Abstract
This study deals with the identification of precipitation and ground echoes in radar images using their textural features. The images were collected by meteorological radars in the regions of Setif (Algeria) and Bordeaux (France). Two kinds of texture-based techniques have been considered, consisting in calculating either the histograms of grey levels or the histograms of their sum and difference. Hence, the first-order probability distributions were found to be sufficient to account for the textural features of radar images. Energy is found to be the textural parameter that clearly distinguishes between precipitation and ground echoes. With both methods, fixed ground echoes and anaprops are efficiently rejected, whereas precipitation echoes are kept almost unchanged. These methods have the advantages of effectiveness and simplicity. The threshold of discrimination is independent of the geographical and climatic conditions in the regions under study. Because the computation time needed by these techniques is small, the radar images can be processed in real-time.
Highlights
Meteorological radars are today acknowledged as efficient tools for detecting precipitation fields in a given region
The pixels sorted by histogram approach as precipitation and ground echoes are assigned to the third data sample and those classified by sum and difference histogram approach form the fourth data sample
For the sake of clarity in the computation, the number of pixels of echoes identified by histogram and sum and difference histogram approaches are, respectively, denoted Xa and Ya
Summary
Meteorological radars are today acknowledged as efficient tools for detecting precipitation fields in a given region These radars collect images made of echoes mostly caused by rainfall. When super-refraction settles down and when the air refractive index strongly varies with altitude, electromagnetic waves arising from the radar propagate through atmospheric ducts and are backscattered by the ground obstacles. In such conditions, another type of disturbing ground echoes, called anaprops or AP echoes (anomalous propagation), sometimes appears at various distances from the radar. Anaprops depend on the state of the lower atmosphere They are sporadic, vary slowly in position and cause many false observations of precipitation.
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