Research on Influence of Station Occlusion on Consistency of Sunshine Observation Data and Its Correction Method
Based on the observation data of 360° occlusion elevation angle and cloud amount around the observation site, the influence of occlusion on the consistency of sunshine observation data is analyzed. From the relative relationship between the solar elevation angle and the occlusion elevation angle, and the correction of the cloud to the occlusion rate, the correction method of the occlusion sunshine hours by station under cloudy weather conditions is established. Take Wushan Station in Chongqing as an example. The calculation and correction of the sunshine hours during the period of severe occlusion from 2004 to 2013 is performed. Through the vertical comparison between the occlusion period and the two unoccluded periods before and after the occlusion and the same-period horizontal comparison of Jianshi Station in Hubei Province, which is similar to the terrain and climate conditions, the correction effect is tested. The results show that the obstructions around the observation site of Wushan Station affect the observation of sunshine hours， which makes the observation data inconsistent before and after the occlusion. During the period of 2004-2013, the average number of occluded sunshine hours was 218.0 h·a-1, and the occlusion ratio reached 13.1%. Due to the hedging effect of weather conditions, the influence of occlusion in summer half year may be higher than that in winter half year. From the indirect comparison between the vertical and horizontal aspects, the correction method established in this paper not only calculates the influence of the occluder itself, but also takes into account the correction of the occlusion ration under cloudy conditions. The correction results are basically reasonable, and can be relatively accurately restore the occluded sunshine hours.