Estimation of Melting Layer Altitudes From Dual-polarization Weather Radar Observations

The melting layer is a significant phenomenon in weather radar observations. It is known to be variable in space and in time, in many climates. The altitude of melting layer (MLHGT) is a parameter in interpretations of weather radar observations, such as hydrometer identification and quantitative estimates of surface rainfall. Significant uncertainty may be introduced in these applications by the uncertainty in MLHGT estimates.

We have developed and implemented a method for estimating MLHGT from observations of dual-polarization Doppler weather radar. The method builds on the well-established capability of dual-polarization to detect melting snow, gate-by-gate. The MLHGT estimates are obtained at configurable spatial and temporal resolution, adapting automatically to the radar resolution which degrades as function of range. The method is designed for near-real-time operational uses and the outcomes can be used as input to multiple applications.

The MLHGT method has been evaluated in conditions of warm and cool season, with direct validation with respect to independent upper air soundings. The MLHGT estimates, the estimates of their uncertainty and of radar confidence are found to perform consistently. The remote MLHGT estimates of high radar confidence agree at the level of hundred meters with the estimates derived from temperature profiles of in-situ soundings.