PowerPoint Sunusu

1
METEOROLOGICAL TARGETS

• TO DETECT STORMS AND OTHER WEATHER PHENOMENA
• SEVERE STORM AND TORNADO WARNINGS, HURRICANE
  OBSERVATIONS, FLOOD WARNINGS AND WINDSHEAR
  WARNINGS SAVING OF LIVES AND POPERTY

CLOUDS
2
Droplets sizes 5 100 ?m
3
The mean droplet size distributions for various
cloud types.
St
As
Cu
(Fletcher, 1966)
4
z generally quite weak
Diameter (?m) Number ND6 (mm6/m3)
5 100 1.56.10-6
10 100 1.00.10-4
15 50 5.69.10-6
20 25 1.60.10-3
25 10 2.44.10-3
30 5 9.19.10-3
35 1 4.01.10-3
Total 1.80.10-2-17.4 dBz
5
Raindrop size dist. 30-40 years
Easly detectable
6
Marshall and Palmer drop-size distributions
compared with the results of Laws and Parsons.
7
The Marshall-Palmer relationsihip is given by
R rainrate in mm/h
Using these,,,,, obtain the number of drops
per unit volume
8
Z-R RELEATIONSHIP
R rainrate in mm/h Z rad. ref. Factor
(mm6/m3) A, b emprical constants
Emprical relationship
Battan (1973) 60 experiments for Z-R
Most commonly used Z-R
(Marshall and Palmer)
9
From 20 dBZ (100 mm6/m3) to 50 dBZ (100 000
mm6/m3)
Z for rain
Z for storms
??75 dBZ
Z for hail
??55 dBZ
NWSs results for rainrate and reflectivitiy
Rainrate (in/h) Reflectivity (dBZ)
0.1 29.5
0.25 39.5
0.5 40.7
1.25 47.0
2.5 51.9
4.0 55.1
10
Easily detectable
Snow and Rain differences
1. Precipitation rate for snow is usually mucc
less than it is for rain. water
equivalent precipitation rate
MOISTURE --- TEMPERATURE
heaviest snows above the melting temp. of
ice, 33 to 36 F
11

• The primary reason snow is not detectable by
  radar is the shallow
• height of typical snow storms.
• Snow storms are usually much lower than most
  rain storms.
• Snow storms are often very widespread in
  area, but they may
• only extend a few thousand meters above
  the surface.
• SNOW IS LESS EASILY DETECTABLE THAN RAIN..

12
HAIL
HAIL A precipitation in the form of ice.
Diameter 5 mm (at least)
85 of thunderstorms contain hail (at least
during part of their lives)
Diameter ranges from 5 mm to 10 cm
Coeffeville, Kansas,
Worlds record hailstone
14 September 1972
14 cm (longest dimension)
13
Terminal Velocity of Hail
Measurements and calculations for Vt
D hailstone diameter (usually in cm) Vt
terminal velocity (in m/s) A an
emprical constant. Measurements for
A 11.45 (Matson and Huggins, 1979)
14
Z from hail depends upon wether the outside
surface is WET or DRY. Dry hail has a lower
reflectivity than wet hail of the same size.
HAILSTONES
MIE REGION
For ?3 cm and 5 cm radars
MIE REGION
For ?10 cm radars
RAYLEIGH REGION
15
DISCUSSIONS
16
(No Transcript)
17
(No Transcript)
18
National Weather Service Doppler Radars
19
Turkish State Meteorological Service Radars
20
SELECTED TOPICS FOR NEXT SEMINAR ARE
21
R E F E R E N C E S (selected)
  Atlas, D., 1990 Radar in Meteorology, Boston,
Amer. Meteor. Soc., 806 pp.   Battan, L. J.,
1973 Radar Observation of the Atmosphere,
Chicago, University of Chicago Press, 324 pp.,
Reprinted by TechBooks, 2600 Seskey Glen Court,
Herndon, VA 22071. Buderi, R., 1996 The
Invention That Changed the World, Simon
Schuster, New York, 575 pp.   Doviak, R. J.
and D. S. Zrnic, , 1993 Doppler Radar and
Weather Observations, Second Edition, San
Diego, AcademicPress, Inc., 562 pp.   Marshall,
J. S. and W. McK. Palmer, 1948 The Distribution
of Raindrops with Size, J. Meteor., 5,
165-166.   Matson, R. and A. W. Huggins, 1979
Field Observations of the Kinematics of
Hailstorms, NCAR/CSD, Boulder, NCAR
/TN-139STR, 68 pp.   Rinehart, R. E., 2001
Radar for Meteorologists, Rinehart Publicatipns,
Columbia, MO, 427 pp.  
22
THANKS