Radar Basics

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Analysis & Diagnosis1

Radar PaletteHome Radar Basics

Radar Basics

How does radar work?

What are the characteristics of all radar systems? What are the characteristics of Canadian radars?

Introduction to the basic radar systems

! Con"entional! Do##ler

! Dual $olari%ed
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TheThe

beambeamof energyof energy

spreads outspreads out

with distance,with distance,

taking a shapetaking a shape

resembling a coneresembling a cone

just like the light beamjust like the light beam

from a coastal lighthouse.from a coastal lighthouse.

ADA '(A)ADA '(A)

ADA '(A)ADA '(A)


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beam

width

beamaxis

First pulse

(pulse(pulse

lengthlengthinin

timetime

!econd pulse

hh (pulse(pulse

lengthlength

inin

spacespace


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Widening 'eamWidening 'eam

Widening 'eamWidening 'eam

BeamwidthBeamwidth("("bb

at a range (rat a range (r

is gi#en by$is gi#en by$

"b% r sin

For small anglesFor small angles

it can beit can be

approximated asapproximated as

"br

200

150

100

50

r


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*acuum +*acuum +

a##ro,imately - . 1/a##ro,imately - . 1/00msms

in a homogeneous mediumin a homogeneous medium

2 straight line2 straight line

2 constant s#eed2 constant s#eed

() Wa"e $ro#agation() Wa"e $ro#agation

() Wa"e $ro#agation() Wa"e $ro#agation

atmos#here not being homogeneousatmos#here not being homogeneous


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Refraction & beam bendingRefraction & beam bending

'bsorption & energy absorption'bsorption & energy absorption

!cattering & beam scattering!cattering & beam scattering

Reflection & beam reflectionReflection & beam reflection

Atmos#heric InteractionsAtmos#heric Interactions

Atmos#heric InteractionsAtmos#heric Interactions


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depends mainly on #ertical refracti#ity gradientdepends mainly on #ertical refracti#ity gradient

assumed straight line propagationassumed straight line propagation

under )normal* conditions$under )normal* conditions$

++ constant standardconstant standardrefracti#e index gradientrefracti#e index gradient

++ constantconstantradius of the earthradius of the earth

adar $ro#agationadar $ro#agationadar $ro#agationadar $ro#agation


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adar (8uationadar (8uationadar (8uationadar (8uation

r

t b b

P P G K

r

h Z=

3 2

2

218

21024 2

10 ln

Pr: average received power (W) Pt: peak transmitted power (W)

ke: pulse length in space (m) G : antenna gain

b : horizontal beam width b : vertical beam width

: transmitted wavelength (m) |K|2: targets re!ractive inde"

r : targets slantrange (m) # : target re!lectivit$ !actor or #e(mm%m&')
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Radar range -uation

non uniform #ertical distribution

+R #ariations

beam filling

Assum#tionsAssum#tionsAssum#tionsAssum#tions


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9im#ler adar (8uation9im#ler adar (8uation9im#ler adar (8uation9im#ler adar (8uation

rP Kr

C Z

=

2

2

where C is the adar Constantwhere C is the adar ConstantK targets refractive index

Z target reflectivity factor

r targets slant range

Pr average received power


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A:);9$H(ICA:);9$H(IC

A::(6


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A'9;$:I;6A'9;$:I;6


A'9;$:I;6A'9;$:I;6

"ater #apor $"ater #apor $

For microwa#es, main absorbing gases are$For microwa#es, main absorbing gases are$

pressurepressure temperature (in#ersetemperature (in#erse

absolute humidityabsolute humidity

2xygen $2xygen $

pressure (s-uaredpressure (s-uared temperaturetemperature

weaker #ariables$weaker #ariables$

+ climate+ climate

+ season+ season

3orrections to the order of 4 to 5 dB (within 677 km3orrections to the order of 4 to 5 dB (within 677 km

can be applied to precipitation measurements.can be applied to precipitation measurements.
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'ttenuation'ttenuation

0RF can theoretically determine0RF can theoretically determinea maximum unambiguous range.a maximum unambiguous range.

