Research On A Novel Sunshine Duration Recording System With Light-Shadow Image Processing

The sunshine duration is an element of surface meteorological observation. For measuring sunshine duration, it is need to determine whether the ray is direct light and whether its irradiance is more than or equal to a defined threshold. Existing sunshine duration recorders and measuring methods have some inadequacies. Aimed at this problem, this paper researched on a novel sunshine duration recording system with the image acquisition and processing.First, the diffraction intensity formulas for some light incidenting on a grid translucent plane were deduced and analyzed, also the straight edge diffraction intensity formulas for direct and scattered light. The feasibility and method for measuring sunshine durations by processing images were defined. And the working principle of the light-shadow sunshine duration recording system was proposed. The integral structure of this system and Matlab processing program were designed. And last, testing experiments were done for analyzing the performance of the system.The main results in this paper are as follows.(1)A light-shadow sunshine duration recording system was developed. The system is composed of exposed object, display surface, image collector and computer image processing system. The system collects and processes an image, and accumulates time intervals for capturing the image in sunshine durations when the brightness and edge sharpness are not respectively less than the values of the image for the direct ray of120W·m-2.(2) The Matlab processing program can show the real-time measurement automately. The standard compared values of brightness and shadow edge sharpness are215and16.3respectively.After a probationary, this system runs stably. It is easy to install and can display the real-time measured results in every hours, also the start moment and end moment of the sunshine.