WRF ARW User's Guide - MMM - UCAR

Banana Scheme
OBSGRID
In analyses of wind and relative humidity at pressure levels, the circles from the standard
Cressman scheme are elongated in the direction of the flow and curved along the streamlines.
The result is a banana shape. This scheme reduces to the Ellipse scheme under straight-flow
conditions, and the standard Cressman scheme under low-wind conditions.
Multiquadric scheme
The Multiquadric scheme uses hyperboloid radial basis functions to perform the objective
analysis. Details of the multiquadric technique may be found in Nuss and Titley, 1994: "Use of
multiquadric interpolation for meteorological objective analysis." Mon . Wea . Rev ., 122, 1611-
1631. Use this scheme with caution, as it can produce some odd results in areas where only a few
observations are available.
Quality Control for Observations
A critical component of OBSGRID is the screening for bad observations. Many of these QC
checks are optional in OBSGRID.
Quality Control on Individual Reports
• Gross Error Checks (sane values, pressure decreases with height, etc.)
• Remove spikes from temperature and wind profiles.
• Adjust temperature profiles to remove superadiabatic layers.
• No comparisons to other reports or to the first-guess field.
The ERRMAX test
The ERRMAX quality-control check is optional, but highly recommended.
• Limited user control over data removal. The user may set thresholds, which vary the
tolerance of the error check.
WRF-ARW V3: User’s Guide 7-5