Time of observation and estimation of daily solar radiation for the Northern Great Plains

For various crop-climate and weather models, daily solar radiation records are an important input. Currently, daily solar radiation data for the northern Great Plains is available through an Automated Weather Data Network (AWDN). This network is a collaborative effort between the state climate offices of the region and High Plains Regional Climate Center (HPCC). However, availability of historical records of solar radiation is limited. This unavailability of long-term solar radiation records is a constraint for various climatological and climate impacts studies. To overcome this problem we are presenting solar radiation estimation methods based on historical records of daily maximum and minimum temperature, range between daily maximum and minimum temperature, and estimated daily clear sky solar radiation. Furthermore, observation time and its impacts on the accuracy of daily solar radiation estimation is also addressed. Results indicate that the methods estimate daily solar radiation more accurately for the northern and western portion of the northern Great Plains. In addition, daily solar radiation estimations based on mid-night observations are more reliable than estimates based on other observation times.