• K Mallick

      Articles written in Journal of Earth System Science

    • Computation of regional gravity anomaly — A novel approach

      K Mallick K K Sharma

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      A new scheme is put forward based on the shape function concept of finite element approximation to compute regional gravity anomaly. The uniqueness of this approach is that excepting eight (or twelve) discrete gravity measurements coinciding with the eight (or twelve) nodes of a quadratic (or cubic) isoparametric element superimposing the map space, often very large, no other observed gravity data are invoked to compute the regional. Tests on two Bouguer gravity fields, an oil prospect and a rift valley confirmed better resolution by this approach. This technique is straight forward, uses simple mathematics to be easily automated and yields repeatable results.

    • Finite element concept to derive isostatic residual maps — Application to gorda plate and Sierra Nevada regions

      K Mallick K K Sharma

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      A new space-domain operator based on the shape function concept of finite element analysis has been developed to derive the residual maps of the Gorda Plate of western United States. The technique does not require explicit assumptions on isostatic models. Besides delineating the Gorda Plate boundary, the residual maps exhibit a close match both in their anomaly patterns and magnitudes with previously computed residual maps based on the theory of isostasy.

    • Development of regional wheat VI-LAI models using Resourcesat-1 AWiFS data

      Sasmita Chaurasia R Nigam B K Bhattacharya V N Sridhar K Mallick S P Vyas N K Patel J Mukherjee Chander Shekhar Dhiraj Kumar K R P Singh G D Bairagi N L Purohit J S Parihar

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      The time of forcing of spatial LAI to crop models at single or multiple stages is important to simulate crop biomass and yield in varying agro-climatic conditions and scales. The high temporal resolution (5-day) by Advanced Wide Field Sensor (AWiFS) on-board Resourcesat-1 Satellite IRS-P6 with 56 m spatial resolution and large swath (740 km) has substantially increased the availability of regional clear sky optical remote sensing data. The present study aimed at developing empirical vegetation index VI-LAI models for wheat using AWiFS optical data in four bands and in-situ measurements sampled over five different agro-climatic regions (ACRs) during 2005–2006 followed by validation during 2006–2007. While nonlinear relations exist for all the three normalized indices such as normalized difference vegetation index (NDVI), normalized difference water index (NDWI) and Green NDVI, linear relation was the best fit for ratio vegetation index (RVI). Both NDVI and RVI models generally showed better correlation ranges (0.65–0.84 for NDVI and 0.37–0.76 for RVI) than other indices. The common NDVI-LAI model was found to produce lower root mean square errors (RMSE) between 0.5 and 1.1 from pooled model than those between 0.5 and 1.32 from regional models. The rate of substantial increase in errors from NDVILAI model (RMSE of modelled LAI: 0.85 to 1.28) as compared to RVI-LAI model (RMSE of modeled LAI: 1.12 to 1.17) at LAI greater than 3, than below 3 revealed the early saturation of NDVI than RVI. It is therefore recommended that LAI estimates can be used to force crop simulation model up to early vegetative stage based on NDVI and maximum vegetative to reproductive stages based on RVI.

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