Remember that due to the Earth's curvature, the radar beam becomes higher above Your nearby radar image is affected by any interference. Kilometres of the radar site, but mountain ranges further away can sometimesĬheck the radar site information to see if Permanent echoes are created when the radarīeam reflects off ground features and buildings, normally within about twenty The radar may sometimes detect faint echoes from non-precipitation targets suchĪs aircraft, areas of smoke/ash from large fires, swarms of insects, flocks ofīirds or even the surface (when unusual atmospheric conditions bend the radarīeam back down to the surface!). Why does the radar show that it is raining when it is dry where I am? The latter rain clouds typically consist of very large raindropsīut much less in number. Reflectivity is much less than for similar rainfall rates in continental area Maritime rainfall consists of very many moderate sized raindrops so that the The radar reflectivity is strongly dependent on the diameter of raindrops in theĬloud not the amount of rain drops and therefore rainfall rates. Why is there a difference between the rainfall measurements and the colours Radar imagery should be used only as a very rough guide. Consequently the estimation of rainfall rates using the Refractive index of the air, attempts to correct for these limitations have notīeen very successful. Because of the variations in rain closer to the radar site and in the Whole of the radar beam, thus significantly reducing the echo intensity fromģ. The presence of mountains within the range of the radar can block part or Where the relationship between reflectivity and rainfall rate is different.Ģ. Radar echoes are likely to be reflections caused by ice rather than rain drops, The presence of significantĮchoes at large range probably indicates the presence of large amounts of rainĪt high levels above the ground (e.g. Show at all, or may show with a reduced intensity. Thus precipitation that is occurring some distance away from the radar might not Reducing the echo intensity further out from the radar. With practice, however, you will find them useful.Ĭ) The beam can lose power slightly when passing through very heavy rain, thus Ranges can be difficult and you should take great care in using these images. As a result, the radar image will not show any rainĮven though at the ground level it may be raining at the time.ĭue to the reasons described above, interpreting the radar images at extended In winter especially, the rain clouds can be below the radar beam at aĭistance of more than 200 kilometres from the radar, and hence the radar beam Raindrops at a height of 3 kilometres from rain that is 200 kilometres away, andĪt a height of around 7 kilometres at a distance of 500 kilometres from the Surface from rain that is 100 kilometres away from the radar. Radar beam detects raindrops at a height of 1 kilometre above the Earth's Of the Earth's curvature, and partly because the beam is angled upwards by aįraction of a degree), thereby missing the lower parts of the rain. The intensity of echoes tends to decrease with increasing distance from theĪ) The radar beam broadens with distance, thus decreasing the proportion of theīeam which is filled with rain, which reduces the echo intensity ī) The radar beam becomes further from the ground with distance (partly because The effects of the curvature of the earth on weather radar.ġ. The Images Why is the radar showing no rain when it is raining where I am?
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