Wavelength

Figure 2-3.—Horizontally and vertically polarized electromagnetic waves. Wavelength The distance from wave crest to wave crest (or trough to trough) along an electromagnetic wave’s direction of travel is called wavelength. Each measurement equals one complete wave, or wave cycle, and is typically expressed in centimeters. Each wavelength can also be described in terms of degrees, with one wavelength equal to 360° (fig. 2-4). This concept will become very important later, when we discuss Doppler radar. As radar energy is emitted into the atmosphere, it encounters particles of dust, dirt, and salts, in addition to water vapor and precipitation. Collectively, these are known as scatterers, and they have an important effect on radar effectiveness. Wavelength plays a critical role in a weather radar’s ability to see scatterers, that is, water droplets. Shorter wavelengths provide more detail and allow detection of small droplets, while longer wavelengths are best for larger targets, such as precipitation from rain showers and thunderstorms. It is important that a radar wavelength Figure 2-4.—Wavelength of an electromagnetic wave. 2-3