\documentclass[11pt]{article} \begin{document} \title{{Monte Carlo Filtering Algorithm for Nonlinear Stochastic Environmental Model} \\ {\em (Abstract)}} \author{ V. P. Jilkov and Tz. A. Semerdjiev \\ Laboratory for Parallel and Distributed Processing \\ Bulgarian Academy of Sciences \\ tel: (+3592) 731 498, fax: (+3592) 707 273, e-mail: signal@acad.bg} \maketitle \thispagestyle{empty} The work presents development and evaluation of an alternative Monte Carlo simulation filtering algorithm for application to environmental (atmoshperic, ocean etc.) data assimilation. Most of existing and proposed data assimilation schemes are designed on the assumptions that the estimate is the mean of Gaussian distribution and near-linearity of process dynamics, which do not match real processes adequately. Few nonlinear data assimilation algorithms are known, which are based on the classical nonlinear filtering theory, but their implementation is hampered by many restrictions and practical difficulties. A recently developed approach to nonlinear/non-Gaussian state estimation - the {\em bootstrap filtering} is adopted and applied in our work. A bootstrap data assimilation algorithm is designed and applied to the stochastically forced {\em double-well model}. The algorithm implements recursive Bayesian filtering and does not require the limiting assumptions and solving of the Fokker-Planck stochastic differential equations. By means of Monte Carlo simulation experiments, the performance of the proposed algorithm is evaluated and compared with known algorithms - Extended Kalman filter and Fokker-Planck equation based algorithm. \end{document}