Effects of the summer season and religious holiday periods on tropospheric NO₂ levels in Türkiye’s coastal tourism destinations: A Sentinel-5P/TROPOMI and GIS-based analysis (2023–2025)

This study investigates tropospheric NO2 variations observed in the Mediterranean and Aegean regions—Türkiye’s prominent coastal tourism hubs—during the 2023–2025 period, within the context of seasonal summer intensity and short-term mobility during Eid al-Fitr (Ramadan Feast) and Eid al-Adha (Feast of Sacrifice). The study utilizes Sentinel-5P/TROPOMI tropospheric NO2 data to generate daily regional median values for selected coastal tourism districts. The analysis was structured around three primary comparisons: (i) the “adjusted” summer period, isolated from the impacts of Eid al-Adha, against a “reference period” encompassing the phases before and after the summer; (ii) the Eid al-Fitr analysis; and (iii) the Eid al-Adha analysis. The holiday-specific assessments were conducted to include seven-day temporal windows preceding and following the respective holiday periods. Statistical evaluations employed the Mann–Whitney U test for summer-reference comparisons, while the Kruskal–Wallis H test was used for groups spanning pre-holiday, holiday, and post-holiday periods. For significant overall results, Dunn’s post-hoc test was applied. Findings indicate that the “adjusted” summer period yielded higher NO2 levels than the reference period across both regions and all years, with these differences becoming statistically significant particularly in 2024 and 2025. In contrast, the holiday-window analyses did not reveal a consistent short-term effect for either Eid al-Fitr or Eid al-Adha; holiday-period elevations, most notably during Eid al-Fitr 2024 in the Mediterranean region, remained isolated and were not statistically robust. These results demonstrate that the dominant pattern of tropospheric NO2 variation in the studied coastal destinations is primarily associated with seasonal and tourism-driven intensity spanning the summer season, rather than short-term religious holiday periods.