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Application of DualPolarization Weather Doppler Radar
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Purcell. Wind Profiler. Sulphur. Upper-soundings. KOKC. Upper ... Strong Zh observed NE and SW of Purcell. NE: parameters except Zh are weak. small rains ... – PowerPoint PPT presentation
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Title: Application of DualPolarization Weather Doppler Radar
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Application of Dual-Polarization Weather Doppler
Radar
- Michihiro Teshiba
- SEC Rm 1458
- teshiba_at_ou.edu
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Objective of my study
- Examine the detailed structure of gust front by
using a wind profiler - Typical gust front
- Downdraft caused by evaporative cooling and
precipitation drag - Dense air (downdraft) spreads out along the
ground - A gust front causes at the leading edge of the
outflow - Problems are
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Cont. Objective
- Does a gust front have such a simple structure?
- Are simple arrows enough to explain the
structure? - Dont we know the detailed structure due to the
insufficient data resolutions (observation
simulation)? - A wind profiler has good range and time
resolutions rather than a weather Doppler radar - To compare the data between a wind profiler and
KOUN weather Doppler radar
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As an Introduction of my study
- Introduction of myself (within 1 min.)
- Introduction of dual-polarization weather Doppler
radar - Technical terms
- Meteorological terms
- Preliminary results about a cold front
- KOUN Doppler radar
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Introduce myself
- I had studied on meso-scale convective systems
observed with a wind profiler - Near a Baiu-Meiyu front (MC)
- Typhoon-Tropical Cyclone (BC, Ph.D)
- I have some licenses in Japan of
- Weather forecaster
- Driver licenses of track, bus, trailer (no
limitation) - I often played baseball and softball
- I love cats and fighting fish (betta) !
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What a Dual-pol Radar can examine?
- By parameters obtained by a dual-pol radar
- Size and shapes of hydrometeors
- Distributions of rain, hail, graupel, etc
- Distributions of rain rates and amounts
- Forecasting of lightning (in future)
- position, frequency, and strength
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Equilibrium shapes of rain particles
Bringi et al. (2003) How a rain particle in 5mm
diameter oscillate.
- To define rain shape
- Surface tension
- Hydrostatic pressure
- Aerodynamic pressure
- Internal circulation
- Electric stress
- If particles cant and orient, the radar-observed
parameters are changed.
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Parameter of Dual-polarization Radar
- Reflectivity Z (Horizontal polarization)
- Doppler velocity v
- Spectrum width s
- Differential reflectivity Zdr
- Cross-correlation coefficient ?hv
- Differential phase fdp
- Specific differential propagation phase Kdp
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Observation with Dual-Pol Radar
- Simultaneous transmission and reception with
horizontal and vertical polarizations - Powers in the horizontal (Ph) and vertical (Pv)
- Differential reflectivity ZDR
- How hydrometeor (rain, hail, graupel, etc.)
shapes in the horizontal and vertical axis
2mm sphere 2mm oblate spheroid
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Observation Parameters
- Copolar cross correlation function Rco
- Cross correlation coefficient ?hv
- (complex conjugate, mtime series)
- If em has large fluctuations, ?hv should be small.
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Observation Parameters
- Differential phase fdp
- Specific differential phase Kdp
- Canting angle and orientation of hydrometeors
- Electrical charged particles
- Kdp should be obtained by fdp as a slope of a
least squares fit
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Parameter of KOUN Radar
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Map of Observation Sites
KOKC Upper-soundings
KTLX
KOUN
Purcell Wind Profiler
Sulphur Upper-soundings
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Animations of KOUN Imageries
- 12-19 UTC on May 27, 2005
- 0.5 deg. Elevation (every 1 min.)
- Reflectivity Zh (filtered many clutters)
- Doppler velocity v
- Differential Reflectivity Zdr
- Kdp
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Example of cold front
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Example of a cold front
May 27, 2005, 1721 UTC Positive away the
radar Negative toward the radar
- A cold front passed over the profiler site
- Strong Zh observed NE and SW of Purcell
- NE parameters except Zh are weak small rains
- SW all parameters are strongLarge rain
particles - Small difference of Doppler velocity across a
front - Large difference perpendicular to the beam
direction
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Summary
- Dual-polarization Doppler radar can obtain
- Distribution of hydrometeors (density, shape,
angle, and type) - Distribution of rain rate and rain amount
- Roughly, movement of precipitating clouds and
clear air disturbances
- Forecasting of thunderstorms, lightning, etc.
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If you want to study more
- Dual-polarization radar and rainfall estimation
- Bringi et al., 2003 JAS, 60, 354-365.
- Ryzhkov et al., 2002 JTECH, 19, 340-354.
- Ryzhkov et al., 2005 JAM, 44, 502-515.
- KOUN radar
- Brown et al., 2005 Wea. Forecast., 20, 3-14.
- JPOLE Web page http//cimms.ou.edu/schuur/jpole/
- Rain shapes
- Beard and Chuang, 1987 JAS, 44, 1509-1524.
- E-mail me! teshiba_at_ou.edu
- See web site http//kyodai.metr.ou.edu/teshiba/
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Large Reflectivity means
- Strong turbulances
- Large slopes of temperature and humidity
- (by the radar equation)
- Large echo is observed along a gust front
But
- The KOUN radar uses the frequency of S-band
- Large reflectivity if there are rain particles in
the radar beam - Observed Doppler velocity should be the sum of
the movement of the air and rain particles
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