Abstract

It has previously been shown that the scintillations produced by raindrops falling through a collimated laser beam can be used to measure the drop-size distribution and the rainfall rate, both averaged over the path. We now present a theoretical analysis, verified by observation, showing that the variance of the scintillations detected by a line-detector measured at frequencies near 1 kHz is closely related to rain rate and is nearly independent of drop-size distribution. If only rain rate is desired, the variance type of optical rain gauge has several advantages over the earlier model. It could use a diverging beam, thus eliminating the practical difficulties of maintaining adjustment and pointing of a collimated beam. Furthermore, it is less sensitive to the presence of updrafts and downdrafts along the beam and can thus be used over rough terrain.

© 1978 Optical Society of America

Measurement of rain parameters by optical scintillation

Ting-i Wang, G. Lerfald, R. S. Lawrence, and S. F. Clifford
Appl. Opt. 16(8) 2236-2241 (1977)

Optical rain gauge using a divergent beam

Ting-i Wang, R. S. Lawrence, and M. K. Tsay
Appl. Opt. 19(21) 3617-3621 (1980)

Use of rainfall-induced optical scintillations to measure path-averaged rain parameters

Ting-i Wang and S. F. Clifford
J. Opt. Soc. Am. 65(8) 927-937 (1975)

Measurement of rain parameters by optical scintillation: computer simulation of the correlation method

Ting-i Wang and R. S. Lawrence
Appl. Opt. 16(12) 3176-3179 (1977)

Laser rain gauge: near-field effect

Ting-i Wang, P. N. Kumar, and D. J. Fang
Appl. Opt. 22(24) 4008-4012 (1983)