• D B Shah

      Articles written in Journal of Earth System Science

    • Simulation of at-sensor radiance over land for proposed thermal channels of Imager payload onboard INSAT-3D satellite using MODTRAN model

      M R Pandya D B Shah H J Trivedi S Panigrahy

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      INSAT-3D is the new generation Indian satellite designed for improved Earth observations through two payloads – Imager and Sounder. Study was conducted with an aim of simulating satellite level signal over land in the infrared channels of the Imager payload using a radiative transfer model MODTRAN. Satellite level at-sensor radiance corresponding to all four infrared channels of INSAT-3D Imager payload is obtained using MODTRAN and sensitivity of at-sensor radiance was inferred as a function of input parameters namely, surface temperature, emissivity, view angle and atmospheric water vapour, which is helpful in understanding the signal simulation scheme needed for retrieving a very critical parameter namely, land surface temperature.

    • Estimating minimum and maximum air temperature using MODIS data over Indo-Gangetic Plain

      D B Shah M R Pandya H J Trivedi A R Jani

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      Spatially distributed air temperature data are required for climatological, hydrological and environmental studies. However, high spatial distribution patterns of air temperature are not available from meteorological stations due to its sparse network. The objective of this study was to estimate high spatial resolution minimum air temperature (𝑇_{min}) and maximum air temperature (𝑇_{max}) over the Indo-Gangetic Plain using Moderate Resolution Imaging Spectroradiometer (MODIS) data and India Meteorological Department (IMD) ground station data. 𝑇_{min} was estimated by establishing an empirical relationship between IMD 𝑇_{min} and night-time MODIS Land Surface Temperature (𝑇_{s}). While, 𝑇_{max} was estimated using the Temperature-Vegetation Index (TVX) approach. The TVX approach is based on the linear relationship between 𝑇_{s} and Normalized Difference Vegetation Index (NDVI) data where 𝑇_{max} is estimated by extrapolating the NDVI-𝑇_{s} regression line to maximum value of NDVImax for effective full vegetation cover. The present study also proposed a methodology to estimate NDVImax using IMD measured 𝑇_{max} for the Indo-Gangetic Plain. Comparison of MODIS estimated 𝑇min with IMD measured 𝑇min showed mean absolute error (MAE) of 1.73°C and a root mean square error (RMSE) of 2.2°C. Analysis in the study for 𝑇_{max} estimation showed that calibrated NDVImax performed well, with the MAE of 1.79°C and RMSE of 2.16°C.

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