-
Step 1
Know that Doppler works by emitting radio waves from an antenna and measuring how different atmospheric conditions affect them. Raindrops, hail and other objects in the air reflect the waves back. When objects move toward the antenna, the frequency of the waves increases, whereas when objects move away, the frequency decreases.
-
Step 2
Understand that Doppler radar differs from standard radar in that Doppler tracks wind activity both inside of storms and when no precipitation exists. With this ability, Doppler can better predict dangerous weather like hurricanes.
-
Step 3
Recognize that the colors on a "reflectivity" Doppler image represent the level of precipitation. Look at the computerized Doppler image for a legend of the colors: the higher the value, the stronger the rate of precipitation. "Reflectivity" is the intensity of the wave frequency echoed back to the antenna. It is available from different angles of the antenna and predicts precipitation. "Base" reflectivity is the measurement from one angle of the antenna, whereas composite reflectivity is the sum of all angles.
-
Step 4
Identify the colors on a "base velocity" or "storm relative motion" Doppler image. This image represents an overall gauge of wind activity within range of the antenna. Green colors show wind moving toward the radar and red colors show wind moving away. Grayish colors indicate the transition zone between incoming and outgoing winds. Read the image more easily by pinpointing the location of the antenna (usually somewhere along the point where the red and green areas meet).
-
Step 5
Beware of occasional inaccuracies in Doppler radar reporting of precipitation levels. The radar will overestimate the level of precipitation during hailstorms because hail reflects stronger echoes. However, radar may also under or overestimate precipitation levels if it is improperly calibrated.
-
Step 6
Do not look for the sweeping line seen on older Doppler images. The line represented an old analog type of radar, and as the new image was transmitted, the line would sweep across the screen to overwrite the old data with the new. Today, digital radar waits until obtaining the full 360 degrees of information before updating the image, and, therefore, does not use the line.
