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LWP Radiometers
(LWP, LWP-U90, LWP-U72+82, LWP-90-150)
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These radiometers are used for the remote sensing of integrated water vapor (IWV) and Liquid Water Path (LWP). Both quantities give column-integrated (total) values rather than vertically resolved profiles.
Applications:
- Liquid water path (LWP) measurements
- Integrated water vapour (IWV) measurements
- Attenuation monitoring
- Beacon experiments
- Cloud observations
- Climate monitoring
- Satellite tracking (GPS, Galileo)
Models:
The RPG-LWP model is the standard two-channel microwave radiometer typically used for this purpose. Upgraded versions (RPG-LWP-U90, RPG-LWP-U150, RPG-LWP-U72+88) extend the sensitivity to small amounts of LWP (e.g., thin clouds) by adding one or two higher frequency channels. High-frequency two channel versions (RPG-LWP-90-150) are optimised for thin cloud and snow observation. For observation of thick clouds and rain we recommend the dual-polarized Rain Radiometer (LWP-Rain).
Model | Frequencies | Applications | Description |
---|---|---|---|
LWP | 23.8 & 31.4 GHz | Standard two-channel radiometer for estimation of IWV and LWP |
The RPG-LWP-XXX series of liquid water path radiometers is meant for measurements of total water vapour (IWV, integrated water vapour) and total cloud water (LWP, liquid water path). Higher sensitivity to low-density (thin) clouds can be achieved by upgrading the standard LWP radiometer with higher frequencies. |
LWP-U90 | 23.8, 31.4, 90 GHz | Improved sensitivity to thin clouds | |
LWP-U150 | 23.8, 31.4, 150 GHz | Improved sensitivity to thin clouds | |
LWP-U72-82 | 23.8, 31.4, 72.5, 82.5 GHz | Improved sensitivity to thin clouds, | |
LWP-90-150 | 90 & 150 GHz | Observation of thin-clouds only. |
Parameter | Specification |
---|---|
IR radiometer option | 9.6-11.5 µm band, accuracy 1 K, noise: 0.2 K RMS |
LWP | Accuracy: ± 20 g/m2,, Noise: 2 g/m2 RMS |
IWV | Accuracy: ± 0.2 kg/m2 RMS, Noise: 0.05 kg/m2 RMS |
Full sky IWV and LWP maps (only with azimuth positioner) | 350 points in 6 minutes rapid scanning |
Satellite tracking mode | Determines wet/dry delay, atmospheric attenuation and humidity profiles along line of sight for all visible GPS / Galileo satellites in a single scan (2 minutes) |
(only with azimuth positioner option) | scanning with RINEX navigation file or direct GPS vector reading from GPS clock |
Channel centre frequencies | 23.8+31.4 (72.5, 82.5, 90, 150 optional) |
Channel bandwidth | 2 GHz @ 72 to 150 GHz, 230 MHz @ all other |
System noise temperatures | < 400 K typical, < 600 at 70 to 90 GHz typical |
Radiometric resolution | 0.1 RMS typical @ 1.0 sec integration time |
Absolute brightness temperature accuracy | 0.5 K |
Radiometric range | 0-800 K |
Absolute calibration | with internal ambient & external cold load |
Internal calibration | gain: with internal noise standard |
gain + system noise: ambient temp. target + noise | |
abs. cal. of humidity profiler: sky tipping calibration | |
Receiver and antenna thermal stabilization | Stability better than 0.03 K over full operating temperature range |
Gain nonlinearity error correction | Automatic, four point method |
Brightness calculation | based on exact Planck radiation law |
Integration time | ≥ 0.4 seconds for each channel, user selectable |
Sampling rate for profiles | ≥ 1 sec, user-selectable |
Rain / fog mitigation system | Highly efficient blower system (130 Watts), hydrophobic coated microwave transparent window, 1.8 kW heater module preventing formation of dew under fog conditions |
Environmental Sensors | On a 1-meter mast attached to the radiometer: |
Temperature, pressure, relative humidity | |
Wind speed, wind direction | |
Data interface / rate | Ethernet (TCP/IP) |
Instrument control (external PC) | Windows™ System with Ethernet interface |
