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.