Maps, plots, or graphical presentations of weather radar observations designed to facilitate interpretation of the observations. Some displays are maps of such basic quantities as reflectivity factor or mean Doppler velocity on polar or other coordinate systems (See PPI and RHI). Others are maps of derived quantities, such as rainfall rate or vertically integrated liquid water; or of quantities or phenomena based on computer algorithms, such as vortex signatures, downbursts, fronts, or regions where hail is likely. Another class of radar display is employed for special analyses, for example, the VAD used for kinematic analysis of the wind field.