rpg radiometer physics gmbh wvr workshop – wettzell, 9. oct. 2006 performance of water vapor...

RPG Radiometer Physics GmbH WVR Workshop – Wettzell, 9. Oct. 2006

Performance of water vapor radiometers at 22 Performance of water vapor radiometers at 22 and 183 GHz developed at RPGand 183 GHz developed at RPG

Thomas Rose, Harald Czekala (Thomas Rose, Harald Czekala (Radiometer Physics GmbH)Radiometer Physics GmbH)


Microwave BandsMicrowave BandsFrequencies:

Humidity Profiling: 22-31.4 GHz Band (7 channels)

LWP / IWV / Wet-Delay:

23.8 / 31.4 GHz

23.8 /31.4 + 90 GHz

90 / 150 GHz

183.3 GHz , 4 chan.

Temp. Profiling (Trop.): 50-59 GHz Band (7 channels)

RPG-LWP

RPG-HATPRO

23.8 GHz

36.5/31.4 GHz

90 GHz

RPG-HUMPRO

RPG-TEMPRO

RPG-LWP-U90


HATPRO Instrument ConfigurationHATPRO Instrument Configuration

Scanningparaboloidmirror

ambienttemperaturetarget

beam combiner(wire grid) humidity profiler

temperature profiler


RPG-HATPRO Optical PerformanceRPG-HATPRO Optical Performance

23.8 GHz, HPBW = 3.9°, Sidelobes: <-30 dB 55.0 GHz, HPBW = 1.9°, Sidelobes: <-30 dB(6.5) (4.0)

humidity profiler temperature profiler


HATPRO Rain / Dew Protection SystemHATPRO Rain / Dew Protection System

removabledew 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


HATPRO Meteorological StationHATPRO 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 synchronizationHumidity Sensor: Provides control of super blower system, documentationTemperature Sensor: Documentation of surface temperaturePressure Sensor: Documentation of baro-metric pressure, LN-target calibration

Humidity Sensor

Temp. Sensor Optional IR-Radiometer: Cloud base

height detection, ceilometer function


RPG-HATPRO Receiver LayoutRPG-HATPRO Receiver LayoutDual Profiler Direct Detection Filterbank Receivers based on MMIC Technology:

Antenna

Direct. Coupler

Pin Switch

Noise Diode

Noise Injection

LNA

WG-Splitter

DetBPF

T 0

ISO

LNA

50-60 GHz Band

22-32 GHz Band

new Dicke Switch design

analogMUX

16 BitADC

< 600 K System Noise Temperature

< 350 K System Noise Temperature


WG - Dicke Switch Performance (7.10.2006)Model Band (GHz) WG Trans. Loss (Off) I/O-Match On/Off Isol.

RPG-DS-112 X6.2 - 10.5 WR-112 < 0.2 dB < --25 dB > 32 dB

> 35 dB< --23 dB< 0.2 dBWR-90RPG-DS-90 K u10.5 - 16.0

RPG-DS-42 K18 - 26.5 WR-42 < 0.25 dB < --22 dB > 35 dB

RPG-DS-32 K - K a20.0 - 33.0 WR-32 < 0.3 dB < --20 dB > 35 dB

Speed

< 20 Hz

< 20 Hz

< 20 Hz

< 40 Hz

RPG-DS-28 K a26.5 - 40.0 WR-28 < 0.3 dB < --20 dB > 35 dB < 40 Hz

RPG-DS-15 V50.0 - 75.0 WR-15 < 0.35 dB < --18 dB > 35 dB < 40 Hz

RPG-DS-10 W75.0 - 110.0 WR-10 < 0.4 dB < --18 dB > 35 dB < 40 Hz

RPG-DS-6 D110.0 - 170.0 WR-6 < 0.5 dB < --16 dB > 35 dB < 40 Hz

RPG-DS-5 G170.0 - 220.0 WR-5 < 0.6 dB < --15 dB > 35 dB < 40 Hz

22.4 GHz WVL

183 GHz WVL

RPG Waveguide Dicke SwitchesRPG Waveguide Dicke Switches


RPG Waveguide Dicke SwitchesRPG Waveguide Dicke Switches

150 GHz Direct Detection Receiver

Wire Grid

Focussing Mirror

90 GHz Direct Detection Receiver

Dicke Switches


RPG-HATPRO Receiver Allan VarianceRPG-HATPRO Receiver Allan Variance

Allan Variance (53.86 GHz)

-1.75

-1.5

-1.25

-1

-0.75

-0.5

-0.25

0 0.5 1 1.5 2 2.5 3

log(time [sec])

log

(va

ria

nc

e)

Receivers obeyradiometer formula:

Bt

TTT sigsys

int

or:

)log(5.0)log( inttT Tested up to:tint = 1000 sec

30 sec. Integr. Time→ ∆T = 0.1 K


Humidity Profiler Calibrations 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

standards)


Nonlinearity CalibrationNonlinearity Calibration

System gain nonlinearity is corrected by 4 point method:

Ud

T[K]Tn TnTsys Tc Th Th2

U1

U2

U3

U4

U5

Us

Detector model: 1,)( sigsysD TTGU

4 Equations result in:

G, Tsys, TN, a

Absolute Calibration:

