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New dual-polarization Doppler weather radar at Tate’s Cairn

The Hong Kong Observatory commissioned a new dual-polarization Doppler weather radar to replace the old single polarization radar at Tate’s Cairn in early 2015 (Figure 1).

Unlike traditional single polarization radar, the new dual-polarization radar transmits two trains of electromagnetic (EM) wave with mutually perpendicular electric fields, i.e. different polarizations, simultaneously (Figure 2). As echoes bounced back by ice of various forms and rain drops of various sizes have different characteristics (Figure 3), by analyzing the differences in the echoes, an improved estimation of rainfall rates and occurrence of hail etc. can be achieved.


Fig. 1 Tate’s Cairn Weather Radar Station


Fig. 2 Working principals of single and dual-polarization Weather Radars


Fig. 3 Weather systems comprise rain drop and ice of various forms and shapes respond differently to EM wave of different polarization