科研之友
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摘要
the meteorological phenomena that occur in the central amazonia (manaus) are studied from isccp-c1 satellite- based data. the oscillations that contribute more significantly to the cloud cover variability and its relation to el niˋo and la niˋa events case identified. the annual and semi-annual oscillation times scales are the main responsible for the variability of the high cloud cover over manaus. the inter-annual oscillations associated with el niˋo and la niˋa events also contribute significantly to the total variability of the high cloud cover, while intraseasonal and day-to-day oscillations show a reduced contribution. however, the intraseasonal and day-to-day oscillations are important since they do influence the predictability on short and medium range forecast. the studied region was extended to 21 sections, centered in manaus. the 60, 45 and 30 day-oscillations exhibited a higher spectral power density percentage over eastern manaus; the 20 day-oscillations, over the central manaus; and the 8, 6 and 4 day-oscillations, over western manaus. the cold fronts that reach central amazonia modulate convective activity over manaus region, acting as a forcing for day-to-day oscillations (47% of the cases), intraseasonal oscillations (15%), and 55 to 65 day- oscillations (13%). it is important to point out that the cold fronts did not necessarily establish the oscillations, but they may have favored or induced convection over manaus region.
