Climate reference stations in Germany: Status, parallel measurements and homogeneity of temperature time series

Abstract. Germany's national meteorological service (Deutscher Wetterdienst, DWD) operates a network of so-called "climate reference stations". These stations fulfill several tasks: At these locations observations have already been performed since several decades. Observations will continuously be performed at the traditional observing times, so that the existing time series are consistently prolonged. Currently, one specific task is the performance of parallel measurements in order to allow the comparison of manual and automatic observations. These parallel measurements will be continued at a subset of these stations until at least 2018. Later, all stations will be operated as automatic stations but will also be used for the comparison of subsequent sensor technologies. New instrumentation will be operated in parallel to the previously used sensor types over sufficiently long periods to allow an assessment of the effect of such changes. Here, we present the current status and an analysis of parallel measurements of temperature at 2 m height. The analysis shows that the automation of stations did not cause an artificial increase in the series of daily mean temperature. Depending on the screen type, a bias with a seasonal cycle occurs for maximum temperature, with larger differences in summer. The effect can be avoided by optimizing the position of the sensor within the screen.