Assessing the Influence of Coastal Salt Pans on Land Surface Temperature: A Google Earth Engine-Based Study

Land surface temperature (LST) provides critical insight into the thermal behaviour of different land cover types, especially in sensitive coastal landscapes. In India, salt fields in the Thoothukudi district of Tamil Nadu State, covering about 101 km², contribute a major share in the total salt output of the country. This study assessed the influence of coastal salt pans on LST dynamics in Thoothukudi district using multi-temporal Landsat 8 data of the 2019-2023 period within Google Earth Engine (GEE). Unlike the earlier studies dealing with LST dynamics in urban or agricultural landscapes, this study quantifies the distinct thermal behaviour of active salt-production land and the surrounding vegetation. Differences in the LST dynamics were comparatively evaluated in different land cover types, i.e., sand, vegetation zones near and away from salt pans, built-up land and salt pans. This study uniquely contributes by introducing a comparative LST evaluation in two vegetation covers, one in close proximity to salt pans and another away from them. The results revealed the effect of a localized microclimate, which is not documented in the earlier studies. The Normalized difference vegetation index (NDVI), surface emissivity, and thermal band (Band 10) of Landsat 8 were used to determine LST. The results showed that the mean LST values of 27.11°C in sand, 26.95°C in built-up areas, 25.78°C in salt pans and 24.54°C in distant vegetation cover in the order of sand > built-up areas > salt pans > vegetation cover (near salt pans) > vegetation cover (away from salt pans). Further, the vegetation covers close to salt pans and built-up areas had comparatively higher LST values due to the influence of surrounding salt pans and built-up areas. Also, the LST of sand was almost comparable to that of salt pans. Findings of this study are useful to policymakers in planning appropriate strategies for land management and to overcome the impact of LST in future.