Estimating Absolute Humidity Using Latency Measurements over CMLs: Challenges, Opportunities and Error Analysis

In recent years measurements of the attenuation in Commercial Microwave Links (CMLs) have been used for monitoring atmospheric phenomena, and in particular rain and absolute humidity (AH). In this work, we present a method for estimating absolute humidity using measurements of the propagation delay in a CML. Using real data we show that although the refractive index of the propagation channel, which is responsible for the delay, depends on the temperature and barometric pressure as well as on the absolute humidity, measurements of the propagation delay are sufficient for reliable estimation of the absolute humidity even when the corresponding measurements of the temperature and pressure are not provided. Theoretical error analysis of the AH estimates is also presented, showing good agreement with the empirical results.