CHAPTER 2 WEATHER RADAR

Aerographers Mate, Module 03-Environmental Satellites and Weather Radar
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CHAPTER 2 WEATHER RADAR INTRODUCTION Since the late 1940’s, radar has been used to track weather systems. Subsequent advances were made in radar transmitters, receivers, and other system components. However, with the exception of transistor technology, few changes were made to basic weather radar systems through the 1970’s. In the late 1970's, work began on the "next-generation” of weather radar (NEXRAD) using Doppler technology. The use of Doppler technology enabled weather radar systems to not only detect meteorological targets with greater detail, but also measure target motion and velocity. By the mid 1980’s, a new weather radar that used this technology was introduced. This system is known as the weather surveillance radar-1988-Doppler, or WSR-88D. WSR-88D systems have been installed at several Navy and Marine Corps shore-based weather stations. Even if you do not have a WSR-88D at your command, almost all weather radar information you will receive is derived from Doppler radar. Thus, it is important that you understand basic Doppler theory and the WSR-88D system. In this chapter we discuss the Doppler weather radar (WSR-88D). We begin with a general explana- tion of electromagnetic energy and radar propagation theory followed by a discussion of Doppler radar principles. We will then concentrate on the configuration and operation of the WSR-88D system. Finally, we complete the chapter with a discussion of the advantages and limitations of WSR-88D products, and the publications associated with the system. ELECTROMAGNETIC ENERGY LEARNING OBJECTIVES: Describe the properties of electromagnetic energy. Define electromagnetic wave, electromagnetic spectrum, wavelength, amplitude, frequency, and Rower. Understanding the fundamentals of electromagnetic (EM) energy will enhance your ability to use weather radar. No matter how sophisticated the radar system, theoretical limitations always exist. This background knowledge will also help you to understand the operation of the WSR-88D and to effectively use the products it produces. In the following text, we will begin with a general discussion of electromagnetic energy followed by a description of several properties related to electromagnetic waves. ELECTROMAGNETIC WAVES As discussed in chapter 1 of this module, all things (whose temperature is above absolute zero) emit radiation. Radiation is energy that travels in the form of waves. If this energy were visible, it would appear as sine waves, with a series of troughs and crests (fig. 2-1). Because radiation waves have electrical and Figure 2-1.—Electromagnetic energy as sine waves. 2-1

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