Homogenization of the global historical database (HCLIM)

Homogenization of the global historical database (HCLIM)

Instrumental meteorological observations are crucial for the analysis of climate backwards in time to reconstruct climate variations. However, the collection of instrumental data dating back to 1658 allows many of the long climate series to have often been affected by inhomogeneities (artificial shifts) due to changes in measurement conditions (relocations, instrumentation, change in environment, etc.). To deal with this problem, modern homogenization procedures have been used and developed to detect and adjust inhomogeneities. Homogenization in climate research means the removal of non-climatic changes. This presentation describes the homogenization of the early instrumental dataset (HCLIM; https://doi.pangaea.de/10.1594/PANGAEA.940724) of monthly mean temperature time series. New homogenization algorithm validation methodology is assessed here on early instrumental data, and its use to assess the skill of three different algorithms, when applied to early instrumental data. The methods tested were PHA, BART and CLIMATOL. Results and challenges of using these methods on early instrumental data will be shown. From the database that has been created (published January 2023), it has been necessary to clean up the data and at the same time use the data to see what strengths and weaknesses exist with the database. The clean-up has consisted of changing the data format for use for homogenisation, and testing latitude, longitude and meters above sea level and the possibility of obtaining verified data for comparison. You can also see that there is some data that cannot be used for this purpose. Something can be used for completely different purposes, e.g., finding extremes. It has also been a learning process to use these homogenization programs.