The diagonal observation error covariance R implementation in OOPS can be used both for any of the toy models <../toy-models/index>
, and for the models that use UFO <../../ufo/index>
.
Observation error standard deviations for R are read as an ObsError
group from the observation file.
The covariance can be configured using the following options:
random amplitude
(optional, default value is 1.0) -- a multiplier used when generating a random sample from the observation error covariances (standard error deviations are multiplied by this number)zero-mean perturbations
: logical variable with a default offalse
. Set totrue
to constrain observation perturbations to have a zero ensemble mean (can be used in theEnsemble of Data Assimilations (EDA) <../applications/ensemble-applications>
). If this option is set totrue
, the following options also have to be set:member
: ensemble member index (1-based);number of members
: number of ensemble members.
Important
For the zero-mean perturbations option to work, the following requirements must be satisfied:
- The
obs perturbations seed
option in theobs space
section must be set to the same value for all ensemble members. - All ensemble members must use the same observations in the same order.
A diagonal R can be configured as:
obs error:
covariance model: diagonal
For an EDA experiment with 10 ensemble members, and perturbing observations ensuring zero-mean perturbations, a diagonal R for the 2nd ensemble member can be set up as:
obs error:
covariance model: diagonal
zero-mean perturbations: true
member: 2
number of members: 10