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Advances in Science and Techniques for Ground-Based Radar Remote-Sensing of the
Earth’s Atmosphere
Shoichiro Fukao Fukui University of Technology, Fukui
Research Institute for Sustainable Humanosphere, Kyoto University, Kyoto
IGARSS
Vancouver, Canada July 24 -29, 2011
Structure of the Earth’s Atmosphere
Troposphere
Mesosphere and Stratosphere
Thermosphere/ Ionosphere
The Principle of radar techniques
Transmitter
Receiver
Antenna
Pulse
Echo
Target
Frequency
Doppler shift
Frequency
The latest radar techniques have continuously been applied to the Earth’s atmosphere
Lower Atmosphere
Middle Atmosphere
Upper Atmosphere
First, meteorologists utilized radars for precipitation measurement.
The latest radar techniques have continuously been applied to the Earth’s atmosphere
Lower Atmosphere
Middle Atmosphere
Upper Atmosphere Next, radar techniques were utilized by upper atmosphere physicists.
Scatterer in the ionosphere: Free Electrons
Total cross section is comparable to that of a sphere of 1 cmφ.
Incoherent scattering or IS
The latest radar techniques have continuously been applied to the Earth’s atmosphere.
Lower Atmosphere
Middle Atmosphere
Upper Atmosphere
Finally, radar techniques were applied to the middle atmosphere.
Scatterer in the Middle Atmosphere: Turbulence
Bragg scattering
Eddy size responsible for the scattering = One half the radar wavelength
Scales of eddies of (Inertial subrange) turbulence
Troposphere
Stratosphere
Mesosphere
Ionosphere/ Thermosphere
Restricting the radar wavelength for middle atmospheric observations to VHF and UHF.
Rapid beam scanning required for accurate measurement of wind velocity
Radar antenna
Wind vector measurement: Wind velocity assumed to be uniform within
the region where / the duration while the beam is steered.
The Middle and Upper Atmosphere radar : The MU radar
Two essential capabilities: - Beam steering on a pulse-to-pulse basis, and - Multiple beam forming
● Several hundred modules of transmitters/ receivers. ● Computer control of the whole system
ACTIVE PHASED ARRAY RADAR
MU
The MU radar, Shigaraki, Japan
Research Institute for Sustainable Humanosphere, Kyoto University
46.5 MHz, 103mφ Yagi array, 1 MW
The MU radar features an active phased array:
Mete
oro
logi
cal
bal
loon o
bserv
atio
n
6 hrs interval
Atmospheric radars provide continuous wind data with high time and altitude resolutions that have ever been realized.
MUレーダー観測
Passage of a typhoon Mete
oro
logi
cal
bal
loon o
bserv
atio
n A
tmosph
eric
radar obse
rvation
Atmospheric radars provide continuous wind data with high time and altitude resolutions that have ever been realized.
Daily mean (a) eastward (solid) and northward (dashed) radial velocity profiles and hourly mean radial velocity fluctuations in the (b) east and (c) north directions for 17/18 October (after Fritts et al., 1988).
Mean wind (20 oblique) Fluctuations from the mean wind
Vr (Meridional)
Atmospheric waves modulate tropo/stratospheric wind profiles.
Meridional Zonal
Ur (Zonal)
°
Atmospheric waves modulate mesospheric wind profiles more extensively
Zonal wind
Heig
ht
北斎
Analogy to ocean surface waves: Their growth and breaking
Woodcut print painted by Hokusai Katsushika (19th century)
Atmospheric gravity waves: Propagation and saturation
Deceleration of mean flow
Atmospheric gravity waves
Saturation
Momentum flux
Wave breaking
Turbulence
Weak wind
Latitudinal distribution of zonal wind velocity in the mesosphere
Theoretically, a strong geostrophic wind exists above the mesosphere.
Observationally, the wind is weak irrespective of season and latitude.
E: Easterly or westward wind W: Westerly or eastward wind
Momentum flux measured with the MU radar
Eastward flux
Westward flux
Deceleration of westward wind Deceleration of
eastward wind Mean flow westward
Mean flow eastward
(Model vs Observational results)
Saturation of atmospheric gravity waves
k :
k-3
k-3
k :
Gravity waves found to be ubiquitous in the ionosphere and thermosphere
“Gravity waves” continuously modulate the structure and dynamics of this region.
