New variables for OABSFC:
DTAAREA Area of objective analysis if not same as grid file GUESS First guess file, if available GUESFUN First guess field, if available QCNTL Quality control threshold for first guess GAMMA Value of the convergence parameter SEARCH Search radius for stations NPASS Number of passes in the Barnes Scheme OABND Bounds file(s) to use for 'blocking' out regions
DTAAREA is typically the same area as the grid file, and may be left blank or set to DATA. Stations which posses bad data may be eliminated from consideration by appending a tag /-@station1;station2;etc. to this variable.
GUESS and GUESFUN can be used to supply the original guess field as a zeroeth pass of the Barnes analysis. GUESFUN may be different than the field to be analyzed. For example, the 10 meter temperature from a model at a specific forecast hour can be used as a first guess for the 2 meter temperature analyzed field. QCNTL can be used to create a threshold for rejecting data which deviate from the expected first guess field.
GAMMA is a value between 0 and 1. Typically a value between .2 and .3 is used.
SEARCH is a value between 1 and 50, such that stations receiving a weight less than EXP(-SEARCH) are considered negligible. Typically a value of 20 is used, which corresponds to a weight threshold of approximately 2e-9. A modifier of /EX may be used to allow data extrapolation for regions that lack at least 3 station within the search radius.
NPASS may be from 1 to 5 passes. 2 passes are recommended.
A word of warning! Although objective analysis does filter
data so that any singular value does not contribute solely to a grid point value,
it does not prevent the contribution of BAD bad data.
You should always inspect the raw data that is used in objective analysis to
determine possible contamination of grid results. When using gridded data,
the #1 rule is always, Garbage in, Garbage out.