Modellering av reflektans från ett sockerbetsbestånd med hjälp av en strålningsmodell

Swedish. En Multispectral Canopy Reflectance Modell (MCRM) av Kuusk (1995) har använts för att simulera reflektansen i ett sockerbetsbestånd. De simulerade reflektansvärdena visade på hög absorbans i VIS-området, jämfört med mätningar i fält, och höga reflektansvärden i NIR-området. En "vårmodell" utfördes, och jämfördes med originalsimuleringen. Denna gav mer korrekta reflektansvärden.

English. The Multispectral Canopy Reflectance Model (MCRM) by Kuusk (1995) has been used to simulate the reflectance of a sugarbeet canopy. The simulated reflectance values show high absorptance in the VIS area, compared to field measurements, and high reflectance values in the NIR area. The errors may be due to overestimation of clorophyll content in the sugarbeet leaves and scattered light during field measurements. The estimation of the clorophyll content where carried out using the PROSPECT-model by Jacquemoud & Baret (1990). During the vegetation period, the state of the canopy moves towards a closed canopy, with sparse vegetation in spring. The MCRM-model was used to perform a “spring” simulation, which was compared to the original simulation. It accurately described the differences in reflectance between the dense and sparse canopies. The background, i.e. the soil, has larger influence on the canopy reflectance when the canopy is sparse, while the influence from LAI and clorophyll lessens. The sensitivity of the model changes with the canopy characteristics. In a closed or dense canopy, the leaves completely cover the ground and the sensitivity for leaf properties are high. The sensitivity patterns for a sparse canopy shows a larger sensitivity to soil properties and lesser sensitivity to leaf properties.