DITHER

     DITHER is used to specify the plotting behavior of the reflectivity
     intensities. A value of 0 specifies no dithering, the grid box is
     completely filled. Values 1-4 increase the number of dither points
     per grid box, approaching an increasingly opaque value. Dither
     can be used to overlay image data with radar reflectivity in
     order to simulate transparency. A dither value >= 5 will outline
     the grid box.