Structural and Textural Characteristics of Cirrus Clouds Observed Using High Spatial Resolution LANDSAT Imagery

Abstract

Twelve cirrus scenes are analyzed to determine textural and structural features using LANDSAT imagery. The main structural characteristics are: 1) cirrus cloud size distributions obey a power law, with larger cloud cells (D ⩾ 1.5 km) having smaller slopes than smaller cloud elements; 2) convective-type cirrus are fractal in nature with fractal dimensions of ≈ 1.4, while stratiform cirrus clouds show bifractal behavior, with larger clouds having smaller fractal dimensions (≈1.3); 3) stratiform cirrus cloud cells have significantly larger horizontal aspect ratio than do smaller cells; and 4) structural results are not sensitive to threshold selection. The main textural characteristics are: 1) convective cirrus clouds have high contrast measures and a rapid decrease of correlation at short distances, while stratiform cirrus clouds have low contrast measures and more gradual slopes; 2) asymptotic values are good descriptors of general characteristics (macrotexture) of cloud fields, while the slopes of textural measure curves at small distances reveal information about cloud field microtexture; 3) contrast and correlation appear to be the best discriminators of cloud field structure, and their directional measures show preferred cloud field orientation; and 4) correlation measures are sensitive to threshold selection for cirrostratus cases.