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)