The disdrometer measures rain drop size distributions continuously and automatically. This instrument transforms the vertical momentum of an impacting raindrop into an electric pulse whose amplitude is a function of the drop diameter. A conventional pulse height analysis yields the size distribution of raindrops. The drop diameters that it can measure are in the range of 0.3 millimeter to 5 millimeter with an accuracy of ±5%.

To augment the instruments that provide microphysical information of rainfall at NARL and to derive relations that are being used in satellite and radar rainfall retrievals, NARL is operating a highly sophisticated 2D Video disdrometer (2DVD), supplied by Joanneum Research. Austria. The 2DVD provides not only accurate measurement of raindrop size distribution (DSD), but also information on the shape of each raindrop. It facilitates researchers to understand shape-size relations and DSD in a variety of rainfall systems and seasons, which is a vital input in many of the satellite and radar rainretrieval algorithms.