ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Impact Analysis of Sunshine Records Owing to Obstructions Around the Observational Field
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Abstract:
Both the angle of solar altitude and the orientation of the sun at sunrise and sunset in the observing stations located in the Equator, stations between the Equator and the Tropic of Cancer, stations at the Tropic of Cancer, and stations north to the Tropic of Cancer are calculated and analyzed respectively. The scale of sunshine records affected by the obstruction is decided on the basis of the above analysis. In an example of Yichang observing station（30°42′N，111°18′E）, the procedures to analyze the scale of sunshine records affected by the obstructions are given, which will not only be a helpful guidance for observing stations to calculate the scale of sunshine record affected by the obstruction, and but also be a useful example for deciding the location of solar radiation and sunshine duration observing instrument. In the examples of Guangzhou （23°10′N，113°20′E）, Yichang（ 30°42′N，111°18′E） and Beijing （39°48′N，116°28′E） observing stations, the days and dates when the sunshine records are affected, and annual maximum sunshine duration and sunshine percentage which are possibly affected are also calculated, and therefore, the rules how the obstruction affects the record in different directions and with the change of latitude are found. The result shows that the azimuth of the sun in China varies from 37°to 143° at sunrise and from 217°to 323° at sunset. Any obstructions located in the azimuth between 323°and 37° （northeast or northwest） can not affect the sunshine record. Obstructions located in a certain area in the south, southwest or southeast are not prone to affect the sunshine record since the solar altitude angle is usually very high. Maximum sunshine duration affected by obstructions which have the same altitude and the orientation increases with the increasing latitude. The degree that obstructions located in the mostly affected direction affect annual sunshine percentage is basically similar.
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