1f. Doppler RadarJust as we are able to distinguish different colors
of light by their wavelengths, so can we differentiate sounds by the
length of their sound waves. If an object making a sound is moving away
from a listener, the sound waves are stretched out and assume a lower
pitch. Sound waves are compressed when an object moves toward the
listener, making them higher pitched. Unconsciously, we use this
principle, calledthe Doppler effect, to determine whether an ambulance
siren is coming closer or moving away, If the pitch of the siren seems
to become higher, we know the ambulance is getting nearer (of course,
the siren would also sound louder). A similar process occurs when
electromagnetic waves are reflected by a moving object The light shifts
to shorter wavelengths when reflected by an object moving toward the
receiver and to longer wavelengths as it bounces off an object moving
away from the receiver.Applying the Doppler EffectDoppler radar is a
type of radar system that takes advantage of this principle. It allows
the user to observe the movement of raindrops and ice particles (and
thus determine wind speed and direction) from the shift in wavelength of
the radar waves, as well as the intensity of precipitation. Like any
other type of radar, Doppler radar has a transmitter that emits pulses
of electromagnetic energy with wavelengths on the order of several
centimeters. Depending on the wavelength used, water droplets and snow
crystals above certain critical sizes reflect a portion of the radar’s
electromagnetic energy back to the transmitter/receiver. In the case of
particularly violent tornadoes that pick up large objects from the
ground, the radar will observe this airborne material and display it as a
debris ball.Doppler radar is special in its ability to observe the
motion of the cloud constituents. If a cloud droplet is moving away from
the radar unit, the wavelength of the beam is slightly elongated as it
bounces off the reflector. Such reflections are normally indicated on
the display monitor as reddish to yellow. Likewise, a droplet moving
toward the radar unit undergoes a shortening of the wavelength. Echoes
from these constituents are displayed as blue or green on the radar
screen.Radar ScansA radar unit must rotate 360 degrees to get a complete
picture of the weather situation surrounding the transmitter/receiver
unit. When the transmitter makes one complete rotation at a fixed angle,
it is said to have completed a sweep. The angle can then be increased
as a second sweep is taken that depicts a higher cloud level. This can
be repeated several times so that the radar can peer into multiple
levels of the cloud. The compilation of all the individual sweeps takes
approximately 5 to 10 minutes and produces a volume sweep.Figure 11-4-1
shows a pair of Doppler radar images of a major storm near Dallas-Fort
Worth, Texas, on March 29, 2000. Figure 11-4-1a shows the reflectivity
of the storm, with redder regions indicating intense precipitation and
green areas representing less intense precipitation. The white arrows
point toward a hook echo (described in the main text of this chapter).
Figure 11-4-1b displays the storm radial velocity (SRV) pattern, which
describes the motions taking place within the cloud. SRV displays use
redder colors to represent winds blowing away from the radar and green
to indicate movement toward the radar, The yellow arrows on this image
highlight a region of counterclockwise rotation, As we discuss later in
the chapter, this pattern, called a mesocyclone, sometimes precedes the
formation of a tornado. After the onset of rotation, it takes only 30
minutes or so for the tornado to form, which allows meteorologists to
give warnings in advance. In this particular case, a tornado did hit the
city of Fort Worth. A study published in 2005 concluded that the
implementation of Doppler radar units across the United States has
prevented 79 fatalities and 1050 injuries per year. Doppler radar has
increased the average warning time for all tornadoes to 13 minutes.
