Observation error covariances in UFO

UFO contains several observation error covariance operators (R-matrix operators):

• Observation error covariance with cross-variable (cross-channel) correlations
• Diagonal observation error covariance
• Correlated Observation Error Covariance with Diffusion
• Observation error covariance with correlations for observations within one record

Specifying observation error standard deviations

For all of the supported observation error covariance matrices, observation error standard deviations are read from the ObsError group of the observation file. Observation filters can change those values, and inflate or assign observation error standard deviations using Filter Actions.