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Model: MRR-2, FM-CW MODE
Price: From £POA
Delivery: 6 - 8 WEEKS ARO


A vertical pointing microwave profiler for the measurement of rain rate, liquid water content and drop size distribution from near ground to several hundred metres.
Applications include now-casting of precipitation events, weather radar signal adjustment, hydrology / precipitation studies and cloud physics studies

Research projects using the Micro Rain Radar                                Where to buy Metek instruments

Micro Rain Radar for precipitation profiling

Comprehensive illustration facilities are included with the graphic software


Contour plot of rain         Statistical rain rate analysis       Time series of liquid water
content for different heights

 (click to expand images)

The Micro Rain Radar (MRR) is a vertical pointing microwave profiler for the measurement of rain rate, liquid water content and drop size distribution from near ground to several hundred metres.

Applications include:
  • Observation of the melting layer (bright band / freezing layer)..... read more (new window)
  • Dropsize distribution ... read more (new window)
  • Now-casting of precipitation events ... read more (new window)
  • Weather radar signal adjustment
  • Hydrology / precipitation studies
  • Cloud physics studies
  • Rain measurements on ships and platforms
  • Chemistry changes through precipitation transport

The unique and innovative Micro Rain Radar (MRR) is a small, portable and easy to operate. It can be used for now-casting of precipitation ie, it will detect the start of rain from ground level to high above the radar several minutes before the start of rain at ground level.

It is a highly reliable system suitable for use in remote and extreme environments, requiring minimal maintenance and is well adapted for long term unattended operation.

Statistically stable drop size distributions can be derived within a few seconds due to the size of the scattering volume. The Micro Rain Radar (MRR) can detect very small amounts of precipitation (below the threshold of conventional rain gauges) detecting drop sizes between 0.25 mm and 4.53 mm. This covers the size range of atmospheric occurring precipitation drops as larger drops in the atmosphere are affected by the air resistance as they fall and will split into smaller drops.

The droplet number concentration in each drop-diameter bin is derived from the backscatter intensity in each corresponding frequency bin. In this procedure the relation between terminal falling velocity and drop size is exploited.

The data is available in raw data format, last data set, averaged data set and other modes. The accompanying software package allows you to control the settings, visualise the data, print it and export it to other applications for viewing, publication and storage etc.


  • vertical profiles of rain rate and liquid water content up to 6 km (3.7 miles)
  • computes detailed drop size and distribution output
  • user adjustable averaging intervals and height resolution
  • very low maintenance
  • high system reliability
  • remote/ long term unattended operation
  • high quality measurements
  • no wind, sea spray or evaporation induced errors
  • adjustable averaging intervals 10 - 1800 s
  • height range steps between 35 m to 200 m (600 ft) with 30 range gates
  • battery or mains power

General System Description

The Micro Rain Radar (MRR) system consists of a antenna dish, radar transmitter and receiver unit and RS-232 or RS422 data transmission interface.

The offset parabolic dish antenna is the largest component of the unit and is the same size as a typical home satellite dish (60 cm) with a beam width of 2 °, 6 dB. The radar front end (electromagnetic feed), Ø 8 cm x 10 cm is connected to the transmitter control electronic housing.

The transmitter control box is 26 cm x 16 cm x 10 cm (IP65) and houses the entire transmitter and receiver electronics and does some very basic processing on the received data.  (Receiver unit and digital signal processor unit for FFT (Fast Fourier Transform) - analysis for derivation of Doppler spectra with a 10 s sampling time).

The processed signal is passed through the power and data cable which can be up to 25 m away allowing the radar to be positioned a short distance from where the data will be collected, processed and visualised.

Component parts of the Micro Rain Radar     Dimensions of the Micro Rain Radar  Please click images to expand

Shipping Dimensions

The overall dimensions of the assembled MRR are approximately 60 cm x 60 cm x 60 cm, weight 12 kg

For shipping we use the following packages:
1 wooden crate, 85 x 75 x 30 cm, approx. 30 kg
1 cardboard box, 80 x 80 x 40 cm, approx. 18 kg

How it works

The MRR radar dish acts as both transmitter and receiver using a Frequency Modulated Continuous Wave (FMCW) signal to transmit and receive continuously into the atmosphere. The MRR measures a sample volume above the unit in an expanding cone as it goes up in the atmosphere and due to the continuous transmission of the device it can determine a great deal of statistical information on the drop size distribution from the precipitation that is falling through the sample volume using some very intelligent processing. The measurements are not affected by wind which can be a major factor for many optical or catchment devices and allows the MRR to produce much more accurate drop size distributions than were previously possible.

