Forcing Mechanism of Normal Mode Rossby Waves

常模Rossby波是大气中向西传播的自由波，其特征周期为5-20天。本文分析了卫星观测资料和利用大气环流模式(GCMS)进行数值模拟的结果：(1)利用美国国家航空航天局(NASA)的UARS/ISAMS资料首次在中层显示了全球5天和10天波的结构，(2)5天波和10天波在中层上层都是逐渐变高的；基于GCM模拟的结果表明：(1)模拟的5日波与实测波的垂直和水平结构非常相似，出现的周期约为1个月.(2)对5日波和降水的详细分析表明，当纬向波数1的降水场异常较大，且周期为5天时，5天波的活动倾向于显著增强.(3)5天波在无山和/或无海陆对比的情况下也出现，因此对激发浪可能不重要.然而，在潜热释放去除的情况下，5日波活动明显较弱。

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.