Snowfall Rate Estimation Using X-band Dual-Polarization Radar

For effective water resource management in the western United States, accurate estimates of snow water equivalent (SWE) are desirable. However, there are significant challenges facing the SWE estimation in complex terrain using weather radars especially at short wavelengths. Challenges include but are not limited to direct observational characteristics of snowflakes, severe beam blockages precluding radar observations near the surface, and attenuation of radar reflectivity. This paper presents an SWE estimation study using X-band dual-polarization radar observations from a field experiment in south-central Colorado during the winter of 2014-15.

In the current study, reflectivity measurements from different tilts are applied at different locations for the SWE estimation to mitigate blockage effects. Dielectric constants of melting snow were calculated by modeling snow as a mixture of ice, water and air with various mixing ratios. The reflectivity attenuation coefficient was estimated through the T-matrix method assuming an exponential snow particle size distribution. SWE was then derived from the corrected reflectivity Z. The SWE estimates were compared with surface gauge measurements and showed a reasonable agreement.