Measurement of True Mean Temperature for Determination of Climatic Trends
Howard B. Edwards · Journal of applied meteorology · 1982
It has been demonstrated that the methods used to measure daily mean temperatures are subject to bias errors and therefore, may not be accurate enough to determine climatic trends. To eliminate bias errors, it is necessary to measure temperature continuously with readings recorded often enough to provide at least two data points for each cycle of the highest frequency fluctuation discernible in the transducer signal. This can be accomplished by a system having a transducer with a 7 min time constant, the signals from which are sampled every 30 s. The resulting data can be filtered to show smoothed daily cycles and then reduced to 12 points per day with the daily cycle eliminated. These points are true mean temperatures and can be used through succeeding filtering steps to smooth and eliminate annual and solar cycles and reveal climatic trends.