Crop Yield Estimation from Simulated Carbon Flux using SCOPE: A Case Study of Samrakalwana Village In India
Creators: name: De, Ranit
Publisher: name: Master's thesis, University of Twente
Year: 2021
Subjects: Gross Primary Production
Evapotranspiration
Crop yield estimate
Remote sensing
Radiative transfer models
India
SCOPE
Sentinel-3
Sentinel-2

description: The world has been facing a huge population boom for the last few decades. In this context, food security is a big challenge for many developing countries. Crop yield estimates play a crucial role in formulating food-related policies. They are generally produced using statistical data. But integrating actual remote sensing observations and deeper understanding of the dynamics of crops can help us to provide more accurate crop yield estimates. Moreover, we can have a sense of how crops respond to changing climatic conditions.

Several parameters (such as chlorophyll content, leaf area index [LAI], water content in leaf etc.) defining crop dynamics are essential inputs for modelling ecosystem carbon and water fluxes. It is possible to retrieve values of these parameters from remote sensing observations. This study focuses on two wheat-growing seasons (2018-19 and 2019-20) at Samrakalwana village, located in the northern part of India. The main objective of this study is to simulate ecosystem fluxes using Soil Canopy Observation of Photosynthesis and Energy fluxes (SCOPE) with vegetation parameters retrieved from Sentinel-3 (S3) and Sentinel-2 (S2) data. Then, the simulated carbon flux was used to provide crop yield estimate.

Two radiative transfer models (i.e., Optical Radiative Transfer Routine [RTMo] of SCOPE and Soil-Plant-Atmosphere Radiative Transfer [SPART]) were inverted to retrieve mainly crop parameters from S3 Ocean and Land Color Imager (OLCI) and S2 Multispectral Instrument (MSI) observations. The RTMo in SCOPE only represents a soil-vegetation system, whereas the SPART includes atmosphere also and it is possible to retrieve parameters defining atmospheric conditions (Aerosol Optical Thickness [AOT], columnar water and ozone content). The data from S3 OLCI was used as it has observations from 21 different bands with a higher temporal resolution of 1.1 days. In contrast, the advantage of S2 MSI is its higher spatial resolutions (4, 6 and 3 bands with 10m, 20m and 60m resolution respectively).

The retrieved parameters and meteorological data fromECMWFERA5 datasetwere then used to model ecosystem fluxes (Gross Primary Production [GPP] and Evapotranspiration [ET]) using SCOPE. The SCOPE simulated GPP and ET were compared against MODIS and ECOSTRESS bases GPP and ET products. Then simulated GPP fluxes were used to provide crop yield estimate. Supplementary information, such as Water Use Efficiency (WUE), Light Use Efficiency (LUE) and Evaporative fraction (EF), were also calculated.

The retrieved parameters, in general, are affected by spikes due to noisy input data. In some cases, the expected pattern of crop dynamics can be observed and retrieved LAI agrees with field measured LAI. The SCOPE simulated GPP flux was in a range of 0 to 12 μmol m2s-1. The simulated ET was in a range of 0 to 11 mm day-1. It was found that the values of simulated fluxes are mostly higher than the MODIS based estimate. Crop yield estimates from simulated carbon fluxes were also bit higher than the actual field measurements.