Collocated Radar and Radiosonde Observations of a Double-Brightband Melting Layer in Northern California

Abstract A strong elevated temperature inversion in a landfalling winter storm in northern California produced two simultaneous melting layers with associated radar bright bands. The storm was observed with scanning and profiling radars. Serial radiosonde launches from the scanning radar site precisely documented the evolving temperature structure of the air mass that produced the double bright band. The radiosonde and radar observations, which were coincident in location and time, clearly illustrate the cause (two melting layers) and effect (two bright bands) of this unusual phenomenon. An automated algorithm for determining the melting-layer height from profiling radar data was tested on this situation. In its operational form, the algorithm detects only the lower melting layer, but in modified form it is capable of detecting both melting layers simultaneously.