1.4 Software Updates and Plans

Gill, David O., National Center for Atmospheric Research

Typical of the annual release, the WRF v3.9 code released in April 2017 includes a few new features that are important to note when considering software and infrastructure upgrades.

The REAL, NDOWN, and WRF codes (along with 3dvar and WRF Chem) support the newly available hybrid vertical coordinate (HVC). The post-processors UPP, NCL, and RIP4 also support the HVC option. By default, the HVC option is turned off at compile-time and at run-time.

A recent and small fix to the threading routines in WRF (plus some environment variables) have given OpenMP + MPI parallelism a good boost.

The WRF system is now hosted on github. We encourage developers to contact us with their github IDs so that they may keep their WRF codes as up-to-date as possible.

The run-time option for selecting physical parameterization schemes has been updated. While user may still request each scheme individually, the default namelists now feature 'tropical' and 'conus' options. The full generality of the per-domain scheme options is still accessible. However the convenience of a recommended set of schemes that are known to work well together (i.e. a suite) is now the default.

The MPAS and WRF model now share the diagnostically rich RIP4 post-processor (with MPAS interpolated first to a regular latitude-longitude projection). By v4.0, this will be a seamless, one-step process.

The metgrid package directly ingests MPAS model output, without any domain re-projection. This allows the full resolution of the MPAS model output to provide initial and lateral boundary conditions to the WRF model.

The Parallel I/O (PIO) library (CISL/NCAR) version 1 is on a branch of the WRF model, providing scalable I/O (mostly we care about "O") performance.

The next major release of the WRF code will be v4.0, slated for Spring 2018. This version of the WRF code will not be backward compatible with older data sets (and vice versa: the new WRF v4.0 data will not work in older versions of the WRF model). The HVC option will be the default, both compile-time and run-time. The moist potential temperature (referred to as the "theta_m mods") will be fully incorporated into the initial and lateral boundary conditions. The structure of the lateral boundary file will no longer include mass coupled fields, just regular tendencies for each field. The physics drivers will start the transition to an interoperable interface, and the physics schemes will include shared options between WRF and MPAS.