Radiometric in-situ measurements (within the OCEANET project)
Anja Bernhardt, Dipl. Phys., PhD student
Supervisor: Prof. Dr. Astrid Bracher
Ocean Color satellite measurements provide an important tool to monitor climate relevant changes in the oceans on a global scale. Nevertheless, it is necessary to validate remote sensing measurements with ground-truth data. Especially in the open ocean such measurements are scarce. During several cruises in the Atlantic and Arctic Ocean a ground-based dataset was -and still is- collected covering a large area.
This study predominantly concentrates on radiometric measurements that were accomplished with hyperspectral TriOS RAMSES radiometers, both, in the water column and above the water surface.
Two different kinds of instruments are used to measure irradiance and radiance (see Figures). Both provide spectra between 350 and 950 nm with a spectral resolution of 3.3 nm.
Key objectives of the study are
1. Validation of MERIS, MODIS and SeaWiFS Level 2 products with ground based radiometric measurements
The remote sensing reflectance is calculated from radiometric measurements from both, above- and below-water data. Above- and below-water reflectance will be compared and immersion factors will be determined. Another aspect will be the comparison of RAMSES radiometers with other instruments that were deployed during the same cruise.
2. Modeling of Inherent Optical Properties (IOPs) from Apparent Optical Properties (AOPs) and comparison to other models
The goal of this objective is to obtain a model to retrieve IOPs from AOPs on the basis of the implemented biogeochemical and optical measurements. This model will be compared to other models and their outcomes will be interpreted. Additionally the ground-truth optical data will be used as input parameters for radiative transfer models like “Sciatran” and the obtained model might as well provide further input parameters.
Cooperation Partners:
- GKSS (R. Röttgers)
- IMARE, Hochschule Bremerhaven (O. Zielinski)
- OCEANET Project / IFM-GEOMAR (A. Macke, K. Bumke)
- PEBCAO Plankton Ecology and Biogeochemistry in a Changing Arctic (E. Noethig, I. Peeken, K. Metfies, A. Engel, B. Niehoff, C. Hamm)
- Scripps (D. Stramski)
