GNSS polarized signal forward modeling method and system suitable for light rain magnitude

The invention discloses a GNSS polarized signal forward modeling method and system suitable for light rain magnitude; the rainfall rate of light rain is less than or equal to 2.5 mm/h, and the method comprises the steps: obtaining rainfall information in a light rain area to be measured, wherein a GNSS polarization radio occultation event occurs in the light rain area, and the ray path of occultation passes through the rain area; respectively establishing a raindrop shape model and a raindrop spectrum distribution model; calculating the relative complex permittivity of raindrops; calculating the horizontal polarization forward scattering amplitude and the vertical polarization forward scattering amplitude of a single raindrop in combination with the raindrop shape model; calculating differential phase delay according to the raindrop spectrum distribution model and the horizontal polarization forward scattering amplitude and the vertical polarization forward scattering amplitude of the single raindrop; and int