Radiative transfer modeling

A Monte Carlo code for ocean color simulations (MOX)  has been developed to model in-water radiometric fields of downward and upward irradiance (Ed and Eu), and upwelling radiance (Lu) in a two-dimensional domain with a high spatial resolution.

 

The efficiency of the code has been optimized by applying state-of-the-art computing solutions, while the accuracy of simulation results has been quantified through benchmark with the widely used Hydrolight code for various values of seawater inherent optical properties and different illumination conditions. The effects of sea-surface geometries on radiometric quantities have been investigated for different surface gravity waves. Data products from simulated radiometric profiles have finally been analyzed as a function of the deployment speed and sampling frequency of current freefall systems in view of providing recommendations to improve measurement protocols.

 

Results from this analysis indicate that the accuracy of data products from measurements performed with free-fall systems can be increased by capturing the variability induced by wave focusing and defocusing effects over the extrapolation layer. This objective can be efficiently pursued by reducing the deployment speed rather than by significantly increasing the sampling frequency. From a practical perspective, the reduction of the deployment speed should comply with limitations imposed by additional sources of uncertainty, such as in-water sensor tilt (a fast deployment contributes to a better vertical asset of the free-fall system) and changes in illumination conditions during profiling. As a guiding principle, the multicast measurement methodology is, hence, recommended as an alternative (or even in addition) to slow radiometer deployments.

 

Figure 1. Example of MOX simulation results showing light focusing effects induced by the sea-surface.

Figure 1. Example of MOX simulation results showing light focusing effects induced by the sea-surface.

 

 

Projects: 
Authors: 

Tamito Kajiyama

Tamito Kajiyama joined the Geo-Info project of the Center of Informatics and Information Technology, New University of Lisbon, in April 2008. His current research interest focuses on the design and implementation of a high-performance computing (HPC) solutions for Monte Carlo ocean color simulation.

Partners: 

Faculty of Science and Technology (FCT)

Faculdade de Ciências e Tecnologia (Faculty of Science and Technology; FCT) is one of the nine academic units of Universidade Nova de Lisboa (UNL). The FCT/UNL campus is located in Monte de Caparica and covers approximately 30 ha, with additional capacity expansion to 60 ha.  Founded in 1977, FCT/UNL is one of the most prestigious Portuguese public schools of science and engineering today, with a total enrolment of ca. 7500 students, of which nearly 1400 are postgraduate students (MSc and PhD).

Centre for Marine and Environmental Research (CIMA)

By nature, CIMA a multi­disciplinary unit that explores the connections between environments, processes and human populations using scientific methods coupled with state­of­the­art modelling techniques. Apart from research, CIMA places a strong emphasis on training and education, as well as providing consultation services, digital applications and scientific information to the scientific and public domains. CIMA activity is focused on 3 general aims: 1. scientific research; 2. training at Masters and PhD level and 3.