Forcing Mechanism of Normal Mode Rossby Waves

正态罗斯比波是大气向西传播的自由波，特征周期为5-20天。本研究包括对卫星观测资料的分析和利用大气环流模式（GCMs）的数值模拟基于观测资料分析的结果：(1)利用NASA获得的UARS/ISAMS数据，首次在中间层显示了5日波和10日波的全球结构。(2) 5日波和10日波在中层上层均随高度逐渐增大；尽管如此，冬季半球的10天波振幅很大基于GCM模拟的结果表明：(1)模拟的5天波的垂直和水平结构与观测的非常相似，出现不规则，寿命约为1个月。(2)对5日波和降水的详细分析表明，当纬向1波数降水场异常较大且向西周期为5 d时，5日波活动倾向于大幅度增强。(3)无山、无海陆对比条件下也会出现5日波；因此这些对于波的激发可能是不重要的。然而，在潜热释放消失的情况下，5天波活动明显减弱。

Normal mode Rossby waves are westward traveling free waves of the atmosphere with characteristic periods of 5-20 days. The present study consists of analyzes of observed data obtained by satellite measurements and numerical simulation by the use of general circulation models (GCMs).1 Results based on analyzes of observed data :(1) Global structures of 5-day and 10-day waves are firstly shown in the mesosphere by the use of UARS/ISAMS data obtained through NASA.(2) Both the 5-day and 10-day waves are gradually with height in the upper mesosphere ; nonetheless 10-day waves have large amplitudes in the winter hemisphere.2 Results based on GCM simulation :(1) Simulated 5-day waves have vertical and horizontal structure very similar to that of observed ones and appear irregularly with a lifetime of about one month.(2) Detailed analyzes for 5-day waves and precipitations show the evidence that 5-days wave activities are inclined to be largely enhanced when anomalies in the precipitation field of zonal wavenumber 1 are large with a westward period of 5 days.(3) 5-day waves also appear in conditions of no mountains and/or no land-sea contrast ; hence these are probably unimportant for excitation of the waves. However, 5-day wave activities are significantly weak in case of removal of the latent heat release.