8n practice, within a network,8n practice, within a network,

the useful range of weather radarsthe useful range of weather radars

would be less than 677 km.would be less than 677 km.

!pecial re-uirements for long range detection!pecial re-uirements for long range detection

ofthunderstormcan also be ser#iced.ofthunderstormcan also be ser#iced.

9uantitati#e precipitation measurements9uantitati#e precipitation measurements

near the surface can extend to a distance of :47 km.near the surface can extend to a distance of :47 km.

/oppler may expand intrinsic limitations/oppler may expand intrinsic limitationswith new de#elopments.with new de#elopments.


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HydrometeorsHydrometeorsHydrometeorsHydrometeors

attenuation relates to$attenuation relates to$+ shape+ shape

+ si1e+ si1e

+ composition+ composition+ wa#elength$+ wa#elength$

=:7 cm$ rather weak:7 cm$ rather weak

=; cm$ acceptable (higher latitude; cm$ acceptable (higher latitude= 4 cm$ significant4 cm$ significant


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Water massWater massWater massWater mass

larger water masslarger water masscauses more attenuation$causes more attenuation$

ice has less effect than li-uid.ice has less effect than li-uid.

'ttenuation increases in$'ttenuation increases in$+ more dense precipitation areas+ more dense precipitation areas

+ hea#ier precipitation+ hea#ier precipitation


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9i%e9i%e9i%e9i%e


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(ormal propagation

4/3 OF EARTHS

RADIUS

normal atmospheric conditionsnormal atmospheric conditions


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abnormal atmos#heric conditions

subrefraction

superrefraction

ducting

warm dry air aloftcool, moist air below

cool, moist air aloftwarm, dry air below


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TheThe

beambeamof energyof energy

spreads outspreads out

with distance,with distance,

taking a shapetaking a shape

resembling a coneresembling a conejust like the light beamjust like the light beam

from a coastal lighthouse.from a coastal lighthouse.

ADA '(A)ADA '(A)ADA '(A)ADA '(A)


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beam

width

beamaxis

First pulse

(pulse(pulse

lengthlength

inin

timetime

!econd pulse

hh (pulse(pulse

lengthlength

inin

spacespace


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Widening 'eamWidening 'eamWidening 'eamWidening 'eam

BeamwidthBeamwidth

("("bb

at a range (rat a range (r

is gi#en by$is gi#en by$

"b% r sin

For small anglesFor small angles

it can beit can be

approximated asapproximated as

"br

200

150

100

50

r


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*acuum +*acuum +

a##ro,imately - . 1/a##ro,imately - . 1/00msms

in a homogeneous mediumin a homogeneous medium

2 straight line2 straight line

2 constant s#eed2 constant s#eed

() Wa"e $ro#agation() Wa"e $ro#agation() Wa"e $ro#agation() Wa"e $ro#agation

atmos#here not being homogeneousatmos#here not being homogeneous


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Refraction & beam bendingRefraction & beam bending

'bsorption & energy absorption'bsorption & energy absorption

!cattering & beam scattering!cattering & beam scattering

Reflection & beam reflectionReflection & beam reflection

Atmos#heric InteractionsAtmos#heric InteractionsAtmos#heric InteractionsAtmos#heric Interactions


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refracti"e inde,refracti"e inde,

n 3 c un 3 c u

n+ refracti"e inde,n+ refracti"e inde,

c+ lights#eed 4in "acuum5c+ lights#eed 4in "acuum5

u+ lights#eed in mediumu+ lights#eed in medium

Refracti#ity (Refracti#ity (

6 3 4n215 1/6 3 4n215 1/77

efractionefractionefractionefraction


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depends mainly on #ertical refracti#ity gradientdepends mainly on #ertical refracti#ity gradient

assumed straight line propagationassumed straight line propagation

under )normal* conditions$under )normal* conditions$

++ constant standardconstant standardrefracti#e index gradientrefracti#e index gradient

