Study Using a Diagnostic Satellite Based Model (VPRM) to Improve the Estimations of Atmosphere - Terrestrial Biosphere CO2 Exchanges Over India.

Planning of proper emission reduction policies and their successful implementation require accurate carbon budgeting at a regional level. Our study aims to quantify sources and sinks of carbon dioxide over Indian domain to the best fidelity using inverse modelling techniques. In order to better represent and quantify the atmosphere-biosphere CO2 exchange fluxes and ecosystem behaviour in the inverse modeling framework, the Vegetation Photosynthesis and Respiration Model (VPRM) is employed in our modelling system over Indian region. VPRM is a satellite based assimilation scheme with simple model structure, so as to facilitate successive optimization of parameters in the inverse modelling framework. As an initial step, we evaluated the VPRM model with eddy covariance observations over India from two different vegetation types (Betul; Deciduous forest and Sundarbans; Evergreen forest) for the year 2017. The comparison reveals that the model needs further refinement in parametrization even though the VPRM showed better performance than other existing terrestrial biosphere models (e.g ., TRENDY and Carbon Tracker (CT)) over Indian domain. Further analysis based on the Soil Moisture (SM) data shows a significant correlation between SM and ecosystem respiration. By establishing this relationship, we refine the ecosystem respiration estimation in VPRM. We also attempt to utilize satellite based Solar Induced Fluorescence (SIF) as a proxy to estimate Gross Primary Productivity (GPP) together with VPRM for the better representation of biospheric fluxes over India. Preliminary results will be presented and discussed.