Live Data Example

A mobile Micro Rain Radar known as the M2R2 has been deployed as part of a network of MRRs in North Carolina to help with ice storm prediction.

For live and raw data from this network see


Micro Rain Radar Specifications

Transmit power 50 mW
Frequency 24.1 to 24.15 GHz
Sampling time 10 s *
Averaging interval - adjustable 10 - 3600 s
Height resolution (steps) - adjustable 10 - 200 m
Lowest usable measuring height: 2 height steps
Number of height steps (range gates) - adjustable up to 30
Accuracy for 1 min average 1/100 mm/h
Modulation type:   saw tooth

depends on adjusted height resolution ie:
1.5 MHz for 100 m height steps
3 MHz for 50 m height steps
Power supply both mains driven (100 - 240 VAC)  or 24 VDC available as standard
Power consumption 25 W @ 24 VDC
Radiated Power 50 mW

10  kg

(without power supply and cable)

Software for online control, data visualisation, transfer and storage MRR control software + MRR graphics program
Cable - data and power 25 m
Data transmission interface RS232 or RS422
Automatic restart after power breakdown with no loss of settings Yes

* for the data transmission of the Doppler spectra from the outdoor receiver and FFT-electronic to the indoor data acquisition PC a transfer time of 2-3 s is required. Therefore, for a 10 s sampling time only 7-8 s are used for effective measurements.


Optional items for the Micro Rain Radar (MRR) include:

  • heating for the parabolic antenna dish
  • a device server for connecting the MRR over Ethernet instead of the standard serial port

Heating of the parabolic antenna dish

The optional heating provides strong heating of the antenna dish to ensure error free operation during snow and icing conditions.

The heating is only required when there is a risk of falling snow accumulating on the dish which could cause issues with the focusing of the transmitted and received signals.

The heating includes a heater element covered by a protective shield with 500 Watt heating power, a 25 m cable and the non-removable heating elements which are located on the reverse side of the antenna. There is also a regulating thermostat dial in a weatherproof housing on the reverse side of the dish which is user adjustable.

Optional device server to convert the signal from RS232 to 10/100 Mbps

The basic MRR unit data output is RS232 serial data. With the device server it is possible to connect the MRR data output to existing local Ethernet networks via the network port of the data acquisition system (see recommended PC specifications on the MRR details page). This permits data transfer across a local network as well as remote maintenance capability.

Please note that a RS232 to USB adapter often cannot provide sufficient performance for the data conversion for several reasons and therefore we can only recommend the conversion to Ethernet protocol.

The Ethernet converter specifications are:

  • Connector type: 9 way D type (female) to RJ45
  • Protocols: TCP/IP, UDP, Telnet, DHCP, ICMP, HTTP, SNMP, DNS
  • Power: 9 to 30 VDC, 200mA @ 12V (internal) / External: 100 - 240 VAC
  • Dimensions: 73 x 121 x 27 mm, the housing is not suitable for use outdoors therefore must be located indoors or in an appropriate enclosure.
  • Operating Temperature: 0°C to 60°C
  • Weight: 0,2 kg

The Optional data conversion device is only required if you want to convert the output from RS232 to Ethernet but do not have a serial 9 way DB-9 port available on your PC or notebook.

It is important to note that the MRR cannot be used with notebooks or PC's using NON native serial ports (such as PCMIA or USB converters) as these have been tried but proven to be unreliable or have slight timing issues over time with the MRR communications.


There are two software components supplied with the MRR, the first is the controlling software to set the parameters of the MRR and the second is software to view the Doppler spectra and visualise the data graphically for presentation etc.

The controlling software is quite simple to use and allows the user to specify the parameters that should be measured or calculated from the raw data as well as to specify whether the PC should save data all of the time or only when it is raining. This software is called MRR control.

The data output by the MRR is ASCII human readable data (ASCII data in serial format). It can be saved as ‘raw data’ for later reprocessing as well as processed data with and without averaging (for more information on file sizes and processing data please read saving data). The data files can either be visualised using a third party program of the user's choice or with the software package that is included with the MRR. Using the MRR visualisation software the data can be viewed from 1 hour periods to 1 month periods or more. The software allows the user to set colour schemes, view several different types of data plots including drop size distributions, reflectivity, times series accumulations among others. This supplied graphics tool is call Metek Graphics software.

