Sasaki's Pathway to Deterministic Data Assimilation -- Data Assimilation for Numerical Weather Prediction: A Review -- Theoretical and Practical Issues of Ensemble Data Assimilation in Weather and Climate -- Information Measures in Ensemble Data Assimilation -- Real Challenge of Data Assimilation for Tornadogenesis -- Radar Rainfall Estimates for Hydrologic and Landslide Modeling -- High-Resolution QPE System for Taiwan -- Assimilation of Satellite Data in Improving Numerical Simulation of Tropical Cyclones: Progress, Challenge and Development -- Diagnostics for Evaluating the Impact of Satellite Observations -- Impact of the CHAMP Occultation Data on the Rainfall Forecast -- Parameter Estimation Using the Genetic Algorithm in Terms of Quantitative Precipitation Forecast -- Applications of Conditional Nonlinear Optimal Perturbations to Ensemble Prediction and Adaptive Observation -- Study on Adjoint-Based Targeted Observation of Mesoscale Low on Meiyu Front -- Ocean Data Assimilation: A Coastal Application -- Comparison of Ensemble-Based Filters for a Simple Model of Ocean Thermohaline Circulation -- Preconditioning Representer-based Variational Data Assimilation Systems: Application to NAVDAS-AR -- Cycling the Representer Method with Nonlinear Models -- Implementation of the Ensemble Kalman Filter into a Northwest Pacific Ocean Circulation Model -- Particle Filtering in Data Assimilation and Its Application to Estimation of Boundary Condition of Tsunami Simulation Model -- Data Assimilation in Hydrology: Variational Approach -- Recent Advances in Land Data Assimilation at the NASA Global Modeling and Assimilation Office -- Assimilation of Soil Moisture and Temperature Data into Land Surface Models: A Survey -- Assimilation of a Satellite-Based SoilMoisture Product into a Two-Layer Water Balance Model for a Global Crop Production Decision Support System. This book presents the most recent achievements in data assimilation in Geosciences, especially in regards to meteorology, oceanography and hydrology. It spans both theoretical and applied aspects with various methodologies including variational, Kalman filter, maximum likelihood ensemble filter and other ensemble methods. Besides data assimilation, other important topics are also covered including targeting observation, parameter estimation, and remote sensing data retrieval. The book will be useful to individual researchers as well as graduate students as a reference in the field of data assimilation.