Weather radars are radar systems which measure the intensity of precipitation by means of electromagnetic waves.
The work group of radar and microwave propagation has been involved in this topic for many years starting with the design and implementation of the research weather radar Hilmwarte by Joanneum Research as part of the habilitation treatise of Prof. Dr. Randeu, the former head of the work group. After that we started the development of the WIIS software package (at the beginning only for visualisation of the images of the radars of Austro Control GmbH.). In the last years we participated in the development of a small scale weather radar within the framwork of the EU-project MARG.
A weather radar is typically a so-called pulsed radar, which means that it transmits a short high power and high frequency electromagnetic pulse. This pulse will be scattered by precipitation particles causing a part of the energy to be reflected back to the radar receiver. The strength of this echo signal - while also considering the measured distance to the target objects - is a measure for the intensity of the rain.
Modern systems are also able to evalute the Doppler effect and can therefore determine the velocity (along the direction to the antenna) of the particles.
Polarimetric weather radars measure both the reflectivity of horizontal and vertical polarised waves and can therefore determine the shape of the particles.
The Austro Control GmbH. (Austrian's air-traffic control service provider) runs a network of 5 weather radars in Austria :
Those radar systems are operating in C-Band (about 5620 MHz) and each has a maximum range of 250 km.
A radar needs 5 minutes for the completion of a volume scan.