程的解答.用西藏高原(包括亚洲山系)和洛矶山的实际地形作了数值计算,计算结果表明,地形扰动可以解释西风带平均槽脊的位置,但扰动的强度与实况有一些出入.计算结果亦表明,大地形对西风带的扰动随高度很快阻尼,因此看来大地形对西风带的扰动在对流层低层更为重要. 相似文献
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爆发性气旋发展中斜压强迫与潜热释放作用的数值试验 总被引：2，自引：0，他引：2
本文利用一个六层原始方程模式对五例爆发性气旋的发展进行了数值试验,试验结果表明：斜压强迫是气旋爆发性发展的基本因子,而潜热释放的重要性则有较大差异。潜热释放的作用主要集中在两个方面：一是对低层的直接增暖,加强了上升运动;二是对局地斜压性的加强,促进了锋面、槽脊系统的发展,而这两者均有利于气旋的发展。 相似文献
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雷兆崇 《南京气象学院学报》1988,(4)
本文利用一个包含了Newton冷却Rayleigh摩擦以及▽~4水平扩散等耗散作用的定常、斜压、线性初始方程三维谱模式,研究了中、高纬度理想化的大尺度地形以及北半球实际地形的动力强迫作用对于行星尺度的大气定常波的影响。计算结果证实了简化的β平面正压理论的定性结论。地形动力强迫作用所导致的大气定常波具有相当正压的垂直结构,其对应的扰动流场在中、高纬地区旋转(无辐散)分量占据主导地位,而辐散(无旋)分量则主要集中在低纬区域。北半球实际地形所强迫的大尺度扰动,主要表现为纬向波数为2的行星波,其中青藏高原的贡献具有头等重要的意义,相对而言,落基山和恪陵兰高原的贡献则是第二位的。 相似文献
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线性和非线性地形罗斯贝波 总被引：1，自引：0，他引：1
本文在半地转概念下,讨论了线性和非线性地形罗斯贝波的稳定性及其解。指出:线性和非线性稳定性判据形式一致。在线性时,地形东西向及南北向坡度对稳定波动的周期和传播速度有明显影响,其解为周期函数;在不稳定时,解为非周期函数。二级近似时其解为孤立波形式——不稳定时,在地形不同位置可形成东移或西移的孤立波槽或孤立波脊;而在稳定时只形成孤立波槽。三级近似时解出现间断点。 相似文献
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This study examines wave disturbances on submonthly (6–30-day) timescales over the tropical Indian Ocean during Southern Hemisphere summer using Japanese Reanalysis (JRA25-JCDAS) products and National Oceanic and Atmospheric Administration outgoing longwave radiation data. The analysis period is December–February for the 29 years from 1979/1980 through 2007/2008. An extended empirical orthogonal function (EEOF) analysis of daily 850-hPa meridional wind anomalies reveals a well-organized wave-train pattern as a dominant mode of variability over the tropical Indian Ocean. Daily lagged composite analyses for various atmospheric variables based on the EEOF result show the structure and evolution of a wave train consisting of meridionally elongated troughs and ridges along the Indian Ocean Intertropical Convergence Zone (ITCZ). The wave train is oriented in a northeast–southwest direction from Sumatra toward Madagascar. The waves have zonal wavelengths of about 3,000–5,000 km and exhibit westward and southwestward phase propagation. Individual troughs and ridges as part of the wave train sequentially travel westward and southwestward from the west of Sumatra into Madagascar. Meanwhile, eastward and northeastward amplification of the wave train occurs associated with the successive growth of new troughs and ridges over the equatorial eastern Indian Ocean. This could be induced by eastward and northeastward wave energy dispersion from the southwestern to eastern Indian Ocean along the mean monsoon westerly flow. In addition, the waves modulate the ITCZ convection. Correlation statistics show the average behavior of the wave disturbances over the tropical Indian Ocean. These statistics and other diagnostic measures are used to characterize the waves obtained from the composite analysis. The waves appear to be connected to the monsoon westerly flow. The waves tend to propagate through a band of the large meridional gradient of absolute vorticity produced by the mean monsoon westerly flow. This suggests that the monsoon westerly flow provides favorable background conditions for the propagation and maintenance of the waves and acts as a waveguide over the tropical Indian Ocean. The horizontal structure of the wave train may be interpreted as that of a mixture of equatorial Rossby waves and mixed Rossby-gravity wavelike gyres. 相似文献
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EASTWARD MOVEMENT OF MIDLATITUDE LOW FREQUENCY WAVES AND THEIR INTERACTION WITH SYSTEM DOWNSTREAM* 
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下载免费PDF全文 Luo Zhexian 《Acta Meteorologica Sinica》1990,4(5):569-575
Within the framework of forcing/dissipation KDV dynamics, the effect is numerically studied of successive east-travelling troughs on quasi-stationary high's ridges downstream. Results show that two types of low-frequency transiency are available, depending on the intensities of down-drifting troughs. One is that transiency occurs in strength, i.e., the ridge undergoes transient change in intensity with unchanged position; the other is that transiency takes place in pattern, viz., the breakdown of the quasistationary character of the ridge's posi-tion, meaning that the ridge is replaced by a trough, followed by multiple transformation between ridge and trough. 相似文献
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Wang Zonghao Mao Jianping Huang Jihong Arnold Gruber Albert Thomasell Tan Sun Chen 《Acta Meteorologica Sinica》1992,6(4):421-432
This paper is to examine the impact of satellite data on the systematic error of operational B-model in China.Em-phasis is put on the study of the impact of satellite sounding data on forecasts of the sea level pressure field and 500 hPaheight.The major findings are as follows.(1)The B-model usually underforecasts the strength of features in the sea level pressure(SLP)field,i.e.pressuresare too low near high pressure systems and too high near low pressure systems.(2)The nature of the systematic errors found in the 500 hPa height forecasts is not as clear cut as that of the SLPforecasts,but most often the same type of pattern is seen,i.e.,the heights in troughs are not low enough and those inridges are not high enough.(3)The use of satellite data in the B-model analysis/forecast system is found to have an impact upon the model'sforecast of SLP and 500 hPa height.Systematic errors in the vicinity of surface lows/500 hPa troughs over the oceansare usually found to be significantly reduced.A less conclusive mix of positive and negative impacts was found for allother types of features. 相似文献