Darwin Harbour Rain Radar

The Berrimah radar is located on a rise with the dish antenna tower mounted app roximately 50 metres above the surrounding topography. It has a good coverage in all directions up to a range of 250 km with the following two exceptions: (a) some local masking of echoes at low elevations to the east; (b) some signal blockage to the north-northeast due to several HF transmitter towers. Heavy rain over the radar site will cause attenuation of all signals. Path atte nuation also occurs when the radar beam passes through an intense thunderstorm cell; the returned signal from cells further along that path will be reduced. Because the beam width of this particular radar is only 0.9 degrees, it may 'undershoot' high level storms and rain echoes may appear less intense than actual rainfall rate. During the dry season from May to September, when low level atmospheric tempera ture inversions are more prevalent, images may display areas of relatively strong (Level 2 or 3) permanent echoes. These tend to be reflections from coastal features; commonly from Gunn Point and the Cobourg Peninsular northeast of the radar, and from the nearside coastline of the Tiwi Islands to the north. Also during this time of the year, a false image of the Timor coastline may sometimes be seen extending northwest from Bathurst Island. This phenomenon is due to second skip returns at multiples of the radar's maximum range. <a