This paper consists of three parts. The first part is concerned with the parameterization of cloud microphysics in climate models. We demonstrate the crucial importance of spectral dispersion of the cloud droplet size distribution in determining radiative properties of clouds (e.g., effective radius), and underline the necessity of specifying spectral dispersion in the parameterization of cloud microphysics. It is argued that the inclusion of spectral dispersion makes the issue of cloud parameterization essentially equivalent to that of the droplet size distribution function, bringing cloud parameterization to the forefront of cloud physics. The second part is concerned with theoretical investigations into the spectral shape of droplet size distributions in cloud physics. After briefly reviewing the mainstream theories (including entrainment and mixing theories, and stochastic theories), we discuss their deficiencies and the need for a paradigm shift from reductionist approaches to systems approaches. A systems theory that has recently been formulated by utilizing ideas from statistical physics and information theory is discussed, along with the major results derived from it. It is shown that the systems formalism not only easily explains many puzzles that have been frustrating the mainstream theories, but also reveals such new phenomena as scale-dependence of cloud droplet size …

In Fiscal Year 2001, for the third year in a row, the solar electric market grew at more than 30%. Fueling this growth is the U.S. photovoltaic industry - the companies that design, manufacture, install, operate, and maintain all components of solar generating systems. The messages of the U.S. PV industry roadmap are taken very seriously by the U.S. Department of Energy's Office of Solar Energy Technologies. Achieving industry's goals will demand aggressive work in fundamental and exploratory research, manufacturing, and system applications to reduce the cost of solar electric systems. This is an annual report of the DOE PV Program, FY2001.