Ab. Long et Ej. Carter, AUSTRALIAN WINTER MOUNTAIN STORM CLOUDS - PRECIPITATION AUGMENTATION POTENTIAL, Journal of applied meteorology, 35(9), 1996, pp. 1457-1464
Two Australian winter mountain storm field research projects were cond
ucted by the Commonwealth Scientific and Industrial Research Organisat
ion Division of Atmospheric Research and the Desert Research Institute
Atmospheric Sciences Center in the austral winters of 1988 and 1990.
These projects gained information about winter storms in support of th
e ongoing Melbourne Water randomized cloud seeding experiment aimed at
increasing runoff into Melbourne's main water supply, the Thomson Res
ervoir. This paper discusses some of the 1988 instrumentation data. On
e variable of interest is the precipitation augmentation potential eta
. It is the difference between (a) the horizontal supercooled liquid w
ater flux in the clouds crossing the mountains and (b) the vertical pr
ecipitation flux at the surface from the clouds. These fluxes are base
d on calculations of supercooled liquid water depth in clouds with a m
icrowave radiometer, Omegasonde wind velocity, and rates of precipitat
ion from gauges. It was found that a varies systematically during a wi
nter storm. The greatest potential occurs in the post-cold-frontal sta
ge of a storm when the cloud-top temperature is warm and about -12 deg
rees C and the wind direction of 240 degrees is approximately orthogon
al to the main southwest face of the predominant orographic feature, B
aw Baw Plateau, of the study area. The potential is significantly less
during the prefrontal and frontal stages, with cloud-top temperatures
of about -35 degrees C and a wind direction of about 300 degrees para
llel to the Baw Baw Plateau. The results show that cloud seeding would
have the greatest benefit in the postfrontal stage.