چكيده لاتين :
Atmosphere is a dynamic fluid in which natural processes such as movement
of air mass, formation of natural cloud and precipitation occur, and where
weather modification is focused on possibility of control on natural processes
of atmosphere. Cloud models have different types of application in operational
weather modification programs such as; hypothesis development, assessment of
seedability, experimental design, operational decisions, project evaluation, as
well as understanding of seeding effects. Therefore, in this research, numerical
modeling for optimal utilization of phase change energy in ice thermal induced
by Liquid Carbon Dioxide (LCD) in supercooled cloud seeding as suggested
in Javanmard et al. (1998a) has been applied. In this article, after a short
review on application of numerical modeling in weather modification activities,
numerical modeling of the Roll-up Expansion of Twin Horizontal Ice crystal
Thermal (RETHIT) process which forms in LCD seeding has been presented.
It includes the dynamics, microphysics, and procedure of calculation of the
model. Then in order to assess optimal seeding rate in supercooled cloud seeding
using LCD, the above mentioned RETHIT numerical model which is written
in Fortran language has been applied. The model has been run for the three
seeding rates of (PL) 40 gis, 100 gis, and 260 g/s. Finally, the output results
of the microphysic and dynarn.ic parameters of the formed ice thermal has been
discussed.
The above mentioned results of the numerical model has shown that the
arriving time of ice thermal at the cloud top is about 16 min in PL=40, 15.4
min in PL=100, and 17.2 min in PL=260. which is very close to the LCD
seeding experiment results which have been obtained by Tomine et al. (1998);
they ere also in accordance with the metaldehyde seeding experiment results
obtained by Fukuta (1972). As a result, the calculated optimum seeding rate
by LCD seeding model is 40 s/». which could help in determining the threshold
value of seeding rate, and which avoids overseeding effects as well as economic
benefits.