Prior to Doppler radar, warnings typically did not go out until 4
minutes after touchdown.MapMasterNorth America Physical Environment
Doppler Radar Sites (U.S.)The NEXRAD NetworkToday about 160 Doppler
sites are scattered across the United States as part of the NEXRAD
network (Figure 11-4-2). The National Weather Service operates 113 of
these sites; the rest are owned by the Federal Aviation Administration
and the Department of Defense. In part because of budgetary cutbacks,
the Atmospheric Environment Service of Canada has just a handful of
Doppler radar installations. Because both sides of the border area tend
to be heavily populated, Doppler radar from the United States provides
extensive coverage of severe storms that could affect many large
Canadian urban centers.NEXRAD is also useful for flood forecasting,
providing continual precipitation estimates over large areas. Doppler
radar can sometimes observe wind movements even when no clouds exist, as
large clusters of flying bugs or heavy dust concentration scatter radar
waves back toward the transmitter. The resultant echoes are called
clear air echoes.Just as the introduction of Doppler radar represented a
major breakthrough for monitoring severe weather, the introduction of
dual-polarization technology (Chapter 7) marks a revolutionary
breakthrough for forecasting. Unlike earlier versions of Doppler radar,
dual-polarization radar gives information about both the vertical and
horizontal dimensions of ice particles and water droplets in clouds,
thus allowing a better identification of hail. in addition, it is
particularly useful for identifying flying tornado debris, allowing more
precise identification of the location and movement of
tornadoes.Portable Doppler RadarThe NEXRAD network of Doppler radar,
installed primarily for forecasting purposes, provides information on
tornadoes that has proven useful to researchers. But NEXRAD radar units
are spaced too far apart to provide close scrutiny of most passing
tornadoes, so researchers have looked to transportable radar to observe
tornadoes at close range. For this reason, tornado researchers have come
to rely on portable Doppler radar units called Doppleron wheels that
have units mounted to a flatbed truck (Figure 11-4-3) These units have
been instrumental in acquiring new information on tornado
dynamics.FIGURE 11-4-1 Doppler Radar Images. A storm near Dallas–Fort
Worth. Texas, on March 29, 2000. Part (a) depicts the intensity of
precipitation; part (b) shows the storm radial velocity (SRV) pattern,
which is the movement of different parts of the storm toward or away
from the radar unit....FIGURE 11-4-2 Doppler Radar Sites in the United
States.......What is the guiding principle behind Doppler radar? Get solution
2f. Doppler RadarJust as we are able to distinguish different colors of light by their wavelengths, so can we differentiate sounds by the length of their sound waves. If an object making a sound is moving away from a listener, the sound waves are stretched out and assume a lower pitch. Sound waves are compressed when an object moves toward the listener, making them higher pitched. Unconsciously, we use this principle, calledthe Doppler effect, to determine whether an ambulance siren is coming closer or moving away, If the pitch of the siren seems to become higher, we know the ambulance is getting nearer (of course, the siren would also sound louder). A similar process occurs when electromagnetic waves are reflected by a moving object The light shifts to shorter wavelengths when reflected by an object moving toward the receiver and to longer wavelengths as it bounces off an object moving away from the receiver.Applying the Doppler EffectDoppler radar is a type of radar system that takes advantage of this principle. It allows the user to observe the movement of raindrops and ice particles (and thus determine wind speed and direction) from the shift in wavelength of the radar waves, as well as the intensity of precipitation. Like any other type of radar, Doppler radar has a transmitter that emits pulses of electromagnetic energy with wavelengths on the order of several centimeters. Depending on the wavelength used, water droplets and snow crystals above certain critical sizes reflect a portion of the radar’s electromagnetic energy back to the transmitter/receiver. In the case of particularly violent tornadoes that pick up large objects from the ground, the radar will observe this airborne material and display it as a debris ball.Doppler radar is special in its ability to observe the motion of the cloud constituents. If a cloud droplet is moving away from the radar unit, the wavelength of the beam is slightly elongated as it bounces off the reflector. Such reflections are normally indicated on the display monitor as reddish to yellow. Likewise, a droplet moving toward the radar unit undergoes a shortening of the wavelength. Echoes from these constituents are displayed as blue or green on the radar screen.Radar ScansA radar unit must rotate 360 degrees to get a complete picture of the weather situation surrounding the transmitter/receiver unit. When the transmitter makes one complete rotation at a fixed angle, it is said to have completed a sweep. The angle can then be increased as a second sweep is taken that depicts a higher cloud level. This can be repeated several times so that the radar can peer into multiple levels of the cloud. The compilation of all the individual sweeps takes approximately 5 