The Development of Composite Temperature Records

Traditionally, methods used in the creation of composite temperature records have depended, implicitly or explicitly, on the assumption that the difference in temperature between two nearby sites will be a constant for any day in a given month of the year. It is demonstrated that this assumption is not necessarily valid, particularly where the sites used in the creation of a composite record differ in local topography. Two techniques are proposed to relate daily maximum and minimum temperatures at two sites during a period of overlapping records to overcome this difficulty. It is demonstrated using data from Inverell, Australia, where the difference in daily minimum temperature between two sites is significantly dependent on the temperature at one of the sites, that these techniques substantially improve the accuracy of the simulation of daily minima at one site using records from the other. The best choice of technique depends on whether the highest priority is to simulate the overall temperature record or the frequency and nature of extreme events.