Transcript Document 7514477

Performance of water vapor radiometers at 22
and 183 GHz developed at RPG
Thomas Rose, Harald Czekala (Radiometer Physics GmbH)
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
Microwave Bands
Frequencies
:
Humidity Profiling:
22-31.4 GHz Band
(7 channels)
Temp. Profiling
(Trop.): 50-59 GHz
Band
(7
channels)
LWP / IWV / WetDelay:
RPG-TEMPRO
RPG-HATPRO
RPG-HUMPRO
RPG-LWP
90 GHz
23.8
GHz
23.8 / 31.4 GHz
23.8 /31.4 + 90 GHz
36.5/31.4
GHz
RPG-LWP-U90
90 / 150 GHz
183.3 GHz , 4 chan.
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
HATPRO Instrument Configuration
Scanning
paraboloid
mirror
ambient
temperature
target
RPG Radiometer Physics GmbH
beam combiner
(wire grid)
humidity profiler
temperature profiler
WVR Workshop – Wettzell, 9. Oct. 2006
RPG-HATPRO Optical Performance
humidity profiler
23.8 GHz, HPBW = 3.9°, Sidelobes: <-30 dB (6.5)
RPG Radiometer Physics GmbH
temperature
profiler
55.0 GHz, HPBW = 1.9°, Sidelobes: <-30 dB (4.0)
WVR Workshop – Wettzell, 9. Oct. 2006
HATPRO Rain / Dew Protection System
removable
dew blower
Prevent formation of
dew and rain on
microwave window by:
- strong blower system
(150 Watts fan power
1.5 kW heater
module)
- Hydrophobic coating
- Optional heater
module
(1.5 kWatts)
System allows for
humidity profiling
during fog, rain
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
HATPRO Meteorological Station
Weather Station and Time Reference:
Rain Sensor: Provides rain flag for
measurement documentation,
control of super blower system
GPS-Clock: Provides time reference
standard for synchronization
Humidity Sensor: Provides control of
super blower system, documentation
Humidity
Sensor
Temperature Sensor: Documentation
of surface temperature
Temp.
Sensor
Pressure Sensor: Documentation of
baro-metric pressure, LN-target
calibration
Optional
IR-Radiometer: Cloud base
height detection, ceilometer function
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
RPG-HATPRO Receiver Layout
Dual Profiler Direct Detection Filterbank Receivers based on MMIC Technology:
< 600 K System
Noise Temperature
50-60
GHz Band
new Dicke
Switch
design
Direct. Coupler
Det
ISO
LNA
analog
MUX
T0
< 350 K System
Noise Temperature
LNA
WG-Splitter
Noise Injection
Antenna
22-32
GHz Band
BPF
16 Bit
ADC
Pin
Switch
Noise
Diode
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
RPG Waveguide Dicke Switches
WG - Dicke Switch Performance (7.10.2006)
Model
RPG-DS-112
22.4 GHz
WVL
183 GHz
WVL
Band (GHz)
WG
X
6.2 - 10.5
WR-112
Trans. Loss (Off)
I/O-Match
On/Off Isol.
Speed
< 0.2 dB
< --25 dB
> 32 dB
< 20 Hz
RPG-DS-90
Ku
10.5 - 16.0
WR-90
< 0.2 dB
< --23 dB
> 35 dB
< 20 Hz
RPG-DS-42
K
18 - 26.5
WR-42
< 0.25 dB
< --22 dB
> 35 dB
< 20 Hz
RPG-DS-32
K - Ka
20.0 - 33.0
WR-32
< 0.3 dB
< --20 dB
> 35 dB
< 40 Hz
RPG-DS-28
Ka
26.5 - 40.0
WR-28
< 0.3 dB
< --20 dB
> 35 dB
< 40 Hz
RPG-DS-15
V
50.0 - 75.0
WR-15
< 0.35 dB
< --18 dB
> 35 dB
< 40 Hz
RPG-DS-10
W
75.0 - 110.0
WR-10
< 0.4 dB
< --18 dB
> 35 dB
< 40 Hz
RPG-DS-6
D
110.0 - 170.0
WR-6
< 0.5 dB
< --16 dB
> 35 dB
< 40 Hz
RPG-DS-5
G
170.0 - 220.0
WR-5
< 0.6 dB
< --15 dB
> 35 dB
< 40 Hz
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
RPG Waveguide Dicke Switches
90 GHz Direct Detection
Receiver
150 GHz Direct Detection
Receiver
Dicke Switches
Focussing Mirror
Wire Grid
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
RPG-HATPRO Receiver Allan Variance
Receivers obey
radiometer
formula:
T 
Allan Variance (53.86 GHz)
log(time [sec])
0
0.5
1
1.5
2
2.5
3
-0.25
Tsys  Tsig
-0.5
tint  B
or:
log( T )  0.5  log( t int )
Tested up to:
tint = 1000 sec
log(variance)
-0.75
-1
-1.25
-1.5
30 sec. Integr.
Time
→ ∆T = 0.1 K
-1.75
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
Humidity Profiler Calibrations
Automatic Calibrations:
- gain calibration continuously by periodic noise injection
- system noise calibration continuously by Dicke switch
or
ambient target
- tip curve, only for humidity profiler
-Manual Calibrations:
- absolute calibration with liquid nitrogen (calibration of
noise
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
Nonlinearity Calibration
System gain nonlinearity is corrected by 4 point
method:

