Clouds strongly modulate the gain and loss of energy at the surface, which in turn affects the surface fluxes of sensible and latent heat. In the shortwave, clouds generally cool the surface while in the longwave, clouds generally warm the surface. An overall goal of this project is to attempt to quantify the effects of clouds on the surface radiation budget over the GAPP region. This goal will be achieved through a surface cloud forcing function CF(S), based on the downward and upward radiative fluxes under clear and cloudy conditions, that will be calculated from analyses and models and be compared with CF(S) calculated from observations. Since the spatial and temporal distribution of cloudiness will be a major contributor to the variability of CF(S), our first step in this project is to depict and understand the variability of cloudiness over the US. We will compare the cloudiness in the International Satellite Cloud Climatology Project (ISCCP) to the cloudiness in the NCEP/NCAR reanalysis for the years 1983 to 1998 with a focus on the monthly and year-to-year variability.