摘要:
大气长波的发展和演变影响着大气的可预报性,并对提高天气预报和气候预测水平有重要的意义.在影响大气长波演变的因子中,除波与波非线性相互作用外,基流的作用也非常重要.本文利用非均匀基本场下Rossby波运动方程,通过数值求解,分析了基本场结构和初始场对Rossby波演变的影响,揭示了纬向非均匀基本场对长波调整的作用.研究结果表明:基流纬向非均匀时,线性Rossby波也会出现长波调整现象,基流随纬向变化是长波发生调整的又一个重要机制;大气长波调整对波动的初始振幅不敏感,但基本场振幅影响着长波调整能否出现和出现的时间;基本场纬向平均西风基流的大小除影响波动传播的速度和方向外,还影响长波调整出现的时间和规律;长波调整的出现还与基本场和初始场的结构有关,不同基本场时,波动是否发生调整、向高波数还是向低波数调整都决定于基本场结构,相同基本场时,不同初始结构的波动也有着不同的演变过程.
关键词:
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基流
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非均匀
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大气长波
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调整
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演变
Abstract:
The development and evolution of atmospheric long-wave has an important impact on the atmospheric predictability, and is important to improve weather and climate prediction. In addition to the wave-wave nonlinear interaction, the basic flow is also a significant factor of the atmospheric long-wave adjustment. Based on equations of Rossby wave within non-uniform basic flow, the numerical solution is calculated to study the effect of basic flow's structure and initial condition on the evolution of Rossby wave. The result indicates that, in linear context, the Rossby wave also presents adjustment of long-wave in the presence of zonal non-uniform basic flow. Therefore, the zonal non-uniform basic flow is another important mechanism for adjustment of long-wave. The adjustment is not sensitive to the amplitude of initial fluctuations. However, it is found that the amplitude of the basic flow determines the emergence and start time of long-wave adjustment. The zonal average of basic flow can also affect the long-wave. It not only has impacts on the speed and direction of Rossby wave propagation, but also affects the time of adjustment occurrence and its evolution characteristic. The adjustment is also correlated with the structure of the basic field and the initial field. The structure of basic flow decides the emergence and direction of adjustment. On the premise of same basic flow, the initial fluctuations with different structures also have different evolutions of wave.
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