Temperature-Humidity Index described by fractal Higuchi Dimension affects tourism activity in the urban environment of Focşani City (Romania)

The bioclimatic analysis in the context of urban environment and tourism activity is relatively new in Romania and highly important for the development of tourism. In the present study, the evidence of increasing air temperature by the Temperature-Humidity Index (THI) was conducted in the Focşani City, Romania, within the period of 17 years (2001–2017). Bioclimatic conditions were defined for this area by the relationship between air temperature, relative humidity, and THI. Tourism activities, such as nights spent in the city and arrivals of tourists in accommodations, were associated with the THI for the periods 2001–2016. As the THI values increased, higher tourist activity was recorded as measured by the overnight stays and arrivals in accommodations. The results of the bioclimatological analysis further revealed a high discomfort by the low winter temperatures and the high summer heat. The highest THI value, recorded in this period, was 38.5 °C in August 2017, while the lowest was − 6.8 °C, in January 2013. The bioclimatic comfort positively correlated with an increase in the number of arrivals and nights spent, in summer and in early autumn. In this paper, the analysis of THI in Focşani City (Romania) was used as a research example, to show that analysis of extreme temperatures can improve the future characterization of climatic events, its variability, and spatial pattern. Higuchi Dimension (D_H) was used for additional assessment of THI, in order to better define its annual and monthly THI complexity. The innovative results consist of using the D_H to determine the degree of complexity of THI oscillations and their impact on tourism activity. This study reports tools that efficiently define periods when conditions are usually unfavorable for tourism. This information facilitates the decision to increase the tourist offer for this period and thus may help decision-makers in the management of regional tourism. This can be the basis for future studies on the prevention of negative effects caused by the extreme weather conditions.