The part of the radiation where solar radiation is used by green plants and produces organic matter is called photosynthetically active radiation. In the past three decades, many scholars in China have done many researches and discussions on the observation of photosynthetically active radiation and climatological calculations. The study of agricultural climate provides a basic scientific basis. Based on our country is a mountainous country, the development and utilization of mountain slope resources is an important direction for the development of agriculture, forestry, animal husbandry and sideline production in China. Therefore, it is necessary to study the photosynthetically active radiation resources on the slope. The photosynthetic active radiation meter is an important instrument for effectively measuring the amount of radiation.
According to the photosynthetically active radiometer, it was found that in the mountainous areas, any slope is shielded by the surrounding terrain, resulting in a decrease in the photosynthetically active radiation of the sun reaching the slope. Because of the irregularity of the actual terrain masking, it is difficult to establish a good mathematical model. Therefore, it is difficult to calculate the shadowing effect of the surrounding topography on photosynthetically active radiation on the slope. However, it is not difficult to imagine that regardless of the complexity of the sheltered terrain, we can always determine an average shelter condition for a certain slope. Using this average shelter condition to discuss the effect of terrain on photosynthetically active radiation on a slope can simplify the problem.
The comparison of photosynthetically active radiometric measurements shows that, in fact, the effect of terrain obstruction on photosynthetically active radiation on slopes is mainly caused by obstructing direct solar radiation. Due to the effects of scattered radiation, the effect of terrain on photosynthetically active radiation on slopes is less than that on direct radiation on slopes. When the shading angle is late, the effect of photosynthetically active radiation on the slope is more significant. When the shading angle is less than 200, the effect of photosynthetically active radiation on the slope is less, the reduction is less than 5%; when 0<100, the reduction is even more significant. Less than 2 inches. In the actual undulating terrain, the sheltering of the surrounding hills on the sloping land is insignificant (most days < 20 ". Therefore, in the calculation of the photosynthetically active radiation on the actual sloping land, it is generally sufficient to consider only the influence of the sloping terrain parameters, which greatly Reduces the difficulty of calculating photosynthetically active radiation on slopes.
According to the photosynthetically active radiometer, it was found that in the mountainous areas, any slope is shielded by the surrounding terrain, resulting in a decrease in the photosynthetically active radiation of the sun reaching the slope. Because of the irregularity of the actual terrain masking, it is difficult to establish a good mathematical model. Therefore, it is difficult to calculate the shadowing effect of the surrounding topography on photosynthetically active radiation on the slope. However, it is not difficult to imagine that regardless of the complexity of the sheltered terrain, we can always determine an average shelter condition for a certain slope. Using this average shelter condition to discuss the effect of terrain on photosynthetically active radiation on a slope can simplify the problem.
The comparison of photosynthetically active radiometric measurements shows that, in fact, the effect of terrain obstruction on photosynthetically active radiation on slopes is mainly caused by obstructing direct solar radiation. Due to the effects of scattered radiation, the effect of terrain on photosynthetically active radiation on slopes is less than that on direct radiation on slopes. When the shading angle is late, the effect of photosynthetically active radiation on the slope is more significant. When the shading angle is less than 200, the effect of photosynthetically active radiation on the slope is less, the reduction is less than 5%; when 0<100, the reduction is even more significant. Less than 2 inches. In the actual undulating terrain, the sheltering of the surrounding hills on the sloping land is insignificant (most days < 20 ". Therefore, in the calculation of the photosynthetically active radiation on the actual sloping land, it is generally sufficient to consider only the influence of the sloping terrain parameters, which greatly Reduces the difficulty of calculating photosynthetically active radiation on slopes.
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