to 10 minutes and produces a volume sweep.Figure 11-4-1 shows a pair of Doppler radar images of a major storm near Dallas-Fort Worth, Texas, on March 29, 2000. Figure 11-4-1a shows the reflectivity of the storm, with redder regions indicating intense precipitation and green areas representing less intense precipitation. The white arrows point toward a hook echo (described in the main text of this chapter). Figure 11-4-1b displays the storm radial velocity (SRV) pattern, which describes the motions taking place within the cloud. SRV displays use redder colors to represent winds blowing away from the radar and green to indicate movement toward the radar, The yellow arrows on this image highlight a region of counterclockwise rotation, As we discuss later in the chapter, this pattern, called a mesocyclone, sometimes precedes the formation of a tornado. After the onset of rotation, it takes only 30 minutes or so for the tornado to form, which allows meteorologists to give warnings in advance. In this particular case, a tornado did hit the city of Fort Worth. A study published in 2005 concluded that the implementation of Doppler radar units across the United States has prevented 79 fatalities and 1050 injuries per year. Doppler radar has increased the average warning time for all tornadoes to 13 minutes. Prior to Doppler radar, warnings typically did not go out until 4 minutes after touchdown.MapMasterNorth America Physical Environment Doppler Radar Sites (U.S.)The NEXRAD NetworkToday about 160 Doppler sites are scattered across the United States as part of the NEXRAD network (Figure 11-4-2). The National Weather Service operates 113 of these sites; the rest are owned by the Federal Aviation Administration and the Department of Defense. In part because of budgetary cutbacks, the Atmospheric Environment Service of Canada has just a handful of Doppler radar installations. Because both sides of the border area tend to be heavily populated, Doppler radar from the United States provides extensive coverage of severe storms that could affect many large Canadian urban centers.NEXRAD is also useful for flood forecasting, providing continual precipitation estimates over large areas. Doppler radar can sometimes observe wind movements even when no clouds exist, as large clusters of flying bugs or heavy dust concentration scatter radar waves back toward the transmitter. The resultant echoes are called clear air echoes.Just as the introduction of Doppler radar represented a major breakthrough for monitoring severe weather, the introduction of dual-polarization technology (Chapter 7) marks a revolutionary breakthrough for forecasting. Unlike earlier versions of Doppler radar, dual-polarization radar gives information about both the vertical and horizontal dimensions of ice particles and water droplets in clouds, thus allowing a better identification of hail. in addition, it is particularly useful for identifying flying tornado debris, allowing more precise identification of the location and movement of tornadoes.Portable Doppler RadarThe NEXRAD network of Doppler radar, installed primarily for forecasting purposes, provides information on tornadoes that has proven useful to researchers. But NEXRAD radar units are spaced too far apart to provide close scrutiny of most passing tornadoes, so researchers have looked to transportable radar to observe tornadoes at close range. For this reason, tornado researchers have come to rely on portable Doppler radar units called Doppleron wheels that have units mounted to a flatbed truck (Figure 11-4-3) These units have been instrumental in acquiring new information on tornado dynamics.FIGURE 11-4-1 Doppler Radar Images. A storm near Dallas–Fort Worth. Texas, on March 29, 2000. Part (a) depicts the intensity of precipitation; part (b) shows the storm radial velocity (SRV) pattern, which is the movement of different parts of the storm toward or away from the radar unit....FIGURE 11-4-2 Doppler Radar Sites in the United States.......Explain how the use of Doppler radar allows forecasters to provide early warnings of tornado development. Get solution
2f. Doppler RadarJust as we are able to distinguish different colors of light by their wavelengths, so can we differentiate sounds by the length of their sound waves. If an object making a sound is moving away from a listener, the sound waves are stretched out and assume a lower pitch. Sound waves are compressed when an object moves toward the listener, making them higher pitched. Unconsciously, we use this principle, calledthe Doppler effect, to determine whether an ambulance siren is coming closer or moving away, If the pitch of the siren seems to become higher, we know the ambulance is getting nearer (of course, the siren would also sound louder). A similar process occurs when electromagnetic waves are reflected by a moving object The light shifts to shorter wavelengths when reflected by an object moving toward the receiver and to longer wavelengths as it bounces off an object moving away from the receiver.Applying the Doppler EffectDoppler radar is a type of radar system that takes advantage of this principle. It allows the user to observe the movement of raindrops and ice particles (and thus determine wind speed and direction) from the shift in wavelength of the radar waves, as well as the intensity of precipitation. Like any other type of radar, Doppler radar has a transmitter that emits pulses of electromagnetic energy with wavelengths on the