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LAND SURFACE TEMPERATURE RESPONSES TO THE LAND COVER DYNAMICS IN WESTERN GHATS
(PDF)
T V Ramachandra, Srijith A H and Bharath S
Energy and Wetlands Research Group,
Centre for Ecological Sciences,
Indian Institute of Science - 560012
4. Materials
4.1. DATA PRODUCTS:
The data acquired by MODIS sensor present in TERRA platform has been analysed on temporal scale. The data has been collected through NASA LP DAAC which is a web user interface with an online search, discovery and ordering tool. MODIS, has 2330 km wide swath with revisit time of 1-2 days. It has 36 discrete spectral bands of differing spatial resolution (250m, 500m and 1000m) ranging in wavelength from 0.4 to 14.4 mm. The MODIS data products have improved our understanding of global dynamics and processes occurring on lands, oceans, and in lower atmosphere (Ren et al., 2008) The data products used in this study are MOD13Q1 (Vegetation Indices Product) and MOD11C2 (Land Surface Temperature Product). The tiles covering the study area are h24v06, h24v07, h25v07 and h25v08 are depicted in Fig. 4.1. The data has been acquired in the April months of 2001, 2008, 2015 and 2016 due to low cloud cover in the study area.
4.1.1. MOD13Q1:
The MOD13Q1 product provides Vegetation Index (VI) value at a per pixel basis which is available on a 16-day period. It has a spatial resolution of 250 m. There are 2 primary vegetation layers i.e. NDVI and EVI. This study has been carried out using Enhanced Vegetation Index (EVI) which has improved sensitivity over high biomass regions. The product is 16-bit signed data and the valid range is from -2000 to 10000. The EVI value from the satellite image has been obtained by using scaling factor 0.0001 (Huete et. al., 1999) as described in the metadata of the data product. The valid range of EVI is from -1 to +1.
4.1.2 MOD11C2:
The MOD11C2 product provides land surface temperature (LST) and emissivity values at per pixel. This product is configured on a 0.05-degree latitude/longitude climate modelling grid (CMG). It is available on an 8-day period at a spatial resolution of 1km. The data has been resampled to 250m for this study.The product is 16-bit unsigned data and the value ranges from 7500 to 65535. A scaling factor of 0.02 (Wan et. al., 2007) is used to convert the reflectance value into temperature in Kelvin which has been further converted to degree Celsius.
Temperature (°C) = (Pixel Reflectance Value * 0.02) – 273.16
4.1.3 GROUND DATA:
The ground truth data for different land use classes i.e. forest, plantation, water-body, settlements, agricultural farms etc. collected have been used during analysis and validation. Google Earth data are also used for exploratory data analysis, validation and supervision of LU in the study area.
4.1.4. NASA CLIMATOLOGY RESOURCE:
Global air temperature at 2 m from ground in 1° latitude and 1° longitude based on Climate Modelling Grid has been used for validation of LST maps. This data has been prepared using data acquired from different sensors and is available on a long term time series from 1983.
4.2. SOFTWARE TOOLS:
The whole study has been carried out using free and open source software: GRASS GIS and Q GIS.
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