Hail is a form of solid precipitation. It is distinct from ice pellets, though the two are often confused. It consists of balls or irregular lumps of ice, each of which is called a hailstone. Ice pellets generally fall in cold weather, while hail growth is greatly inhibited during cold surface temperatures.
Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ranges as microwaves; the above broad definition includes both UHF and EHF bands. A more common definition in radio-frequency engineering is the range between 1 and 100 GHz. In all cases, microwaves include the entire SHF band at minimum. Frequencies in the microwave range are often referred to by their IEEE radar band designations: S, C, X, Ku, K, or Ka band, or by similar NATO or EU designations.
Radar is a detection system that uses radio waves to determine the distance (ranging), angle, or velocity of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. A radar system consists of a transmitter producing electromagnetic waves in the radio or microwaves domain, a transmitting antenna, a receiving antenna and a receiver and processor to determine properties of the object(s). Radio waves from the transmitter reflect off the object and return to the receiver, giving information about the object's location and speed.
In antenna theory, a phased array usually means an electronically scanned array, a computer-controlled array of antennas which creates a beam of radio waves that can be electronically steered to point in different directions without moving the antennas.
A Doppler radar is a specialized radar that uses the Doppler effect to produce velocity data about objects at a distance. It does this by bouncing a microwave signal off a desired target and analyzing how the object's motion has altered the frequency of the returned signal. This variation gives direct and highly accurate measurements of the radial component of a target's velocity relative to the radar.
Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz (GHz) and below. At 300 GHz, the corresponding wavelength is 1 mm ; at 30 Hz the corresponding wavelength is 10,000 km. Like all electromagnetic waves, radio waves in a vacuum travel at the speed of light, and in the Earth's atmosphere at a close, but slightly lower speed. Radio waves are generated by charged particles undergoing acceleration, such as time-varying electric currents. Naturally occurring radio waves are emitted by lightning and astronomical objects, and are part of the blackbody radiation emitted by all warm objects.
Millimeter-wave cloud radars, also denominated cloud radars, are radar systems designed to monitor clouds with operating frequencies between 24 and 110 GHz. Accordingly, their wavelengths range from 1 mm to 1.11 cm, about ten times shorter than those used in conventional S band radars such as NEXRAD.
Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere. As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. Understanding the effects of varying conditions on radio propagation has many practical applications, from choosing frequencies for amateur radio communications, international shortwave broadcasters, to designing reliable mobile telephone systems, to radio navigation, to operation of radar systems.
NEXRAD or Nexrad is a network of 160 high-resolution S-band Doppler weather radars operated by the National Weather Service (NWS), an agency of the National Oceanic and Atmospheric Administration (NOAA) within the United States Department of Commerce, the Federal Aviation Administration (FAA) within the Department of Transportation, and the U.S. Air Force within the Department of Defense. Its technical name is WSR-88D.
Weather radar, also called weather surveillance radar (WSR) and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, and estimate its type. Modern weather radars are mostly pulse-Doppler radars, capable of detecting the motion of rain droplets in addition to the intensity of the precipitation. Both types of data can be analyzed to determine the structure of storms and their potential to cause severe weather.
The King City weather radar station is a weather radar located in King City, Ontario, Canada. It is operated by Environment Canada and is part of the Canadian weather radar network, for which it is the primary research station.
The Canadian weather radar network consists of 31 weather radars spanning Canada's most populated regions. Their primary purpose is the early detection of precipitation, its motion and the threat it poses to life and property.
A lightning detector is a device that detects lightning produced by thunderstorms. There are three primary types of detectors: ground-based systems using multiple antennas, mobile systems using a direction and a sense antenna in the same location, and space-based systems.
ARMOR Doppler weather radar is a C-Band, Dual-Polarimetric Doppler Weather Radar, located at the Huntsville International Airport in Huntsville, Alabama. The radar is a collaborative effort between WHNT-TV and the University of Alabama in Huntsville. Live data for the radar is only available to a limited audience, such as UAH employees and NWS meteorologists. All ARMOR data is archived at the National Space Science and Technology Center located on the UAH campus.
Doppler on Wheels is a fleet of X-band and C-band radar trucks managed by the University of Illinois Urbana-Champaign and previously maintained by the Center for Severe Weather Research (CSWR) in Boulder, Colorado, led by principal investigator (PI) Joshua Wurman, with the funding largely provided by the National Science Foundation (NSF). The DOW fleet and its associated Mobile Mesonets and deployable weather stations (Pods) were Lower Atmospheric Observing Facilities (LAOF) "National Facilities" supporting a wide variety NSF-sponsored research. They are now included in the NSF's "Community Instruments and Facilities" (CIF) program led by PI Karen Kosiba.
The Verification of the Origins of Rotation in Tornadoes Experiment are field experiments that study tornadoes. VORTEX1 was the first time scientists completely researched the entire evolution of a tornado with an array of instrumentation, enabling a greater understanding of the processes involved with tornadogenesis. A violent tornado near Union City, Oklahoma was documented in its entirety by chasers of the Tornado Intercept Project (TIP) in 1973. Their visual observations led to advancement in understanding of tornado structure and life cycles.
Microwave engineering pertains to the study and design of microwave circuits, components, and systems. Fundamental principles are applied to analysis, design and measurement techniques in this field. The short wavelengths involved distinguish this discipline from electronic engineering. This is because there are different interactions with circuits, transmissions and propagation characteristics at microwave frequencies.
The Shared Mobile Atmospheric Research and Teaching Radar, colloquially known as SMART-R or SR, is a mobile Doppler weather radar platform operated and created by University of Oklahoma (OU) with aide from Texas A&M and Texas Tech University in 2001.
The Joint Polarization Experiment (JPOLE) was a test for evaluating the performance of the WSR-88D in order to modify it to include dual polarization. This program was a joint project of the National Weather Service (NWS), the Federal Aviation Administration (FAA), and the US Air Force Meteorological Agency (AFWA), which took place from 2000-2004. It has resulted in the upgrading of the entire meteorological radar network in the United States by adding dual polarization to better determine the type of hydrometeor, and quantities that have fallen.
The present weather sensor (PWS) is a component of an automatic weather station that detects the presence of hydrometeors and determines their type and intensity. It works on a principle similar to a bistatic radar, noting the passage of droplets, or flakes, between a transmitter and a sensor. These instruments in automatic weather stations are used to simulate the observation taken by a human observer. They allow rapid reporting of any change in the type and intensity of precipitation, but include interpretation limitations.
