非绝热加热对中高纬大气低频振荡的调频作用

FREQUENCY MODULATION EFFECT OF DIABATIC HEATING ON ATMOSPHERIC LOW-FREQUENCY OSCILLATION IN THE EXTRATROPICAL LATITUDES

用诊断方法和数值试验两种方法，研究了非绝热加热对中高纬大气低频振荡的调频作用。首先应用１９７９～１９８９年欧洲中心资料进行功率谱分析，得到：（１）夏季与冬季相比，波动的主周期有缩短的趋势；（２）ＥｌＮｉｎｏ事件和ＬａＮｉｎａ事件期间，冬夏两季的波动主要周期分别有缩短和变长的趋势。然后，应用强迫耗散准地转正压涡度方程的全球谱模式，考虑三个行星波准共振，积分９０ｄ，得到：（１）三个行星波之间存在很强的波－波相互作用，且每个波都存在准双周和季节内振荡；（２）外源强度越强（弱），大气低频振荡周期将缩短（延长）；（３）外源强度和位置不同，非绝热加热对中高纬大气低频振荡的调频作用也不同。上述结果与作者以前的理论分析结果相当一致。

By both the diagnostic and numerical experiment method, the frequency modulation effect of diabatic heating on atmospheric low-frequency oscillation (LFO) in the mid-high latitudes is researched . First the power spectral analysis is performed for the 1979￣1989 ECMWF data.The results show:(1) The main periods of waves have the shortened tendency in summer comparing to those in winter.(2) The main periods of waves in the both seasons tend to shorten and lengthen during El Nino and La Nina events, respectively. By a forcing and dissipative global spectral model of quasi-geostrophic barotropic vorticity equation the numerical experiments are run for 90 days on the condition of 3-wave quasi-resonance. The results are given as follows:(1)there exist strong interactions among the three planetary waves, and there also exist quasi-two-week and intraseasonal oscillations in every wave; (2)The stronger (weaker) the external source ,the periods of LFO the shorter (longer); (3)The frequency modulation effects of diabatic heating on LFO in the mid-high latitudes are different due to the difference in the strength and location of external sources. The above results are consistent with the former theoretical results obtained by Lu.