气候变化领域集成服务门户

Increase in land surface temperature (LST) of growing urban areas in the current global warming scenario is a cause of concern for city planners. This study discusses the impact of land-use/land-cover (LULC) change on LST of the area in and around Rajarhat block, North 24-Parganas District, West Bengal, covering an area of 165km(2). Multi-spectral and multi-temporal satellite data from Landsat 5 TM (1990), Landsat 8 OLI (2016) and Sentinel 2A (2016) are used for the LULC mapping, and thermal infrared data from Landsat 5 TM and Landsat 8 TIRS (2016) are used for estimating the LST of 1990 and 2016. Results show that land-use pattern in November has changed in Rajarhat from 1990 to 2016: 13km(2) of vegetation cover lost due to urbanization; 9.3km(2) of open land converted to agricultural land and open fields/parks; 1.4km(2) of aquaculture ponds converted to tree cover/scrublands and 1.45km(2) of lakes/ponds filled up. Loss of vegetation (scrubland and tree) cover resulted in LST rise by about 1.5 degrees C. Aquaculture ponds have the ability to resist the rise in LST since the increase in temperature of this class is only 0.24 degrees C due to increase in its area. This change in land-use pattern over 26years has increased the LST by 0.94 degrees C. The urban-heat-island (UHI) phenomenon has also increased. The area of the strongest' heat-island phenomenon, as per UTVFI classification scheme, has increased by 20.1km(2). Positive correlation is observed between NDBI and LST's of urban areas (r=0.002 for 1990 and r=0.047 for 2016) which suggests that urbanization is responsible for the rise in LST. The NCEP NOAA surface temperature model suggests that the long-term trends in the rise in maximum LST over Rajarhat is about 1 degrees C from January 1990 to November 2016 with 90% confidence level validating the extracted LST data from satellites. Sustainable urban planning is required to arrest the rise in LST which includes urban forestry, construction of water bodies and fountains, preserving existing aquaculture ponds and reducing construction activities.