Why find the state of the atmosphere?
- Initial conditions for prediction
- ... the atmosphere "is a chaotic system in which errors introduced into the system can grow with time ... As a consequence, data assimiltion is a struggle between chaotic destruction of knowledge and its restoration by new observations" (Leith, 1993)
- The "ultimate problem in meteorology" (Bjerknes, 1911)
- Climate analysis / reanalysis
- Model and observing system validation
- Observation system design