![]() However, if the pitcher is jogging towards the catcher, the catcher catches balls more frequently because the balls are less spaced out (the frequency increases). Assuming the balls travel at a constant velocity and the pitcher is stationary, the catcher catches one ball every second. Imagine a baseball pitcher throwing one ball every second to a catcher (a frequency of 1 ball per second). This variation of frequency also depends on the direction the wave source is moving with respect to the observer it is maximum when the source is moving directly toward or away from the observer and diminishes with increasing angle between the direction of motion and the direction of the waves, until when the source is moving at right angles to the observer, there is no shift. ![]() The received frequency is higher (compared to the emitted frequency) during the approach, it is identical at the instant of passing by, and it is lower during the recession. ![]() It is commonly heard when a vehicle sounding a siren approaches, passes and recedes from an observer. The Doppler effect (or Doppler shift), named after Austrian physicist Christian Doppler who proposed it in 1842, is the difference between the observed frequency and the emitted frequency of a wave for an observer moving relative to the source of the waves. This is only a component of the real speed (170 km/h). This sea clutter tends to remain in the same area and can therefore be distinguished from rain echoes, which generally move with the wind.The emitted signal toward the car is reflected back with a variation of frequency that depend on the speed away/toward the radar (160 km/h). They can often be tracked moving towards or away from port over a series of images.During strong winds and very rough seas, sea clutter may be visible off the coast out to a range of about 30 km. These appear as specks or short arcs (oriented perpendicular to the direction of the radar). On cold clear winter nights and mornings these echoes may become stronger or increase in number due to downward refraction of the radar beam.Ships are regularly observed over the sea. These usually show up as small, stationary or erratically moving specks, mostly over the higher ground of the Blue Mountains, Southern Highlands and Barrington Tops areas. People in the Newcastle, Hunter Valley and lower Mid North coast are therefore encouraged to refer to the nearer Newcastle radar, those in the Illawarra the Sydney (Appin) radar and users on the Southern Tablelands the Canberra radar.Non-meteorological Echoes: In most cases, processing of the radar signal removes permanent echoes caused by hills, buildings and other solid objects, but sometimes a few slip through. The high sensitivity of the radar will assist in the detection of drizzle and light shower activity over Sydney, the Central Coast and Blue Mountains, but, as with other radars, the curvature of the Earth may hide these usually shallow weather systems at longer range. ![]() Based on detecting echoes at an altitude of 3,000 metres, the radar coverage extends as far north as Bulahdelah and Scone, west to Mudgee and Bathurst and south to Goulburn and Ulladulla.Meteorological Aspects: The radar will readily detect thunderstorms and deep rain-bearing systems approaching from any direction, often at greater range than quoted above. The rough topography of the Great Dividing Range slightly compromises the radar's view to the west, but the coverage to the north, east and south is largely unobstructed. The Terrey Hills site, on the Hornsby plateau at an elevation of 195 metres above sea level, gives the radar an excellent view in all directions. Geographical Situation: The radar is located 18 km north of the Sydney CBD. Terrey Hills Weather Watch RadarNew South Wales NSW 33.7009°S 151.2098☎ 194m AMSL Location
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