Micro Rain Radar for profiling precipitation

The vertical pointing Micro Rain Radar is able to detect 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.

Tripod mounted MRR	Close up of MRR	Example of graphical data output
Click to expand pictures in new window

Features

• 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

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

The radar dish is the largest component of the unit and is the same size as a typical home satellite dish (60 cm). Attached is a small electronics box that houses the entire transmitter and receiver electronics and does some very basic processing on the received data. 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.

The component parts please click image to expand in new window	Dimensions please click image to expand in new window
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

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.

Outdoor Components

• Offset parabolic dish antenna, Ø 60 cm, beam width 2 °, 6 dB
    
• Radar front end (electromagnetic feed), Ø 8 cm x 10 cm connected to transmitter control electronic housing

  
  

  Frequency: 24.1 GHz (24.1GHz - 24.15GHz) or 10 GHz

  Modulation: saw tooth type, modulation depends on adjusted height resolution:
  
  for example 1.5 MHz for 100 m height steps
  for example 3 MHz for 50 m height steps

  Radiated Power: 50 mW

  Power Consumption: 25 W @ 24 VDC
     

• Transmitter control electronic housing, 26 cm x 16 cm x 10 cm, IP65
   
• Receiver unit and digital signal processor unit for FFT (Fast Fourier Transform) - analysis for derivation of Doppler spectra (10 s sampling time), also housed in the above transmitter control electronic housing unit.
   
• Data transmission with RS232 or RS422 interface for system control
   
• 25 m junction cable for data transfer and power supply of outdoor components

Indoor Component

• Power supply - you can use either mains power (100 - 240 VAC) or 24 VDC as both types are available as standard.

PC based software is available for online control, data visualisation, transfer and storage. Two programs are included; MRR control and Metek Graphics program.

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Specifications
(Vertical Pointing Complete Micro Rain Radar - MRR-2, FMCW Mode)

Software

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

System Parameter:

• Sampling time: 10 s *
• Average time: adjustable, 10s to 1800s
• Number of height steps: adjustable, max.30
• Height steps:adjustable, 10m to 200 m
• Lowest usable measuring height: 2 height steps
• Automatic restart after power breakdown with no loss of settings
• Output of measured data (spectra, reflectivity, rain rate, liquid water content) both as instantaneous and averaged data (with selected averaging interval)
• Software module is for system access and control, data transfer and data storage.

* 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.

Graphic-Software

• 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.

Click here to see examples of graphical output

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Computer

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 (see below for computer specifications).

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.

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We hope this information has been useful - for further information please check out the links at the bottom of the MRR main page.

E.&O.E.  ©