radar meteorology yrd. doç. dr. ali denİz. outline introduction radar hardware electromagnetİc...
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RADAR METEOROLOGY RADAR METEOROLOGY
Yrd. Doç. Dr. Ali DENİZYrd. Doç. Dr. Ali DENİZ
OUTLINE
INTRODUCTION
RADAR HARDWARE
ELECTROMAGNETİC WAVES
RADAR EQUATION FOR POINT TARGETS
METEOROLOGICAL TARGETS
DISCUSSIONS
REFERENCES
RAdio Detection And Ranging
LIght Detection And Rangingwawelength
RADIO RADAR
Buderi – 1996 : THE INVENTION THAT CHANGED THE WORLD
Young and Taylor – 1934 : PULSES OF ENERGY
INTRODUCTION
Doppler Radars
power
speed
Kısayol Bilgisayarım.lnk
RADAR DATA AUTOMATIC WARNINGS
POLARIZATION
KINDS
SHAPES
SIZES
RADAR HARDWARERADAR HARDWARE
reflector
transmitter
modulator
Master Clock
receiver
display
antenna
waveguideduplexer
How Does Radar Work?How Does Radar Work?
single antennatarget
short pulses of energysend
Return back
The antenna rotates about a vertical axis, scanning the horizon in all directions
To determine how high a storm is, met. radars can also aim their antennas above the horizon
Whole cycle10 to 20 elevation angles
+ 4 to 6 minutes
DATA ...DISPLAY
TYPES OF RADARSTYPES OF RADARS
Monostatic and Bistatic radar
CW and pulsed radar
Doppler radarFM-CW radar
Wind profilers and aircraft radars
Airborn radar
Shipboard radar
Weather radar
Dual-wavelength radar
Polarization-diversity radar
RADARS USED IN AVIATIONRADARS USED IN AVIATION
ARSRARSR ::
ASRASR ::
TDWRTDWR ::
ARDEARDE ::
L-band, =20 cmDetect aircraft
Provide information on the position of aircrafts
Detect microbursts, gustfronts, wind shifts, pecipitaion
Follow aircraft on the ground at some airports
ELECTRO-MAGNETIC WAVESELECTRO-MAGNETIC WAVES
Radio & radar electro-magnetic radiation
c
f f : 1 Hz=1 cycle / secondc: m/s: m
Elektromagnetic spectrum
Skolnik, 1980.
Radar bands and corresponding frequency bands, (Rinehart, 2001).
Radar Bands Frequency Wavelength
HF 3-30 MHz 100-10 m
VHF 30-300 MHz 10-1 m
UHF 300-1000 MHz 1-0.3 m
L 1-2 GHz 30-15 cm
S 2-4 GHz 15-8 cm
C 4-8 GHz 8-4 cm
X 8-12 GHz 4-2.5 cm
Ku 12-18 GHz 2.5-1.7 cm
K 18-27 GHz 1.7-1.2 cm
Ka 27-40 GHz 1.2-0.75 cm
mm or W 40-300 GHz 7.5-1 mm
REFRACTIVE INDEXREFRACTIVE INDEX
u
cn
c : the speed of light in a vacuumu: the speed of light in a mediumn: refractive index
cu (always) n1 (unitless parameter)
Actually, it has two components ; iknm 1i
k Absorption of coefficient of the medium
For air; m=1.003
REFRACTIVITY [N]
2710.03.44810
6.77
f
N
T
eP
TN e
Atm. Press. (mb, hPa)
Temp. (°K)
Vap. Press. (mb, hPa)
Num. of free electron / m3
Freq. of the radar (Hz.)
Under normal atmospheric contions;
Ground N
Z N
RADAR EQUATION FOR POINT TARGETRADAR EQUATION FOR POINT TARGET
radar storms Rainrate and ...
radar Puls of energy into space by antenna
Power A spherically expanding shell of energy
24 rArea r : the range from the radar
Power density : S24 r
PS t
24 r
gAPP t
P The power intercepted bye the target
target
The amount of energy detected by radar will be:
24
.
r
APP e
r
424
...
r
AAgPP et
r
4π
gλA
2
e
Ae : The effective area of the receiving antenna
43
22
64
..
r
AgPP t
r
New!
THE BACK-SCATTERINGTHE BACK-SCATTERING CROSS-SECTIONALCROSS-SECTIONAL
AREA OF THE TARGETAREA OF THE TARGET
A
Final FormFinal Form43
22
64
..
r
gPP t
r
SPHERICAL TARGETSSPHERICAL TARGETS
A sphere is LARGE 2r “Large” : 10/ D
A sphere is SMALLRAYLEIGH
region “Small” : 1.0/ D
In the Rayleigh region :4
625
DK
2K :: related to the complex index of refraction of the material
Meteorological targets small RAYLEIGH REGION MET. RADAR USE
SOME STANDART POINT TARGETS :Spheres, birds, aircraft, buildings, water towers and radio towers....
In conclusion;
Point targets are imp. source of echo for many radars. By making careful measurements of the return from point targets, much canbe learned about the targets. Well-chosen point targets also make it possible to monitor the
health and quantitative reliability of a particular radar system.
(Battan, 1973)