Abstract
In this study, the numerical model was developed to evaluate the observational environment of sunshine duration and, for evaluating the accuracy and utility of the model, it was verified against the observational data measured at Dae-gu Automated Synoptic Observing System (ASOS) located in an urban area. Three-dimensional topography and building configuration as the surface input data of the model were constructed using a Geographic Information System (GIS) data. First, the accuracy of the computing planetary positions suggested by Paul Schlyter was verified against the data provided by Korea Astronomy and Space Science Institute (KASI) and the results showed that the numerical model predicted the Sun's position (the solar azimuth and altitude angles) quite precisely. Then, this model was applied to reproduce the sunshine duration at the Dae-gu ASOS. The observed and calculated sunshine durations were similar to each other. However, the observed and calculated sunrise (sunset) times were delayed (curtailed), compared to those provided by KASI that considered just the ASOS's position information such as latitude, longitude, and elevation height but did not consider the building and topography information. Further investigation showed that this was caused by not only the topographic characteristic (higher in the east and lower in the west) but also the buildings located in the southeast near the sunrise and the southwest near the sunset. It was found that higher building resolution increased the accuracy of the model. It was concluded that, for the accurate evaluation of the sunshine duration, detailed building and topography information around the observing sites was required and the numerical model developed in this study was successful to predict and/or the sunshine duration of the ASOS located in an urban area.
