Chapter 3. Data Assimilation in Meteorology and Oceanography1. Introduction and Motivation; 2. Evolution of Data Assimilation in Meteorology; 3. Atmosphere and Ocean: Dynamics, Data Sets, and Models; 4. Estimation Theory and Data Assimilation; 5. Current Status of Meteorological Data Assimilation; 6. Current Status of Oceanographic Data Assimilation; 7. Concluding Remarks; References; Chapter 4. Diabatically Forced Mesoscale Circulations in the Atmosphere; 1. Introduction; 2. Free Oscillations; 3. Effects of Basic State Baroclinicity; 4. Effects of Horizontal Mean Flow Advection.