25.12.2012 Views

WRF ARW User's Guide - MMM - UCAR

WRF ARW User's Guide - MMM - UCAR

WRF ARW User's Guide - MMM - UCAR

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

should be set to a list of prefixes of intermediate files, including path information when<br />

necessary. When multiple path-prefixes are given, and the same meteorological field is<br />

available from more than one of the sources, data from the last-specified source will take<br />

priority over all preceding sources. Thus, data sources may be prioritized by the order in<br />

which the sources are given.<br />

As an example of this capability, if surface fields are given in one data source and upperair<br />

data are given in another, the values assigned to the fg_name variable may look<br />

something like:<br />

&metgrid<br />

fg_name = '/data/ungribbed/SFC', '/data/ungribbed/UPPER_AIR'<br />

/<br />

WPS<br />

To simplify the process of extracting fields from GRIB files, the prefix namelist<br />

variable in the &ungrib record may be employed. This variable allows the user to control<br />

the names of (and paths to) the intermediate files that are created by ungrib. The utility of<br />

this namelist variable is most easily illustrated by way of an example. Suppose we wish<br />

to work with the North American Regional Reanalysis (NARR) data set, which is split<br />

into separate GRIB files for 3-dimensional atmospheric data, surface data, and fixed-field<br />

data. We may begin by linking all of the "3D" GRIB files using the link_grib.csh<br />

script, and by linking the NARR Vtable to the filename Vtable. Then, we may suitably<br />

edit the &ungrib namelist record before running ungrib.exe so that the resulting<br />

intermediate files have an appropriate prefix:<br />

&ungrib<br />

out_format = 'WPS',<br />

prefix = 'NARR_3D',<br />

/<br />

After running ungrib.exe, the following files should exist (with a suitable substitution for<br />

the appropriate dates):<br />

NARR_3D:2008-08-16_12<br />

NARR_3D:2008-08-16_15<br />

NARR_3D:2008-08-16_18<br />

...<br />

Given intermediate files for the 3-dimensional fields, we may process the surface fields<br />

by linking the surface GRIB files and changing the prefix variable in the namelist:<br />

&ungrib<br />

out_format = 'WPS',<br />

prefix = 'NARR_SFC',<br />

/<br />

Again running ungrib.exe, the following should exist in addition to the NARR_3D files:<br />

NARR_SFC:2008-08-16_12<br />

NARR_SFC:2008-08-16_15<br />

NARR_SFC:2008-08-16_18<br />

...<br />

<strong>WRF</strong>-<strong>ARW</strong> V3: User’s <strong>Guide</strong> 3-23

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!