Assessment of the Basque Country Automatic Weather Station Network for Climate Monitoring: Quality Control, Homogenization and Site Classification

Reliable climate monitoring depends on observational networks that are not only long-term and high-quality, but also representative of local environmental conditions. In regions such as the Basque Country, the predominance of automatic weather stations (AWS) presents both an opportunity and a challenge for climate applications, as these networks are primarily designed for real-time weather monitoring rather than climate analysis.

This study presents a comprehensive framework to assess the suitability of the Basque Country AWS network for climate monitoring purposes. The network, operated by Euskalmet, consists of more than one hundred stations providing high-frequency observations, with many records extending over two decades. The methodology integrates multiple components to ensure data reliability and representativeness. A systematic network characterization is carried out, followed by an automated site classification based on World Meteorological Organization (WMO) guidelines. This classification incorporates geospatial information, including land use, digital elevation models, canopy height, and geomorphological analysis using geomorphons, complemented by in-situ inspections.

Climate time series of key variables such as temperature and precipitation are processed through advanced quality control and homogenization techniques, including the ACMANT method. Breakpoint detection is supported by metadata analysis to identify non-climatic influences such as instrumentation changes or station relocation. The representativeness of the AWS network is evaluated through comparisons with reference climatological datasets, allowing the identification of stations suitable for climate monitoring applications. To support operational use, a system of station fact sheets has been developed, integrating metadata, quality indicators, homogenization status, and spatial context for each station. These tools enhance traceability and facilitate the integration of AWS data into climate services.

The results demonstrate that, while AWS networks are not initially designed for climate monitoring, a significant subset of stations can provide valuable and consistent climate information when properly evaluated, processed, and contextualized within a robust methodological framework.