Solar irradiance-corrected spatial interpolation of hourly temperature in complex terrain

Abstract

Converting temperature forecasts and observations at irregular points into a gridded data set is widely used for regional scale ecosystem modeling and model-based decision making. Neglect of terrain effects in spatial interpolation schemes for short-term temperature assessment may cause erroneous results in mountainous regions, where the observation network ineffectively covers complex terrain. We suggest a spatial interpolation model for daytime hourly temperature based on an error analysis of unsampled sites with respect to the site topography. The model has a solar irradiance correction scheme in addition to the common backbone of the lapse rate-corrected inverse distance weighting. The solar irradiance scheme calculates the direct, diffuse, and reflected components of short-wave radiation over sloping surfaces based on the sun-slope geometry and compares the sum with that over a reference surface. The deviation from reference radiation is used to calculate the temperature correction term by an empirical conversion formula between the solar energy and the air temperature at an hourly time scale, which can be prepared seasonally for each land cover type. When this model was applied to a topographically complex area, the estimated temperature differences agreed much better with the observations than those by the conventional lapse rate correction method.