Abstract: Under suitable imposed experimental parameters,near thermal Rossbv number ROT=0.1,and Taylor number Ta=2.2×107,the large-scale topography forcing produces low-frequency oscillation in the flow and rather long-lived flow pattern resembling blocking in the atmospheric circulation.The ‘blocking' phenomenon is caused by interaction and resonance of travelling waves and the quasi-stationary waves formed by topography forcing.The large-scale topography transforms wavenumber-homogeneous flows into mufti-wavenumber flows,and the topography-forced flows possess less wavenumber.