Path-averaged rainfall estimation using a microwave link: uncertainty due to rainfall spatial variability

Microwave links offer the possibility to estimate (1) the latent and sensible heat fluxes between land-surface and atmosphere, as well as (2) the path-averaged rainfall intensity along the link when precipitation occurs. In the latter case, a power-law relation is assumed between the specific attenuation k affecting the electro-magnetic signal while propagating through precipitation and the rainfall intensity R, variable of interest for many hydrological applications. This work focuses on the influence of the spatial variability of rainfall along the link on the parameterization of the k-R relation, at the point and link scale. A stochastic model is used to generate range profiles of raindrop size distributions and subsequently to simulate link measurements. A Monte Carlo technique is then applied to quantitatively analyze uncertainties on the k-R power-law parameters for a range of operating frequencies between 10 and 100 GHz and for different types of rainfall events.