order of several centimeters. Depending on the wavelength used, water droplets and snow crystals above certain critical sizes reflect a portion of the radar’s electromagnetic energy back to the transmitter/receiver. In the case of particularly violent tornadoes that pick up large objects from the ground, the radar will observe this airborne material and display it as a debris ball.Doppler radar is special in its ability to observe the motion of the cloud constituents. If a cloud droplet is moving away from the radar unit, the wavelength of the beam is slightly elongated as it bounces off the reflector. Such reflections are normally indicated on the display monitor as reddish to yellow. Likewise, a droplet moving toward the radar unit undergoes a shortening of the wavelength. Echoes from these constituents are displayed as blue or green on the radar screen.Radar ScansA radar unit must rotate 360 degrees to get a complete picture of the weather situation surrounding the transmitter/receiver unit. When the transmitter makes one complete rotation at a fixed angle, it is said to have completed a sweep. The angle can then be increased as a second sweep is taken that depicts a higher cloud level. This can be repeated several times so that the radar can peer into multiple levels of the cloud. The compilation of all the individual sweeps takes approximately 5 to 10 minutes and produces a volume sweep.Figure 11-4-1 shows a pair of Doppler radar images of a major storm near Dallas-Fort Worth, Texas, on March 29, 2000. Figure 11-4-1a shows the reflectivity of the storm, with redder regions indicating intense precipitation and green areas representing less intense precipitation. The white arrows point toward a hook echo (described in the main text of this chapter). Figure 11-4-1b displays the storm radial velocity (SRV) pattern, which describes the motions taking place within the cloud. SRV displays use redder colors to represent winds blowing away from the radar and green to indicate movement toward the radar, The yellow arrows on this image highlight a region of counterclockwise rotation, As we discuss later in the chapter, this pattern, called a mesocyclone, sometimes precedes the formation of a tornado. After the onset of rotation, it takes only 30 minutes or so for the tornado to form, which allows meteorologists to give warnings in advance. In this particular case, a tornado did hit the city of Fort Worth. A study published in 2005 concluded that the implementation of Doppler radar units across the United States has prevented 79 fatalities and 1050 injuries per year. Doppler radar has increased the average warning time for all tornadoes to 13 minutes. Prior to Doppler radar, warnings typically did not go out until 4 minutes after touchdown.MapMasterNorth America Physical Environment Doppler Radar Sites (U.S.)The NEXRAD NetworkToday about 160 Doppler sites are scattered across the United States as part of the NEXRAD network (Figure 11-4-2). The National Weather Service operates 113 of these sites; the rest are owned by the Federal Aviation Administration and the Department of Defense. In part because of budgetary cutbacks, the Atmospheric Environment Service of Canada has just a handful of Doppler radar installations. Because both sides of the border area tend to be heavily populated, Doppler radar from the United States provides extensive coverage of severe storms that could affect many large Canadian urban centers.NEXRAD is also useful for flood forecasting, providing continual precipitation estimates over large areas. Doppler radar can sometimes observe wind movements even when no clouds exist, as large clusters of flying bugs or heavy dust concentration scatter radar waves back toward the transmitter. The resultant echoes are called clear air echoes.Just as the introduction of Doppler radar represented a major breakthrough for monitoring severe weather, the introduction of dual-polarization technology (Chapter 7) marks a revolutionary breakthrough for forecasting. Unlike earlier versions of Doppler radar, dual-polarization radar gives information about both the vertical and horizontal dimensions of ice particles and water droplets in clouds, thus allowing a better identification of hail. in addition, it is particularly useful for identifying flying tornado debris, allowing more precise identification of the location and movement of tornadoes.Portable Doppler RadarThe NEXRAD network of Doppler radar, installed primarily for forecasting purposes, provides information on tornadoes that has proven useful to researchers. But NEXRAD radar units are spaced too far apart to provide close scrutiny of most passing tornadoes, so researchers have looked to transportable radar to observe tornadoes at close range. For this reason, tornado researchers have come to rely on portable Doppler radar units called Doppleron wheels that have units mounted to a flatbed truck (Figure 11-4-3) These units have been instrumental in acquiring new information on tornado dynamics.FIGURE 11-4-1 Doppler Radar Images. A storm near Dallas–Fort Worth. Texas, on March 29, 2000. Part (a) depicts the intensity of precipitation; part (b) shows the storm radial velocity (SRV) pattern, which is the movement of different parts of the storm toward or away from the radar unit....FIGURE 11-4-2 Doppler Radar Sites in the United States.......Explain how the use of Doppler radar allows forecasters to provide early warnings of tornado development. Get solution