Instrument control (internal) | Embedded PC, controls all internal calibrations, data acquisition, data file backup on 1 GB flash memory, control of azimuth positioner, communication with host, can run measurements independently from host PC |
Housekeeping | all system parameters, calibration history documentation |
Retrieval algorithms | neural network, linear /nonlinear regression algorithms |
Optical resolution | HPBW: ≤ 4° (≤ 2° at 72 GHz and above) |
Side-lobe level | <-30dBc |
Pointing range / resolution | Elevation: 0° to 180° (0.15° steps), full s/w control |
Azimuth (optional): 0° to 360° (0.1° steps), full s/w control | |
Pointing speed | 45°/sec (elevation), 40°/sec (azimuth, optional) |
Operating temperature range | -40°C to +45°C |
Power consumption | <120 Watts average, 350 Watts peak for warming-up (without dew blower heater), blower: 130 Watts max. |
Lightning protection | Power line: circuit breakers |
Data line: Fibre optics cable (max. length: 1400 m) | |
Input voltage | 90-230 V AC, 50 to 60 Hz |
Weight | 60 kg (without dew blower) |
Dimensions | 63 × 36 × 90cm3 |
Extendibility (master-slave mode) | Any single-polarization std. radiometer |
Customization | Frequencies and bandwidth adaptable |
Weather station | Lufft WS600-UMB |
Center frequencies and channel bandwidth may be customized without a major effort. Any combination of two waveguide-bands in one instrument is possible.
- Network capability through Ethernet Interface
- High spatial resolution due to small beam widths (<4° HPBW, frequency dependent)
- High temporal resolution: filter bank receiver produces one observation per second
- Absolute system stability: 0.5 K
- Receiver and antenna thermal stabilization: < 0.02 K
- Operating temperature range: –40°C to +45°C
- Automatic rain-mitigation system: hydrophobic coating and strong blower for rain, heater module with 1.8 kW preventing formation of dew and fog condensation on radome.
- Integrated PC on-board
- Comprehensive operating software included (free updates)
- Full internal retrieval algorithm, retrieval data and raw data output
- GPS clock and receiver
- Additional external meteorological sensors: barometric pressure, humidity, temperature, wind (direction and speed), rain rate
- IR-radiometer option for ice cloud detection
- Azimuth positioner option for full sky scanning: 350 observations of IWV, LWP, IR temperature in less than 6 minutes
- North-alignment by software feature (sun-tracking plus GPS, only with azimith positioner)
- Fiber-optical data cable for lightning protection and secure data transmission (maximum length 1600 m)
- Customized retrieval software available
- Stand alone operation
- Data storage and backup on-board, power-failure safe-guard
- Low maintenance (6 months intervall for absolute calibration using LN2)
- Automatic calibration with sky-tipping (software controlled)
- Power supply: 100 – 240 V AC (at 47 – 63 Hz)
- Power consumption: <120 W average, 350 W peak during warm-up, blower 130 W maximum.
- Weight: 60 kg (without dew blower)
- Dimensions: 63 × 40 × 90 cm (H × W × L, without stand)
- Low cost!
Options:
channels at 23.8, 31.4, 72.5, 82.5, 90, 150, 225, 350, 448, 664 GHz
Retrieved data types:
- Liquid Water path (LWP)
- Integrated Water Vapor (IWV)
- wet delay
- dry delay
Aussaguel, France
RPG-, LWP Radiometer third generation liquid water path radiometer
- Deployment since 2011
- Atmospheric attenuation measurements, telecommunications
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Rome, New York, USA
2 x RPG-LWP-U72-82 liquid water path radiometers
- Deployed in 2010 and 2012
- Atmospheric attenuation measurements, telecommunications
ARM Mobile Facility, COPS Campaign, Germany
University of Bonn, Germany
RPG-150-90 liquid water path radiometer
- Deployment period: June-December 2007
- Later deployments: Barrow, Alaska
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RPG_MWR_LWP_TN_2016.pdf
RPG_MWR_STD_Installation_Manual_2015.pdf
RPG_MWR_STD_Software_Manual 2015.pdf
RPG_MWR_STD_Technical_Manual_2015.pdf
RPG_MWR_STD_Measurements-Deployment_Manual_2015.pdf