Surface thermal dynamics and air quality stressors in a rapidly urbanising semi-arid city: a multi-sensor satellite assessment of Greater Irbid, Jordan (2000–2025)

Background

Semi-arid cities of the Middle East face compounding pressures from rapid urban growth, rising temperatures and persistent air pollution, yet long-term evidence for secondary cities remains scarce.

Methods

This study examined twenty-five years of daytime surface thermal change and the present-day air quality regime of Greater Irbid, Jordan, using an integrated multi-sensor satellite framework. Land surface temperature (LST) was retrieved from Landsat 5, 8 and 9 Collection 2 Level-2 archives for six epochs between 2000 and 2025, and daytime surface thermal island intensity was computed against an elevation-controlled rural reference derived from epoch-matched Global Human Settlement Layer (GHSL) built-up surfaces. Five air quality stressors, namely nitrogen dioxide (NO2), sulphur dioxide (SO2), carbon monoxide (CO), formaldehyde (HCHO) and the ultraviolet aerosol index (AI), together with two contextual variables, ozone (O3) and methane (CH4), were characterised from Sentinel-5P TROPOspheric Monitoring Instrument (TROPOMI) records for 2019–2025.

Results

The city exhibited a daytime surface urban cool island typical of drylands that weakened from − 6.26 °C to − 4.14 °C between the study endpoints, though the contrast was not monotonic across the intervening epochs. This weakening was strongly associated with the 2.2-fold growth of the dense urban core (r = 0.977, 95 per cent confidence interval 0.80–1.00) and is consistent with densification-driven relative warming. NO2 peaked over the urban core with a winter to summer ratio of 1.93, HCHO and aerosols peaked in summer and CH4 tracked the global background rise, confirming retrieval consistency.

Conclusion

The results identify an east–south belt where elevated surface heat visually corresponds with pollution enhancements and provide a reproducible evidence base for cooling, greening and emission management in dryland municipalities.