v4.0

WRF Pre-processing System Version 4.0

This release includes the following notable changes:

* Introduction of a 'lowres' option for geog_data_res to select coarse resolution
  (typically, 5-arc-minutes) sources for all mandatory static fields. This is
  useful in educational contexts or when the size of the geographical datasets
  must be minimized, e.g., when teaching with WRF/WPS in a Docker container or
  in the cloud.

* New GEOGRID.TBL entry for a pre-computed urban fraction field (FRC_URB2D) based
  on 30-meter NLCD 2011 data.

* A change in the default source of data for the MAXSNOALB and ALBEDO12M fields.
  The new defaults are MODIS-based and higher resolution.

* Two fixes for numerical inaccuracies in the polar stereographic projection.

* A new namelist option for ungrib, pmin, to specify the minimum pressure to
  extract from isobaric datasets.

* A combined Vtable for all CFSR/CFSv2 data, both pressure-level and surface
  fields (Vtable.CFSR).

* Added support for NCAR RDA's ECMWF "ds113.1" dataset.

* Added support for FV3GFS GRIB data.

* Generally, in the v4.0 release of the WPS, there is a move towards a model
  for handling geographical static fields in which all static fields that are
  not required by the default WRF namelist are optional from the viewpoint of
  geogrid.
  - Datasets that were previously mandatory but that are now optional:
    VAR_SSO and LAKE_DEPTH.

Note: There are now three types of downloads for the static, geographical data:
(1) Download the "full-resolution" sources for all default, mandatory fields.
    Use this download for all simulations where accuracy is important.

(2) Download the "low-resolution" sources for all mandatory fields.
    Use this download for testing and educational purposes.

(3) Downloads for individual, optional geographical fields.
    Obtain these datasets as needed by different model options.