++ constantconstantradius of the earthradius of the earth

adar $ro#agationadar $ro#agationadar $ro#agationadar $ro#agation


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adar (8uationadar (8uationadar (8uationadar (8uation

r

t b b

P P G Kr

h Z=

3 2

2

218

21024 2

10 ln

Pr: average received power (W) Pt: peak transmitted power (W)

ke: pulse length in space (m) G : antenna gain

b : horizontal beam width b : vertical beam width

: transmitted wavelength (m) |K|2: targets re!ractive inde"

r : targets slantrange (m) # : target re!lectivit$ !actor or #e(mm%m&')
http://radarpalette-storyboardcms.ppt/http://radarpalette-storyboardcms.ppt/http://radarpalette-storyboardcms.ppt/http://radarpalette-storyboardcms.ppt/http://radarpalette-storyboardcms.ppt/http://radarpalette-storyboardcms.ppt/http://radarpalette-storyboardcms.ppt/http://radarpalette-storyboardcms.ppt/http://radarpalette-storyboardcms.ppt/http://radarpalette-storyboardcms.ppt/http://radarpalette-storyboardcms.ppt/http://radarpalette-storyboardcms.ppt/


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Radar range -uation

non uniform #ertical distribution

+R #ariations beam filling

Assum#tionsAssum#tionsAssum#tionsAssum#tions


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9im#ler adar (8uation9im#ler adar (8uation9im#ler adar (8uation9im#ler adar (8uation

rPK

r

C Z

=

2

2

where C is the adar Constantwhere C is the adar ConstantK targets refractive index

Z target reflectivity factor

r targets slant range

Pr average received power


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!ampling Reflecti#ity!ampling Reflecti#ity

/imensions of #olume elements being scanned/imensions of #olume elements being scanned

are determined by the beam widths and pulse length.are determined by the beam widths and pulse length.

Beam width is associated with the e-uipment$Beam width is associated with the e-uipment$

0ulse length affects the si1e of0ulse length affects the si1e of

conical section being sensed.conical section being sensed.

b

antennaD

=

70


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A::(6


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A'9;$:I;6A'9;$:I;6


A'9;$:I;6A'9;$:I;6

"ater #apor $"ater #apor $

For microwa#es, main absorbing gases are$For microwa#es, main absorbing gases are$

pressurepressure temperature (in#ersetemperature (in#erse

absolute humidityabsolute humidity

2xygen $2xygen $

pressure (s-uaredpressure (s-uared temperaturetemperature

weaker #ariables$weaker #ariables$

+ climate+ climate+ season+ season

3orrections to the order of 4 to 5 dB (within 677 km3orrections to the order of 4 to 5 dB (within 677 km

can be applied to precipitation measurements.can be applied to precipitation measurements.

' i


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'ttenuation'ttenuation

0RF can theoretically determine0RF can theoretically determine

a maximum unambiguous range.a maximum unambiguous range.

8n practice, within a network,8n practice, within a network,

the useful range of weather radarsthe useful range of weather radars

would be less than 677 km.would be less than 677 km.

!pecial re-uirements for long range detection!pecial re-uirements for long range detection

ofthunderstormcan also be ser#iced.ofthunderstormcan also be ser#iced.

9uantitati#e precipitation measurements9uantitati#e precipitation measurements

near the surface can extend to a distance of :47 km.near the surface can extend to a distance of :47 km.

/oppler may expand intrinsic limitations/oppler may expand intrinsic limitationswith new de#elopments.with new de#elopments.


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HydrometeorsHydrometeorsHydrometeorsHydrometeors

attenuation relates to$attenuation relates to$+ shape+ shape

+ si1e+ si1e

+ composition+ composition+ wa#elength$+ wa#elength$

=:7 cm$ rather weak:7 cm$ rather weak

=; cm$ acceptable (higher latitude; cm$ acceptable (higher latitude= 4 cm$ significant4 cm$ significant


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Water massWater massWater massWater mass

larger water masslarger water masscauses more attenuation$causes more attenuation$

ice has less effect than li-uid.ice has less effect than li-uid.

