T This radar system determines the velocity of a cell heading toward, or away from a frequency transmission site. Doppler radars are used in meteorology to forecast hazardous weather by transmitting electromagnetic radiation waves at specific frequencies towards an object. When a Doppler radar’s signal is sent out towards an object at a determined frequency, the signal is returned back to the source with certain data to calculate the objects velocity (difference in frequencies between the transmitted and received frequency). When the return frequency is higher than the transmitted, the cell is moving closer to the site.

However, the cell is moving further from the site when the received frequency is lower than what was transmitted. One type of Doppler radar is the pulse-Doppler radar system, which allows meteorologists to calculate radial and linear velocities. One unique factor about the pulse-Doppler system is that it sends out pulses of electromagnetic frequencies instead of beams. The name “Doppler” came from the Austrian physicist Christian Andreas Doppler, who discovered that frequencies of sound and light waves bouncing from a source to a moving object and back, can detect its velocity (Doppler Effect).

Works Cited 1. Lim, Eunha and Sun, Juanzhen “A Velocity Dealiasing Technique Using Rapidly Updated Analysis from a Four-Dimensional Variational Doppler Radar Data Assimilation System” Journal of Atmospheric and Oceanic Technology Volume. 27 p. 12 Print. 2. http://inventors. about. com/library/inventors/blradar. htm 3. http://physics. about. com/od/physicsintherealworld/f/dopplerradar. htm 4. Lester. Peter “Aviation Weather” Jeppesen 2007