Observations
Surface observations by manned or automatic stations are the only direct confirmation of freezing rain. One can never see directly freezing rain, rain or snow on weather radars, Doppler or conventional. However, it is possible to estimate the area covered by freezing rain with radars indirectly.
The intensity of the radar echoes (reflectivity) is proportional to the form (water or ice) of the precipitation and its diameter. In fact, rain has much stronger reflective power than snow but its diameter is much smaller. So the reflectivity of rain coming from melted snow is only slightly higher. However, in the layer where the snow is melting, the wet flakes still have a large diameter and are coated with water so the returns to the radar is much stronger.
The presence of this brightband indicates that there is a warm layer above ground where snow melts. This could be producing rain on the ground or the possibility of freezing rain if the temperature is below freezing. This artifact can be located, like on the image at left, with a cross-section through radar data. The height and slope of the brightband will give clues to the extent of the region where melting occurs. Then it is possible to associate this clue with surface observations and numerical models prediction to produce output such as the ones seen on television weather programs that divide radar echoes into rain, mixed and snow precipitations.
Read more about this topic: Freezing Rain
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