Doppler distrometer for the measurement of hydrometer size distribution
First Claim
1. An apparatus for determining a size distribution of hydrometeors, comprising:
- source means for providing continuous wave radiation;
reflecting means coupled to said source means for directing said radiation toward said hydrometeors;
receiving means cooperating with said source means for receiving radiation reflected by said hydrometeors;
detector/filter means coupled to said receiving means for converting said reflected radiation into a first signal constituting a velocity spectrum of said hydrometeors;
recording means for recording said first signal in electrical form; and
transforming means coupled to said recording means for transforming said first signal into a signal constituting said size distribution of said hydrometeors.
1 Assignment
0 Petitions
Accused Products
Abstract
An apparatus and method are disclosed which employ the Doppler principle to measure the terminal velocity and, hence, the size distribution of hydrometeors such as raindrops and hailstones. The apparatus of the present invention employs a ground-based, upwardly directed, low power, 10.525 GHz homodyne continuous wave radar module to transmit microwave signals to falling hydrometeors within the size range of 0.5 mm through 4.0 cm, to record the frequency distribution and power spectrum of the reflected signals, and to process these data with "terminal velocity"-to-"hydrometeor diameter" calibration data to generate information on the hydrometeor size distribution in the precipitation under observation. The disclosed method permits a user of the apparatus to select the Doppler velocity threshold above which data are recorded for processing with a Fast Fourier Transform technique to determine hydrometer velocity values.
23 Citations
17 Claims
-
1. An apparatus for determining a size distribution of hydrometeors, comprising:
-
source means for providing continuous wave radiation; reflecting means coupled to said source means for directing said radiation toward said hydrometeors; receiving means cooperating with said source means for receiving radiation reflected by said hydrometeors; detector/filter means coupled to said receiving means for converting said reflected radiation into a first signal constituting a velocity spectrum of said hydrometeors; recording means for recording said first signal in electrical form; and transforming means coupled to said recording means for transforming said first signal into a signal constituting said size distribution of said hydrometeors. - View Dependent Claims (2, 3, 4, 5)
-
-
6. A method for determining the size distribution of hydrometeors, comprising the steps of:
-
projecting continuous wave homodyne radiation toward a volume occupied by said hydrometeors; receiving radiation reflected by said hydrometeors; converting said reflected radiation into a first signal constituting a velocity spectrum of said hyrometeors; and transforming said first signal into a second signal representing a size distribution of said hydrometeors. - View Dependent Claims (7, 8, 9, 10, 11)
-
-
12. A method for determining the size distribution of hydrometeors, comprising the steps of:
-
projecting continuous wave homodyne radiation toward a volume occupied by said hydrometeors; receiving radiation reflected by said hydrometeors; converting said reflected radiation into a first signal constituting a velocity spectrum of said hydrometeors; recording said first signal; applying a Fourier Transform to said recorded first signal; and applying a velocity-to-size calibration transform to said Fourier transformed first signal to transform it into a second signal representing a size distribution of said hydrometeors.
-
-
13. A system for recording echo signals indicative of the velocity spectrum of falling hydrometeors so that data indicative of the size, velocity and distribution of said falling hydrometeors may be derived from the recorded data, which comprises the combination of:
-
radar means for illuminating a volume which may contain falling hydrometeors and for receiving echoes therefrom which are Doppler-shifted in frequency due to the velocity and cross section of the falling hydrometeors; sampling means for intermittently energizing said radar means repetitively to initiate sample intervals of selected time duration during which said radar means is active; means for producing an audio signal from said Doppler-shifted echoes which represents the velocity spectrum of said falling hydrometeors; means having said audio signal as an input for generating a dc voltage signal from the frequency spectrum of said audio signal; and threshold means for extending said sample intervals when said dc signal exceeds a predetermined value indicative of the presence of falling hydrometeors having a selected threshold velocity. - View Dependent Claims (14, 15, 16, 17)
-
Specification