Recent studies intensely discuss the apparent green-up behaviour of Amazon rain forests during dry seasons. One explanation was that the forests were adapted to droughts through deep roots and profit from increased irradiance during the dry season. Another stream of studies found high impact of solar geometry on the often used MODIS Enhanced Vegetation Index (EVI) and calls for paying attention to this effect. One study completely challenges the green-up hypothesis and attributes all seasonal variation to effects of solar geometry. So far no final answer for this debate has been found.
One part in the puzzle is to assess the sensitivity of EVI to solar geometry. This has been done with observational data in different studies. However, vegetation radiative transfer models (RTM) like PROSAIL have not been exploited for this purpose yet. These models allow to study the solar and viewing geometry effect in a universal way while excluding atmospheric noise like clouds and aerosols. Additionally, they can be expanded to other vegetation indices and sensor band definitions. This is also relevant in respect to the upcoming Sentinel-3 mission as well as other wide swath sensors.
In this study the Automated Radiative Transfer Models Operator (ARTMO) software package will be exploited. ARTMO offers a single interface to several RTMs with a MATLAB graphical user interface (GUI) environment.
- Find possible model parametrisations
- Define a set of relevant VIs
- Study sensitivity of VIs to viewing and solar geometry with the ARTMO toolbox
- Investigate mixed effects between changing geometry and other VRTM parameters
- GRS-32306 – Advanced Earth Observation
- Affinity with scripting (e.g. MatLab, R) is a preference