Course Summary

1- Historical Overview: Development of radar through the decades (1940-2000)

2- Radar System: Hardware, characteristics of radar signal, wavelength, refraction, attenuation, reflectivity

factor and rainfall rate.

3- Radar Products: Scanning strategy, resolution, PPI, CAPPI, Forecasts, VIL, GUST,

Accumulations, Vertical Cross-sections.

4- Echo Structures: Dynamical and microphysical processes, precipitation types (meteorological

and non-meteorological), melting layer.

Course Summary (cont.)

5- Doppler Radar: Principle and limitations, interpretation of images, rotation and divergence.

6A- Precipitation Measurements: Methods and errors, Elimination of ground clutter (normal and AP).

B- Vertical Profile of Reflectivity: Scale dependence of errors due to the VPR.

7- Severe Weather: Characteristics of mesocyclones and of VIL maps, (diurnal, yearly and geographical distributions).

8- Polarization: Concept, usefulness in rainfall measurements and target identification.

ACKNOWLEDGEMENTS

Frederic Fabry: Devised the course and provided most of the figures

GyuWon Lee: Helped in preparing some of the PPT presentations

Isztar Zawadzki: For directing innovative research at the McGill Radar

in the past 12 years on which much of this course is based.

Alamelu Kilambi (Computer Scientist) and

Abnash Singh (Electronic Engineer) for implementing those ideas.

On a clear day, only the stationary ground echoes and airplanes weredetected.

RADAR: RAdio Detection And RangingPre-WW2: -Based on theoretical work by Rayleigh(1871), Mie(1908), Ryde (1941-1946). -The potential of radars to detect approaching boats and airplanes is realized. -First radar systems built (looked like tall radio towers, because of long wavelength)

WW2: - Efforts to make radars smaller (transportable on aircraft) - Development of the cavity magnetron by the British (powers all microwave ovens, permitted higher frequencies, shorter wavelength, hence better sensitivity).

Aircraft in Rain

Precipitation is detected for the first time by radar (MIT: Feb, 1941).

Animation sequence showing airplane (point target) landing at Montreal airportShort range (48 km), low elevation (2.2°) radar images every 20 seconds

Late 1940s: Research groups in radar meteorology appear at a few universities

(McGill, MIT...) in order to see precipitation rather than enemy aircraft

Mie, Rayleigh

Mie, Rayleigh

CAPPI

Signal FluctuationsAttenuation, Hail

Snow generationHail studies

Z=200R1.6

VPR

1950s: First radars used operationally for routine weather surveillance by civilian weather services (as opposed to by the army)

Following several years of severehurricane landfalls, the first nationalnetwork of radars is set up in the USA

On the right, Hurricane Alice viewedby a military radar (1st Jan. 1955)

1968: The present McGill radar facility is inaugurated

30 km west of Montreal10-cm wavelength (S-band)9-m diameter antenna on a 30 m tower (enclosed in a fiberglass radome)0.86° beam widthPeak Power: 750 KW24 elevation angles in 5 minutes (6 rpm)480 km range

McGill PPHI (Plan Position with Height Indicator)

120 nm

Analog CAPPI

(Made possible by the 24 elevation angles. This CAPPI provided 2-D as well as 3-D information)

Height: 10000 ft (~ 3 km)Range: 120 nm (~220 km)Available every 5 minutesEach ring represents a heightof 5000 ft along that azimuth

9-Jul-81

12:45

14:45

13:50

15:45

Mid 1970s: Development of fast digitizers and of cheaper computers enables the digital processing of radar data unto magnetic tapes. Extrapolation forecasts are possible.

BUT computer memory is limited to only 32 K bytes (not Geg) and disk storage to only 2.5 Mb.Therefore, only coarse resolution digital maps could be processed:Ex: (64 by 100) array (4.8 km x 7.5 km)

1620 GMT 2-Jul-1975

240 km

1980s: Doppler technology (developed in the 1960s) becomes more commonplace in research radars. McGill radar dopplerized in 1993.

(24 simultaneous reflectivity and Doppler scans every 5 minutes)

Mid 1990s: First Doppler radar network in the USA: 160+ radars 1998-2004: Upgrade of Canadian radar network to 31 Doppler radars

Dual polarization radar operational at McGill

A radar installation is nolonger like an isolatedisland, but part of a radarnetwork.

U.S. RADAR COMPOSITE

Why radar as an operational meteorological instrument ?

Historically, radar filled a gap between

-synoptic scale observations (103 km)

(surface stations every few hundred km making hourly measurements,or radiosondes every 12 hours, or satellite imges every 15-30 minutes)

RADAR (102 km) (Typically 400 km by 400 km)

-local scale observations (10 km)(few kilometers what an observer can see by looking outside).

- Radar is one of the few instruments that can obtain information in three dimensions as a function of time, Pradar = f(x,y,z,t). It can see within storms, and can be used to assess their severity using reflectivity information (how much rain is associated) as well as Doppler velocity information (what are the winds within the storm).

- A radar observation does not disturb the medium in which it is taken

- Most importantly, this information is available immediately at a fine space and temporal resolution (typically 1 to 2 km and 5 to 10 minutes) over large areas (continent-wide when combined in a radar network)

Continental or synoptic scale103 km

Regional scale102 km

IR Loop: 3-4 Feb, 2003

National Radar Composite Loop: 3-4 Feb, 2003

Radars and satellite based imagery have different strengths and complement each other. (Clouds from satellite precede radar echoes). Radars have become the standard instrument for detecting and tracking rapidly developing thunderstorms. Severe weather warning are issued mainly on the basis of radar imagery

Overlapping Radar and Satellite Images

960 km

RAINSAT: RRate = f (Visible, IR)

Proper understanding of radar data requires basic knowledge of propagation, scattering and of the meteorological processes and phenomena.