Dispersion relation for thermospheric gravity waves
Sata
Darwin
Darwin
Sata
Darwin
EAR
Projected along geomagnetic
field line
Hemispheric conjugacy of nighttime MSTIDs
Otsuka et al., 2004
630-nm airglow imagers simultaneously taken at conjugate points.
z †FY (t) (t)h (z)Y=
X
X
X
h1(z)
h2(z)
h3(z)
Σ
Y1(t)
X
h4(z)
X
h5(z)
Reconstructed time series at z within range volume
zFY (t) =
Y2(t)
Y3(t)
Y4(t)
Y5(t)
The principle of range imaging
適用する空間フィルター: T1 2 N 1 N(z) [h (z) h (z) h (z) h (z)]h −= L r /2 z r /2−Δ < <Δ r 150mΔ =
2 *F FP (z) E{Y (t) } h Rh= =
:(N×N)エルミート行列 )()( * tYtY=R
(輝度分布~強度に比例) 時系列 (I&Q)
)(1 tY
)(2 tY
)(3 tY
)(4 tY
)(5 tY
T1 2 N 1 NY(t) [Y (t) Y (t) Y (t) Y (t)]−= L
kY (t) :周波数 k の複素受信信号列 ,
Doppler spectrum
レンジ内の任意高度 z における -noise, -power, -SNR, -Doppler velocity, -spectral width
(Range imaging mode)
MUR in range imaging mode
⇒ Detailed observation of turbulence and stable layers at a time and range resolution comparable to standard weather radars.
Simultaneous measurements with cloud radars
Ka-band (35 GHZ) and W-band (95 GHz) Doppler radars
For profiling cloud structures and processes as well as motions from Doppler shift.
Cirrus detected with a Ka-‐‑band radar at shigaraki
94.79GHz FMCW Falcon radar Ref: hLp://katla.nd.chiba-‐‑u.jp/intro/fmcw.html
MUR reflectivity
MUR vertical air velocity
3. A better knowledge of turbulence in clouds and at cloud edges (mechanisms, occurrence, intensity) and mainly cirrus Tools: lidar, weather radars, MU radar, IWP, balloon
KH Instability at a cirrus cloud base observed by MUR
KH instability inside cloud observed from lidar Convective instability at a cloud base (solid line)
observed by MUR
Turbulence in clouds
WINDAS : Wind profiler network and data acquisition system - Japan Meteorological Agency (JMA) 2001 -
・Consists of thirty-one 1.3GHz profilers (LTR) and control center, and ・Provides the NWPs with initial values of wind field.
0 500km
WIND PROFILER SITES
CONTROL CENTER (JMA HQ)
RADIOSONDE STATIONS
LTR, RISH Kyoto Univ.
Impact of profiler data to MSM for severe rainfall
(c) Composite of radars and rain gauges
(a) 3hr forecast of MSM without profiler data
(b) 3hr forecast of MSM including profiler data
Total Rain Amount for 3hr (mm)
Profiler
200km Rawinsonde
Operational Wind Profiler Networks
from www.ecmwf.int
NOAA Profiler Network
WINPROF (CWINDE)
Japan Met Agency
Atmospheric temperature measurement with RASS: Radio Acoustic Sounding System
Horn speaker system
RASS profile
Atmospheric temperature profiles with the MU radar - RASS
- Profiles are successively obtained every three minutes.
RASS contour
Temperature fluctuation and wind vectors near cold front surface
Cold Front Surface
Equatorial Atmosphere Radar: EAR
Antenna array (110 m in diameter)
47MHz, 560 Yagi antennas, 100kW
Bukittinggi, West Sumatra, Indonesia
(0.20 S, 100.32 E,
865 m above sea level)
° °
The Equatorial Atmosphere Observatory (EAO) Kototabang, Indonesia
µ-rain radar
Ceilometer
Disdrometer
Optical rain gauge
Radiometer
RASS sounder
X-band met radar
GPS receiver
All sky imager
VHF radar
Lidar
EAR receiver
EAR
FMCW radar Meteor radar
×:cold-point tropopause
Breaking Kelvin wave
Increase of turbulence
Zonal wind
Turbulence
Large-scale convective system of ISV
成層圏と対流圏の 大気の交換
EAR: Breaking of Kelvin wave at the tropopause
wave
wave excitation
Fujiwara et al., 2003
Where will the “gene” of active-phased array radars go?
MAARSY, Andoya
Equatorial Atmosphere Radar
MU radar
PANSY radar
An MUR-type radar being build at
Syowa base in the Antarctic
MAARSY
Concluding Remarks - In the last forty years, atmospheric radars have been proving themselves a most powerful tool for revealing the basic processes of the Earth’s atmosphere. - Currently, various new sophisticated techniques are being developed with atmospheric radars, and their commercial models are successfully implemented to operational weather forecast. - In the future, they will make most important contributions to studies of the atmospheric sciences, e.g., the climate change.
Thank you for your attention.