DIURNAL-VARIATION OF THE ISCCP CLOUDINESS

Seven January (1984 to 1990) months of three hourly monthly mean total cloud amount data were subjected to Empirical Orthogonal Function (EOF) analysis to study large scale features of the diurnal variation. The first two EOF modes explain two different types of diurnal variation. While the first EOF mode shows the diurnal variation contrast between land and ocean, the second EOF pattern shows diurnal variation over deep convective cloudy regions. In the second mode, maximum cloudiness occurs at around 2000 LST both over continental and oceanic regions, where deep convective cloudiness occurs. The first two EOF modes explain 78.4% of the total normalized variance. The time coefficients of these two EOF modes indicate that the diurnal variation of cloudiness undergoes non sinusoidal variation.