Interannual Cloudiness Changes

Abstract

Based on monthly mean satellite cloudiness data over the tropical belt between 25°S and 25°N from February 1965 to July 1973, covering 102 months, the intensity of interannual changes in perturbation cloudiness, as measured from the standard deviation, was found to be a maximum over the equatorial western Pacific. The equatorial region between 15°S and 15°N is characterized by large interannual changes in cloudiness perturbations with wavenumbers 1 and 2, which occur without apparent connection with the changes in zonal mean cloudiness. Of particular interest is the tendency for the zonal mean cloudiness to increase or decrease almost simultaneously at all latitudes between 25°5 and 25°N. Cloudiness anomalies over the western North Pacific are negatively correlated with the anomaly cloudiness over the eastern North Pacific. Similar inverse relationship is found between cloudiness anomalies over the western and eastern South Pacific. It appears that interannual cloudiness changes are coherent over a considerable geographical extent and strongly indicate a form of atmospheric teleconnection between the western North Pacific and other parts of the Pacific region. Through computations of time lag correlation, it was found that above (below) normal cloudiness in the western North Pacific near 140°E, 20°N takes place about 5 months prior to the anomaly cloudiness maximum (minimum) over the western South Pacific near Australia.