Detector model:
U D  G(Tsys  Tsig )
Absolute Calibration:
,  1
Ud
Injection of additional
noise TN from precision
noise diode source
U5
4 Equations result in:
U2
U4
U3
U1
G, Tsys, TN, a
Us
Tsys Tc Tn
RPG Radiometer Physics GmbH
Th Tn
Th2
T[K]
WVR Workshop – Wettzell, 9. Oct. 2006
Compact V-Band Receiver Design
55 dB Pre-Amplifier
Splitter and
Filter Section
Boosters and
Detectors
Video Amps,
MUX, 16 Bit ADC
Noise Injection
Coupler
70 mm
200 mm
51-59 GHz 7 Channel
Filterbank Receiver
RPG Radiometer Physics GmbH
Corrugated
Feedhorn
WVR Workshop – Wettzell, 9. Oct. 2006
Compact K-Band Receiver Design
85 mm
280 mm
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
Thermal Receiver Stabilisation
Two stage thermal
stabilisation system:
Receiver stabilisation:
<30 mK over full
operating temperature
range (-30°C to +
45°C)
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
Thermal Receiver Stabilisation
8 hours
0.1 K
+40°C
-30°C
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
How do Retrievals Work?
Radiosonde Data Set
T(h), H(h), e.g. 10000
samples
Profiles T(h), H(h),
derived from
Microwave BTs
RPG Radiometer Physics GmbH
Radiative
Transfer
Calculation
Brightness Temperatures
BT(f), f: water vapour line,
oxygen line
statistical methods:
lin./quadr.regression,
Neural Networks
WVR Workshop – Wettzell, 9. Oct. 2006
IWV Retrievals



18580 high-resolution radio sondes
Rainy conditions included: RMS 0.45 kg/m^2
Clear-sky RMS: 0.2 kg/m^2
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
IWV Comparison with Radiosoundings
HATPRO
RS




140 radio soundings (26. April to 4. July, Cabauw, KNMI)
Radiosonds: Vaisala RS-92
No-Rain RMS: 0.43 kg/m^2, Bias: 0.05 kg/m^2
Two channel RPG-LWP: RMS: 0.6 kg/m^2, Bias similar to HATPRO
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
Example of Rapid WV-Fluctuations
Benin, West Africa, 9. April 2006 (AMMA)
changes of up to 7 kg / m^2 within 1 hour!
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
HATPRO Humidity Profiling up to 10 km
Benin, West Africa, 19. January 2006 (AMMA)
45 kg/m^2
27 kg/m^2
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
Vertical humidity profiles (absolute humidity, 10 km)
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
Vertical profiles (absolute humidity, 10km)
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
HATPRO Humidity Profiling
Comparison with radiosonde data. RMS Error : 1.0 g/m3 on the ground
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
Example: Relative Humidity Profiles without T.-Profile Info
4 days time series (1740 profiles), H < 2000 m
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
Example: Relative Humidity Profiles including T.-Profile Info
4 days time series (1740 profiles), H < 2000 m
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
Example: Relative Humidity Profiles
Temp. Inversion present
no temperature information added
RPG Radiometer Physics GmbH
Temp. Inversion present
temperature information added
WVR Workshop – Wettzell, 9. Oct. 2006
LWP time series
High temp. and spatial res. LWP time series for cloud analysis
temp. res.: 1 sec., abs. acc.: +/-20 g/m2 ,RMS Noise: +/- 2 g/m2
30 g/m2 (=0.03
mm)
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
Instrument Installations
 University of Salford, UK
 ARPAV, Weather Service of Veneto
Italy
 Regione Marche Civil Protection
Centre / Ancona, Italy
 KNMI, Dutch Weather Service,
Cabauw
 Tokyo University / Japan
 University of Munich / Germany,
Zugspitze
 Meteo Swiss / Switzerland, 3 Units
 AMMA Project, West Africa
 Aerospace Corporation / USA
 Institut für Meereskunde in Kiel /
Germany, Research Ship
„Polarstern“
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
183 GHz Water Vapour Radiometer
System Performance:
Frequencies:
183.3 +/- 1.4 GHz, BW: 0.8 GHz
183.3 +/- 3.6 GHz, BW: 1.0 GHz
183.3 +/- 7.0 GHz, BW: 2.0 GHz
183.3 +/- 14.0 GHz, BW: 2.0 GHz
System Noise Temperatures:
Channel 1: 1150 K
Channel 2: 1200 K
Channel 3: 1300 K
Channel 4: 1250 K
Sampling rate: 1 second
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
183 GHz WVR mounted in APEX 12 m Cassegrain
Instrument operated by:
MPI for Radio Astronomy
in Bonn
Site: Atacama desert SA
(ALMA site)
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006
183 GHz WVR Receiver Layout
168-198
GHz
new Dicke
Switch
design
IF-BPF
Noise Injection
Subharmonic
Mixer
Directional
Coupler
Antenna
IF-Amp.
Detector +
DC-Amp
IF-LNA
Splitter
T0
0.5-18 GHz
Isolator
x3
Pin-Switch
Noise Diode
RPG Radiometer Physics GmbH
Local Oscillator
(DRO)
(30.55 GHz)
WVR Workshop – Wettzell, 9. Oct. 2006
Summary of Important Results
• IWV accuracy of 7 channel retrieval including
window channel at 31.4 GHz is in the order of 0.45
kg/m^2 RMS
• 2 channel radiometer (23.8 and 31.4 GHz) provides
slightly less accurate IWV retrieval of 0.6 kg/m^2
RMS
• IWV can be a rapidly changing parameter in
particular close to the sea coast.
• By including a Dicke switch to the receiver input it
is possible to achieve low BT noise of 10 mK (1000
sec. integration time)
RPG Radiometer Physics GmbH
WVR Workshop – Wettzell, 9. Oct. 2006