Homogenization of daily temperature data
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Date
2025-06-20
Authors
Θεοχαράτου, Αναστασία
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Abstract
Homogenization of meteorological time series refers to the process of detecting and removing non-climatic effects from the data so that any fluctuations can be attributed solely to climatic factors. Conversely, inhomogeneous time series contain variations unrelated to climate change but instead arise from other factors, such as changes in measurement methodology or instrumentation. The homogenization process consists of two stages: (i) detecting discontinuities in the time series and (ii) applying corrections to eliminate these discontinuities.
Inhomogeneities can be identified either directly through graphical representation of the time series or indirectly through metadata analyses and statistical tests, which include information about the station, measurement instruments, and observation methods.
In this study, we will utilize the MASH method (MASH v3.03) to identify the inhomogeneities. This method was developed by the Hungarian Meteorological Service for the homogenization of meteorological data. The MASH method depends on the meteorological parameter being homogenized and can be implemented with various statistical models. For the homogenization of daily values, there are two options: either using the inhomogeneities already identified in monthly values or applying a direct method to the daily values, although the latter is considered less stable due to greater variability.
The basic steps of the MASH method include:
• Creation of monthly series from daily ones.
• Filling in the missing values with the help of coefficients from neighboring stations.
• Identification of inhomogeneities in the monthly values.
• Evaluation of the results.
• Correction of the daily values according to the monthly anomalies.
The process is completed by evaluating the results and, if necessary, repeating some steps.
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Keywords
Homogenization, Mean daily temperature, CLIMATOL