'ttenuation increases in$'ttenuation increases in$+ more dense precipitation areas+ more dense precipitation areas

+ hea#ier precipitation+ hea#ier precipitation


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9i%e9i%e9i%e9i%e


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(ormal propagation

4/3 OF EARTHS

RADIUS

normal atmospheric conditionsnormal atmospheric conditions


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abnormal atmos#heric conditions

subrefraction

superrefraction

ducting

warm dry air aloftcool, moist air below

cool, moist air aloftwarm, dry air below

Warm rontal Cross2section along'


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Analysis & Diagnosis>/


WC'

CC'

Warm rontal Cross2section along

@eading 'ranch of the Warm Con"eyor

'elt 4WC'5

Cold air in Cold Con"eyor 'elt 4CC'5 dee# and dry

)oist #ortion of Warm Con"eyor 'elt 4WC'5 is high and "eered from frontal #er#endicular ! katabatic tendency

Dry lower le"els of WC' originate from ahead of the system and backed from frontal #er#endicular

)i,ing

Aone9urface

Warm ront

rontal slo#e is more shallow than the ty#ical 1+B//

$reci#itation e,tends e8uidistant into the unmodified CC'

$reci#itation e,tends further into the moistened modified CC'

Increasing CC'

)oistening

WC'orient

edfor

ma,imumfro

ntallift

WC'

orient

edfor

lessfron

tallift

*irga$rec

i#itation

@ower

Hydrometeor

Density

Common location for "irga A

' B

WC' ty#ically "eers with height 4it is after all a warm front5

@ink to Classic

(,am#le

>ertical /eformation one /istribution and the 3B


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Analysis & Diagnosis>1




@nder "3B

*irga only likely on the leading edge of the WC'

:he CC' is becoming increasingly moist rontal o"errunning and isentro#ic lift is

increasing thus increasing the intensity of the

#reci#itation #rocess

Warm front becoming more likely Anabatic

Click for the Conce#tual )odel and (,#lanation

Warm rontal Cross2section along'


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Analysis & DiagnosisF/


WC'

CC'

g

Central 'ranch of the Warm Con"eyor

'elt 4WC'5

Cold air in Cold Con"eyor 'elt 4CC'5 more shallow and moist

)oist #ortion of Warm Con"eyor 'elt 4WC'5 is thicker higher and #er#endicularto front

@ower le"els of WC' ha"e the same origin as the u##er le"el of the WC' 2 frontal #er#endicular

)i,ingA

one

9urface

Warm ront

rontal slo#e is near the ty#ical 1+B//

$reci#itation e,tends further into the moistened modified CC'

Hori%ontal rain area begins to e,#and as CC' moistens

Increasing CC'

)oistening

WC'o

riented

for

ma,imu

mfronta

llift

*irga$rec

i#itation

@ower

Hydrometeor

Density

Common location for "irgaA

' B

WC' shows little directional shift with height A greater WC' de#th is frontal #er#endicular

$reci#itation

At 9urface



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Analysis & DiagnosisF1




Behind "3B

Behind "3B


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Analysis & Diagnosis7F


Behind "3B

Behind "3B


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Analysis & Diagnosis77


Behind "3B

Behind "3B


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Analysis & Diagnosis7G


Behind "3B

Behind "3B


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Analysis & Diagnosis70Radar PaletteHome Radar Basics

Behind "3B

This must be and remain as !lide 4:.


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This must be and remain as !lide 4:.

:he links to the three sections of the airflows

that com#rise each of the con"eyor belts arelocated at 9lide 111 and B1

9lide 11 is always the central col limited

circulation

:his lea"es 1/ $ower$oint slides for thede"elo#ment of the training material which

should be more than ade8uate

Radar Basics

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