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Show Nl l( where K ~a M 2 - 1 - -- --- = (4) M2 + 2 ~1 and m is the refractive index of the scatters. The factor 10 - l 2 is used so that Z and N may be expressed in their conventional units of mm 6 /m 3 and cm -1 , respectively. Substituting the quantities for N and V into equation 1 we have: z = 512 P r \ 2 R 2 t 10 12 (5) The estimate for snowfall intensity may then be obtained from the relationship: (6) where c1 and c2 are empirical constants and I is in mm/hr. Radar ·calibration procedures that were used to determine appropriate values of the radar constants are described in Appendix B. 2. 5. 2 Method of Obtaining Data In the Park Range program, rather than using photographs to estimate precipitation intensity, the AGC voltage was used, as described by Handman and Davis (1964). The Automatic Gain Control (AGC) voltage is related to the power rec e ived by the radar. Essentially, the AGC circuit is a sample hold circuit in which the gain of the receiver is adjusted to a certain value dependent upon the amount of signal samp l ed in the range gate. In practice the amount of signal in the range gate (. 2 5 micro sec. ) adjusts the receiver gain until the arrival of another range gate. In the Park Range program a dual channel recorder was used to record the AGC voltage and slant range. In practice vertical profiles or slices were taken along selected azimuths as follows: ( 1) A particular azimuth was selected, generally dependent on the wind direction. (2) The antenna was pointed in the vertical direction and an aided 21 |