System Architecture
===================

Core Components
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1. **State Vector Management**
   - Efficient handling of model states
   - Support for multiple state representations
   - Memory-efficient operations

2. **Observation Processing**
   - Flexible observation operator framework
   - Quality control mechanisms
   - Observation error handling

3. **Error Covariance Modeling**
   - Background error covariance representations
   - Observation error covariance handling
   - Localization implementations

4. **Assimilation Algorithms**
   - Variational methods (3D-Var, 4D-Var)
   - Ensemble methods (EnKF variants)
   - Hybrid approaches

5. **Numerical Optimization**
   - Cost function implementations
   - Gradient calculations
   - Minimization algorithms

Integration Layer
-----------------
- Model coupling interfaces
- I/O handling
- Parallel computation management
- Resource allocation