Methodological Approach for the Characterisation and Trend Analysis of Subsidence Thermal Inversions: The Case of the Canary Islands

Abstract

The study of the troposphere's vertical structure has been performed in a variety of ways as technological advances have been implemented. In recent decades, data from thermodynamic soundings have been the main support for the analyses. However, the geographical discontinuity of these records and the existence of relatively short series in many of the measurement points make it advisable to establish methods of analysis with greater spatial and temporal coverage. This work proposes a methodology based on the atmospheric reanalysis of ERA5, with an analysis period of 84 years (1940–2023). Its application to the specific case of the Canary Islands offers solid results consistent with the work published to date. Thus, all the parameters that define the subsidence thermal inversions (STIs), which separate a lower, cool and humid air mass from an upper, warm and dry one in the region, are characterised. Among the trends identified, an increase in the number of inversions and a marked decrease in their altitude—100 m above sea level—stand out in the series analysed, with a significant warming above the inversions and greater atmospheric stability in the region. As a consequence of these changes, significant environmental repercussions are foreseeable, especially in various agricultural and biogeographical aspects.