RADAR system

The Radio Detection And Ranging (RADAR) system allows us, using electromagnetic waves, to detect the presence of targets and measure its distance and speed respect to the observation point. The targets can be any object stationary or in movement, such as air planes, ships or as the case of this project: hydrometeors (Snowflakes, raindrops, hail, etc.). Weather radar corresponds to the radar used to analyze the precipitation and determine the location, speed and direction of its motion. The response time of a signal emitted by the antenna depends on the speed and the distance of the observed targets and the backscattered power is related to hydrometeors size.

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Fig. 1. Working principle of a weather radar. Pulse (Up) and Continuous Wave radar (Down). NOAA.

The working principle of the radar system (fig. 1) consists of the emission of a microwave beam from a “transmission antenna”, which is partially reflected by the targets and received back by a “receiver antenna”, which can be the same antenna used for the transmission. Subsequently, the signal is recorded and processed by an electronic system. The most used method in weather radar to detect and determine the speed of a target respect to the antenna is the Doppler effect, which consists in the apparent change of the frequency of a wave produced by the relative movement of the source (backscattered signal from the hydrometeors) with respect to its observer (radar antenna). Variations of the frequency of a signal emitted by the antenna will depend on the speed of the observed targets. The response time of a signal emitted by the antenna depends on the speed and the distance of the observed targets and the backscattered power is related to hydrometeors size.

During the last mission at Dumont D’Urville station (DDU) (See Campaign 2015-2016) two radar systems were deployed during the summer, a volumetric dual polarization radar in X-band (MXPol) and a vertical pointing radar in K-band (MRR-2). The MRR-2 is still installed at DDU inside of a dome (radome) with a full year of records. In the current mission at DDU, we are going to deploy a second MRR-2 without a radome in order to determine the effect of it on the signal.

Micro Rain Radar (MRR-2)

The MRR-2 is a low-cost vertical radar profiler designed by Metek, which provides drop size distribution, rain rate, liquid water content, fall velocity and more recently snow measurement thanks to efforts of developing improved post-processing methods, such as Kneifel et al. (2011) and Maahn and Kollias (2012).

MRR-2 works with a transmit power of 50mW and at a frequency of 24 GHz in the Frequency Modulated Continues Wave Mode (FCWM). Is has a adjustable time and height resolution, with a maximum height of 6000 meters and 30 vertical bins above the ground.

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MRR-2 tested at the roof of OSUG-B (LTHE).
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