GLOBAL CHARACTERISTICS OF 30-60 DAY ATMOSPHERIC OSCILLATION
30—60天大气振荡的全球特征

The global characteristics of intraseasonal ( 30-60 day ) atmospheric oscillation are investigated by using ECMWF data . The distribution of kinetic energy of the 30 - 60 day oscillation shows it is a very large in the high latitudes. This means the 30-60 day atmospheric oscillation is prominent in the high latitudes as in the tropical atmosphere . The 30 - 60 day oscillations in the middle-high latitudes are clearly different properties with that in the tropical atmosphere . They are barotropical modes for vertical structure , dominated by perturbances of zonal wavenumbers 2 - 4 and propagate slowly westwards. The low - frequency teleconnection is very obvious for the 30 - 60 day oscillation . There are mainly the Europe-Asia-Pacific (EAP) pattern and PNA pattern in the Northern Hemisphere, and the Australia- South Africa ( ASA ) pattern and Round South America ( RSA ) pattern . Especially , above - low - frequency teleconnection patterns link each other in the global atmosphere and constitute two low - frequency wavetrains , i . e . EAP-ASA wavetrain and PNA-RSA wavetrain, or EAP-RSA wavetrain and ASA-PNA-wavetrain. There are obvious interactions of 30-60 day oscillation between the Northern and Southern Hemisphere, and their three fundamental processes are discussed in this paper.