Injection of additional noise TN from precision noise diode source


Compact V-Band Receiver DesignCompact V-Band Receiver Design

Splitter and Filter Section

Boosters and Detectors

Video Amps,MUX, 16 Bit ADC

55 dB Pre-Amplifier

Noise InjectionCoupler

51-59 GHz 7 ChannelFilterbank Receiver

Corrugated Feedhorn

200 mm

70 mm


Compact K-Band Receiver DesignCompact K-Band Receiver Design

280 mm85 mm


Thermal Receiver StabilisationThermal Receiver Stabilisation

Two stage thermal stabilisation system:

Receiver stabilisation:

<30 mK over full opera-ting temperature range (-30°C to + 45°C)


Thermal Receiver StabilisationThermal Receiver Stabilisation

0.1 K

-30°C

+40°C

8 hours


How do Retrievals Work?How do Retrievals Work?

Radiosonde Data SetT(h), H(h), e.g. 10000samples

Brightness TemperaturesBT(f), f: water vapour line,oxygen line

Radiative

TransferCalculation

statistical methods:lin./quadr.regression,Neural Networks

Profiles T(h), H(h), derived from Microwave BTs


18580 high-resolution radio sondes18580 high-resolution radio sondes Rainy conditions included: RMS 0.45 kg/m^2Rainy conditions included: RMS 0.45 kg/m^2 Clear-sky RMS: 0.2 kg/m^2Clear-sky RMS: 0.2 kg/m^2

IWV RetrievalsIWV Retrievals


IWV Comparison with RadiosoundingsIWV Comparison with Radiosoundings

140 radio soundings (26. April to 4. July, Cabauw, KNMI)140 radio soundings (26. April to 4. July, Cabauw, KNMI) Radiosonds: Vaisala RS-92Radiosonds: Vaisala RS-92 No-Rain RMS: 0.43 kg/m^2, Bias: 0.05 kg/m^2No-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 HATPROTwo channel RPG-LWP: RMS: 0.6 kg/m^2, Bias similar to HATPRO

HATPRORS


Example of Rapid WV-FluctuationsExample of Rapid WV-Fluctuations

changes of up to 7 kg / m^2 within 1 hour!changes of up to 7 kg / m^2 within 1 hour!

Benin, West Africa, 9. April 2006 (AMMA)


HATPRO Humidity Profiling up to 10 kmHATPRO Humidity Profiling up to 10 km

Benin, West Africa, 19. January 2006 (AMMA)

45 kg/m^2

27 kg/m^2


Vertical humidity profiles (absolute humidity, 10 km)Vertical humidity profiles (absolute humidity, 10 km)


Vertical profiles (absolute humidity, 10km)Vertical profiles (absolute humidity, 10km)


HATPRO Humidity ProfilingHATPRO Humidity Profiling

Comparison with radiosonde data. RMS Error : 1.0 g/m3 on the ground


Example: Relative Humidity Profiles without T.-Profile InfoExample: Relative Humidity Profiles without T.-Profile Info

4 days time series (1740 profiles), H < 2000 m4 days time series (1740 profiles), H < 2000 m


Example: Relative Humidity Profiles including T.-Profile InfoExample: Relative Humidity Profiles including T.-Profile Info

4 days time series (1740 profiles), H < 2000 m4 days time series (1740 profiles), H < 2000 m


Example: Relative Humidity ProfilesExample: Relative Humidity Profiles

no temperature information addedno temperature information added

Temp. Inversion present

temperature information addedtemperature information added

Temp. Inversion present


LWP time seriesLWP 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)


Instrument InstallationsInstrument 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“


183 GHz Water Vapour Radiometer183 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


183 GHz WVR mounted in APEX 12 m Cassegrain183 GHz WVR mounted in APEX 12 m Cassegrain

Instrument operated by:

MPI for Radio Astronomy in Bonn

Site: Atacama desert SA (ALMA site)


183 GHz WVR Receiver Layout183 GHz WVR Receiver Layout

Antenna

Directional Coupler

Pin-Switch

Noise Diode

Noise Injection

Splitter

SubharmonicMixer IF-LNA

Local Oscillator (DRO) (30.55 GHz)

Detector + DC-AmpIF-Amp.IF-BPF

168-198 GHz

0.5-18 GHz

x3

IsolatorT 0

new Dicke Switch design


Summary of Important ResultsSummary of Important Results

• IWV accuracy of 7 channel retrieval including IWV accuracy of 7 channel retrieval including window channel at 31.4 GHz is in the order of window channel at 31.4 GHz is in the order of 0.45 kg/m^2 RMS0.45 kg/m^2 RMS

• IWV can be a rapidly changing parameter in IWV can be a rapidly changing parameter in particular close to the sea coast.particular close to the sea coast.

• 2 channel radiometer (23.8 and 31.4 GHz) 2 channel radiometer (23.8 and 31.4 GHz) provides slightly less accurate IWV retrieval of provides slightly less accurate IWV retrieval of 0.6 kg/m^2 RMS0.6 kg/m^2 RMS

• By including a Dicke switch to the receiver input By including a Dicke switch to the receiver input it is possible to achieve low BT noise of 10 mK it is possible to achieve low BT noise of 10 mK (1000 sec. integration time)(1000 sec. integration time)

rpg radiometer physics gmbh wvr workshop – wettzell, 9. oct. 2006 performance of water vapor...

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