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<br />I <br />I <br />I <br />I <br />I <br />'I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />1987). Exceptions to this were those times when it was down <br />during maintenance or the approximately weekly "tipping curve" <br />calibrations. This method provides updates of some of the <br />coefficients used in the computer software that can change <br />due to gradual shifts in atmospheric characteristics and electronic <br />component drift. Tipping curves can only be made in cloud-free <br />or totally ice-cloud conditions. <br /> <br />2.4.3 . <br /> <br />C-band Radar <br /> <br />A C-band (5.4 cm wavelength) radar, owned by the Bureau <br />of Reclamation, was operated at the Happy Jack site from mid-- <br />January through March 17, 1987. It arrived with the microwave <br />radiometer and was installed in about the same time frame. <br />Its primary purpose was to monitor cloud base and top altitudes <br />and the structure of the latter (stratiform, convective). <br />The system, known as the swa-86 Skywater radar, uses a micro- <br />processor for scan control. It transmits 250 KW peak power <br />and has a one degree beam width. Data are digitized and written <br />on 9 track magnetic tape for later analysis. <br /> <br />Except for infrequent periods when the radar operated <br />in the PPI (Plan Position Indicator) mode, scanning to ascertain <br />the aerial distribution of precipitation, the radar was operated <br />in the RHI (Range Height Indicator) mode, making one slow <br />sweep per 5 minutes. This provided data for cloud top and <br />base determination. Such radar information is normally provided <br />by pointing the antenna vertically. However, noise in the <br />first few kilometers from the SWR-86 radar required that RHI <br />scanning be used. <br /> <br />2-12 <br />