Rainfall estimation using a microwave link based on an improved rain-induced attenuation model

Theoretical analyses show that both the rain-induced attenuation of electromagnetic signals and rainfall intensity are relative to the raindrop size distribution (DSD). In this paper, an improved rain-induced attenuation method is proposed to enhance the rainfall estimation accuracy through microwave links. The model is established through nonlinear fitting with the local DSD measured in Nanjing, China. The method for calculating the rain-induced attenuation of the microwave links is presented based on the calculation of the microwave path loss, air attenuation, and instrument attenuation. Data from an experiment with a 6.57-km microwave link of 15–20 GHz in Nanjing are used to test the improved model. The rainfall intensity estimation and rainfall depth determined by the proposed model is closer to the disdrometer measurement than is the estimation by the specific attenuation model of the International Telecommunication Union (ITU). Results from the experiment indicate that the proposed model has higher accuracy with respect to rainfall estimation and is feasible in practice. Therefore, it is essential to establish the local rain-induced attenuation model when estimating rainfall using microwave links.