Signal Analysis and Quality Control of Microwave Links for Rainfall Measurement

As a new method of rainfall measurement, Microwave Links (MLs) can be used to inverse the rainfall intensity according to the rain-induced attenuation in atmosphere. It is of great significance to improve the real-time monitoring and timely warning of rainfall in a large area. However, compared with the rain gauge and weather radar, the reliability and performance of rainfall measurement using microwave links still need to be further verified. Firstly, we have obtained reliable rainfall intensity data measured by OTT disdrometer, and according to the threshold value we set, we can distinguish rainy days from non-rainy days. Secondly, the obtained microwave link signal data is preprocessed. We choose the wavelet denoising method with the best effect from some denoising methods. Then the correlation coefficient between the rainfall intensity data and the microwave link signal data on rainy days is calculated, and it is found that there is a strong negative correlation between the two, and the correlation can be improved to some extent by denoising. In order to validate that rainfall does cause the attenuation of microwave link signal, the mean value and variance of microwave link signal data on rainy days and no rainy days are compared and analyzed, and it is found that rainfall is the main reason for the significant attenuation of microwave link signal. After denoising, when the mean value of the signal does not change significantly, the standard deviation becomes smaller, indicating that noise reduces the effectiveness and quality of the microwave link signal. Therefore, denoising processing is also an essential part of the microwave link rainfall measurement method.