Defining and Validating the Minimum Detectable Weather Signal for an X-band Weather Radar System

Minimum detectable weather signal (MDWS) is one of the key parameters when estimating the basic performance of any weather radar system. It describes how weak target can be detected by the radar at a certain range, or it can be used to solve the maximum range of detection for weather target having certain intensity.

Detected signal at the radar receiver is a combination of echo signal and thermal noise, and they both vary significantly from sample to sample. For this reason, certain threshold value for the signal to noise ratio (SNR) required for weather detection must be used. This threshold depends on the expected fluctuations of the echo signal, signal processing techniques used as well as false alarm rate (FAR) and probability of detection (POD) accepted. In the literature, there are theoretically computed values available for SNR required for different kind of fluctuations, FAR, POD and number of samples averaged.

In this study, the MDWS of a Vaisala WRS400 polarimetric X-band weather radar is examined. WRS400 is a compact radar system equipped with antenna mounted transceiver, solid state power amplifiers (SSPA) and Vaisala RVP900 signal processing technology. MDWS is first estimated using the conventional weather radar equation and the theoretical value of the SNR required from the literature. Benefits of certain signal processing techniques, such as enhanced reflectivity computation are also considered. After this, the actual performance of the installed WRS400 system is verified by analysis of actual weather data. Results show that the theoretically calculated MDWS is well.