Application of collected data
Presentations at the DBCP Technical Workshop
Buenos Aires, Argentina, 17-18 October 2005


Theme 2: Operational enhancements and practices

12. A Simple Model for Drifting Buoy Life-Times, and a Method for Estimating Evolution of a Network's Size

Authors: Etienne Charpentier, Mathieu Belbéoch, Julien Bourcier

Abstract: Using JCOMMOPS database, and series of actual drifter life-times, it was shown that survivability of a drifting buoy network fits very well with an exponential model N(t)=N₀ e^-αt. Using regression method, α coefficient can be estimated. This coefficient is directly linked to the theoretical network half life L_1/2: α=ln(2)/L_1/2. Assuming a constant deployment rate of R_x drifters per day, it is therefore possible to estimate evolution with time of the size of a network of consistent buoys: N(t)= (N₀ - R_x/ α) e^-αt+R_x/ α. Network size will eventually tend towards theoretical limit of R_x/ α buoys. In order to maintain a buoy network at a target level of N_t units, it is therefore recommended to deploy buoys at a rate of N_t α units per day. A higher deployment rate will be needed in case the initial number of buoys is substantially lower than the target. New JCOMMOPS web page permits to query the database in order to make quick estimation of α coefficient and to simulate network evolution based on provided criteria. This works, of course provided that buoy deployment information, and particularly deployment date is made available to JCOMMOPS. Recently developed buoy metadata collection system and deployment notification scheme permits to collect required information and to assist buoy operators in managing their networks.