Based on the spectral irradiance database (ver-3) for all weather conditions published by the New Energy and Industrial Technology Development Organization (NEDO), the relationships among spectral irradiance, total solar radiation, sunshine rate, and solar altitude were investigated. These data are recorded by Japan Weather Association(JWA) every 10 minutes from sunrise to sunset. The data processing method is the same as before report. For each of the five stations (Naganuma, Tsukuba, Gifu, Tosu and Okinoerabu), the spectral solar radiation was estimated by using normalized spectral solar radiation (HYst), weather factor (Fw), and peak wavelength spectral insolation Ip (λp). The peak wavelength spectral solar radiation (Ip) is estimated from the total solar radiation (HQH) using a regression equation. As a result, under non-rainfalling weather conditions, the estimated of the spectral solar radiation and the estimated errors for twelve months at five stations were clarified.
