The　Dynamical　Influence　of　Land－Sea　Contrast　and　Sea　Surface　Temperature　on　Intraseasonal　Oscillation　in　Tropical　Atmosphere  

作　　者：杨燕 朱抱真 

出　　处：《Advances in Atmospheric Sciences》1995年第4期405-418,共14页大气科学进展（英文版）

摘　　要：An equatorial β-plane model which includes realistic non-uniform land-sea contrast and the underlying surface temperature distribution is used to simulate the 30-60 day oscillation (LFO) processes in tropical atmosphere, with emphasis on its longitude-dependent evolution and convective seesaw between Indian and the western Pacific oceans.The model simulated the twice-amplification of the disturbances over indian and the western Pacific oceans while they are travelling eastward.It reproduced the dipole structure caused by the out-of-phase oscillation of the active centres in these two areas and the periodical transition between the phases of LFO.It is suggested that the convective seesaw is the result of interaction of the internal dynamics of tropical atmosphere with the zonally non-uniform thermal forcing from underlying surface.The convective activities are suppressed over indonesia maritime continents whilst they are favoured over the Indian Ocean and western Pacific warm waters, so there formed two active oscillation centres. The feedback of convection with large-scale flow slows down the propagation of disturbances when they are intensifying over these two areas, therefore they manifest a kind of quasi-stationary component to favor the 'dipole' structure. Whereas the disturbances weaken and speed up over the eastern Pacific cold water region due to the interaction of sensible heating and evaporation with perturbational wind. Therefore the two major centers just show out-of-phase oscillation during one cycle around the latitudinal belt.By introducing the SST anomalies in El Nino and La Nina years into the surface temperature,we also show that they have significant influence on LFO processes. In an anomalously warm year, the LFO disturbances dissipate more slowly over the central-eastern Pacific region and can travel further eastward; whilst in an anomalously cold year,the opposite is true.An equatorial β-plane model which includes realistic non-uniform land-sea contrast and the underlying surface temperature distribution is used to simulate the 30-60 day oscillation (LFO) processes in tropical atmosphere, with emphasis on its longitude-dependent evolution and convective seesaw between Indian and the western Pacific oceans.The model simulated the twice-amplification of the disturbances over indian and the western Pacific oceans while they are travelling eastward.It reproduced the dipole structure caused by the out-of-phase oscillation of the active centres in these two areas and the periodical transition between the phases of LFO.It is suggested that the convective seesaw is the result of interaction of the internal dynamics of tropical atmosphere with the zonally non-uniform thermal forcing from underlying surface.The convective activities are suppressed over indonesia maritime continents whilst they are favoured over the Indian Ocean and western Pacific warm waters, so there formed two active oscillation centres. The feedback of convection with large-scale flow slows down the propagation of disturbances when they are intensifying over these two areas, therefore they manifest a kind of quasi-stationary component to favor the 'dipole' structure. Whereas the disturbances weaken and speed up over the eastern Pacific cold water region due to the interaction of sensible heating and evaporation with perturbational wind. Therefore the two major centers just show out-of-phase oscillation during one cycle around the latitudinal belt.By introducing the SST anomalies in El Nino and La Nina years into the surface temperature,we also show that they have significant influence on LFO processes. In an anomalously warm year, the LFO disturbances dissipate more slowly over the central-eastern Pacific region and can travel further eastward; whilst in an anomalously cold year,the opposite is true.

关 键 词：Low frequency oscillation Convective seesaw Tropical model 

分 类 号：P43[天文地球—大气科学及气象学]