Analysis of Diurnal Air Temperature Trends and Pattern Similarities in Highland and Lowland Stations of Italy and UK

TL;DR

This study analyzes hourly air temperature trends across UK and Italian highland and lowland stations from 2002 to 2021, revealing significant seasonal warming patterns and trend similarities within groups using advanced statistical and clustering methods.

Contribution

It introduces a comprehensive analysis of diurnal temperature trends across different regions and altitudes using hierarchical clustering and correlation techniques, highlighting regional climate change patterns.

Findings

Significant warming trends in Italian stations during February, July, August, and December.

Pattern similarities within station groups, especially in certain months.

No significant overall trends in UK highland stations.

Abstract

In this paper, an analysis of hourly air temperatures in four groups of 32 stations of the UK highland (five stations), UK lowland (four stations), Italian highland (eleven stations), and Italian lowland (twelve stations) at various altitudes was conducted over the period from 2002 to 2021. The study aimed to examine the trends of each hour of the day in that period, over different averaging time windows (-10 day, -30 day, and -60 day). The trends were computed using the Mann-Kendall trend test and Sen's slope estimator. The similarity of trends within and across the groups of stations was assessed using the hierarchical clustering with dynamic time warping technique. An additional analysis was conducted to show the correlation of trends among the group of stations using the correlation distance matrix. Hierarchical clustering and distance correlation analysis show trend similarities and correlations, also indicating dissimilarities among different groups. Using 30 day averages, significant warming trends in specific months at the Italian stations are evident, especially in February, July, August, and December. The UK highland stations did not show statistically significant trends, but clear pattern similarities were found within the groups, especially in certain months. The ultimate goal of this paper is to provide insights into temperature dynamics and climate change characteristics on regional and diurnal scales.