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dBZ stands for ''decibel relative to Z''. It is a logarithmic dimensionless technical unit used in radar, mostly in weather radar, to compare the equivalent reflectivity (Z) of a radar signal reflected off a remote object (in mm6 per m3) to the return of a droplet of rain with a diameter of 1 mm (1 mm6 per m3).〔(【引用サイトリンク】 work = NWS JetStream )〕 It is proportional to the number of drops per unit volume and the sixth power of drops diameter and is thus used to estimate the rain or snow intensity.〔 With other variables analyzed from the radar returns, it will help to determine the type of precipitation, too. == Principle == The radar reflectivity (Z) of a cloud is dependent on the number (N) and size (D) of reflectors (hydrometeors), which includes rain, snow, graupel, and hail. It is expressed by: : As rain droplets have a diameter of the order of 1 millimetre, Z is in mm6m−3 (μm3), a quite unusual unit. By dividing Z with the equivalent return of a 1 mm drop in a volume of a meter cube (Z0) and using the logarithm of the result (because the values vary greatly from drizzle to hail), one obtains the dimensionless quantity dBZ: : dBZ values can be converted to rainfall rates in millimetres per hour using the Marshall-Palmer formula:〔(【引用サイトリンク】title=NWS NEXRAD )〕 : 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「DBZ (meteorology)」の詳細全文を読む スポンサード リンク
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