Both the control and graphical sets of software are included with the basic MRR unit price and you can have as many copies of the software running as you wish on a network. Several versions of the MRR graphic user interface can be run on a single PC providing there is enough processing power available.

Control Software

The system provides:
  • profiles of droplet spectra (i.e. drop size distribution)
  • radar reflectivity
  • liquid water content and rain rate (with regards to Mie-scattering)
  • signal attenuation and density dependant fall velocity
Output of measured data (spectra, reflectivity, rain rate, liquid water content) both as instantaneous and averaged data (with selected averaging interval)


The system provides:
  • Software module for on-line evaluation of Doppler spectra (measured data see above)
  • Software module for graphic presentation of results and data with:
  • profiles, time series, droplet spectra, statistics or 4- or 9- plot display in a single graphic window
  • selectable time and height ranges
  • smoothing functions
  • printer output
  • export capability to *tif, *eps, *wmf, bmp, txt, etc.


The MRR unit requires a computer with MS Windows software for the data acquisition and the derivation of the precipitation parameters.

We can supply the system with an optional PC or Notebook if required, in which case we will install the software, carry out a system calibration and configuration as well as a test of components at Biral for complete functionality. If the MRR is supplied without a computer you will need to be responsible for this work and compatibility.

Recommended minimum specifications:
  • WINDOWS 2000 or XP
  • 600 MHz (1.2 GHz for full operation of the graphical visualisation software)
  • Pentium III
  • 512 MB
  • 15’’ VGA Monitor
  • 20.0 GB HD
  • CD-Writer (or DVD writer)
  • 1 serial port native 9-way D-type
  • Ethernet port

The serial port must be native and not provided over a PC card or USB to serial adapter, as these tend to be unreliable or cause conflicts due to the very large amount of data every 10 seconds.

Please note that if we do not supply the PC or Notebook as an option we cannot guarantee that the MRR and computer will work together flawlessly. This caveat is only there because we cannot guarantee that ANY brand of PC and MS Windows installation will be working well before the MRR software is installed. Biral will of course work together with any user to try to resolve any issues with software or hardware should this be a problem.


Base for installing the Micro Rain Radar on the groundThe Micro Rain Radar (MRR) is delivered with either a cylindrical base for ground mounting (pictured left) or an adjustable adapter for mounting on a mast or post in a field or on a building or other appropriate structure. The adapter is suitable for fixing to a cylindrical mast with a maximum outer diameter of 48 mm - (common to scaffolding tubing). Note a mast is not included in the delivery.

The MRR must be installed with an absolutely vertical orientation with a maximum of one degree of error tolerance for best accuracy.

For mast mounted installations the MRR should be secured to a mast or structure so that it will not move (in comparison to the mast). Ideally the mast should not be more than 2 m in height to minimise any vibration and if fixed to a longer mast we would recommend securing the mast section at a point so that the unsecured section is less than 2 m (by using guy ropes or other means to immobilise the mast). The affect of vibration on a secure mast up to 2 m high is negligible and will not affect data quality.

Support and Spare Parts

The Micro Rain Radar is of a high quality and built to have an extremely long life with little to no maintenance.

Biral and Metek (the manufacturer of the MRR) have a policy to maintain a stock of replaceable items for 5 years from the date that manufacture ceases and there are no plans to cease manufacture in the foreseeable future.

Biral offer free support by telephone, email or fax for the lifetime of our sensors.


The Micro Rain Radar comes with 1 year parts and labour warranty as standard. For extended warranty please contact Biral for a quotation.

Frequency permission and operation of the MRR

The customer / end user is liable for the acquisition of the frequency permission and the operation of the MRR system for the region of use. Biral can provide guidance to users in acquiring permission.


Various training packages are available to suit your requirements. Please contact Biral for further details.

Contact Biral for more information

To find out more about this instrument or to discuss your application requirements please do not hesitate to contact Biral.

  • telephone to 01275 847787 (from the UK) or +44 1275 847787 (International).

After Sales Support

Biral offers free advice and technical support for the lifetime of the instruments we sell. Once you have purchased the unit you can contact us for help:

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