Modeling of rainfall enhancement by seeding tropical convective clouds

Convective clouds are characterized by strong updrafts, enhanced transport of heat and moisture in the upper layers and rainfall processes which are activated in very limited time interval and space and with a variable intensities. The cloud seeding for rain enhancment of such clouds is a big challenge and common practice in many areas over the world for more than 50 years. There is a strong scientific evidence and assessment on the status of weather modification from literature (see List et al, (1993), Cotton and Pielke (2007), Rosenfeld and Woodley, (1989, 1993); Silverman (2001), Levin and Cotton (2008). Over the years, there have been a number of projects which showed a more or less confidence for a rain augumentation by applying static glaciogenic seeding of cumulus convective clouds (e.g. Isaac et al. (1982), Dennis, 1980; Mason, 1982; Silverman, 1986; Cotton, 1986 and many others) A comprehensive analysis by Kessler et al. (2007, in Hebrew) and a subsequent summary by Sharon et al. (2008) concluded that seeding enhanced the amount of precipitation by about 30% in storms that produced less that 5 mm per day in Israel. In recent years models become a powerfull tools in weather modification research. Well-designed scientific experiments that include extensive measurements and model simulations are needed to determine whether artificial seeding can modify cloud structures and the effects of the seeding on precipitation enhancement Farley et al (1994); Bruintjes, (1999), Reisin et al., 1996; Cotton et al. (2006), Curic et al. (2007) and many others.