The development of the HWRF land surface component

Yihua Wu, Ken Mitchell, Michael Ek, Vijay Tallapragada and Robert Tuleya


The most significant step in the development of the HWRF land surface component in 2007-2008 in NCEP's Environmental Modeling Center (EMC) was the addition of the capability in HWRF to execute the Noah Land Surface Model (Noah LSM) in place of the default GFDL Slab Land Surface Model (Slab LSM). The Noah LSM is the operational LSM in NCEP's operational mesoscale forecast model (Ek et al., 2003). The use of the Noah LSM substantially extends the capability of HWRF by giving it the ability to forecast soil moisture and land surface runoff and to initialize HWRF with realistic initial conditions of soil moisture. In contrast, the GFDL Slab LSM in HWRF uses a time-invariant fixed field of land surface wetness and thus is unable to forecast either changes in soil moisture or land surface runoff response. Other major efforts included testing two different choices of surface layer and PBL physics over land, expansion of HWRF post processing capabilities, and preparing and testing streamflow routing algorithms for near-future use in deriving predictions of river flow from HWRF predictions of land surface runoff.