A DIAGNOSTIC STUDY ON THE TEMPORAL AND SPATIAL CHARACTERISTICS OF THE TROPICAL INTRASEASONAL OSCILLATION

The climatic charact eristics of the tropical intraseasonal oscillation (TIO) were summarized by using the spectral analysis,wavelets analysis with some long term data sets.It is found that there are three regions where the TIO are veryactive.The first is the Western Pacific region where the tropical intraseasonal oscillation is most active.The second is the tropical Indian Ocean,the third is the region north to equator in the Eastern Pacific.The TIO has obvious seasonal transition.In western pacific and Indian oceans the TIO has two maximums during oneyear.In winter it is active in southern hemisphere (the Maximum is near 10°S),while in summer the maximum TIO center moves to northern hemisphere (near 10°N).However,it is weakened during spring and autumn.The TIO in eastern pacific north to the equator is active only in summer.It is very weak during winter and it does not shift to southern hemisphere atany time.For the large spatial scale meteorolog ical element,such as U wind field,the energy of the TIO mainly concent rates in the wave number 1.While for the relative small spatial scale elements such as precipitation,the energy of TIO is spread around wave 1 through wave 4.Though the TIO energy of wave 1 is the largest,the energy of wave 2-4 has similar order.The TIO is mainly eastward moving wave.And the TIO also has interannual and evenlonger variabilities,It is closely related to ENSO and the amplitude of the TIO had anabrupt increase in the end of 1970's.