Modifications to the Rapid Update Cycle Land Surface Model (RUC LSM) available in the Weather Research and Forecast (WRF) model
The land-surface model (LSM) described in this manuscript was originally developed as part of the NOAA Rapid Update Cycle (RUC) model development effort and, with ongoing modifications, is now used as an option for the WRF community model. The RUC model and its WRF-based NOAA successor, the Rapid Refresh (RAP), are hourly updated and have an emphasis on short-range, near-surface forecasts including aviation-impact variables and pre-convective environment. Therefore coupling to this LSM (hereafter, RUC LSM) has been critical to provide more accurate lower boundary conditions. This paper describes changes made to the RUC LSM since earlier descriptions, including extension from 6 to 9 levels, improved snow treatment, and new land-use data from MODIS.
The RUC LSM became operational at the NOAA National Centers for Environmental Prediction (NCEP) as part of the RUC from 1998–2012 and as part of the RAP from 2012 through present. The simple treatments of basic land-surface processes in the RUC LSM have proven to be physically robust and capable of realistically representing the evolution of soil moisture, soil temperature, and snow in cycled models. Extension of the RAP domain to encompass all of North America and adjacent high-latitude ocean areas, necessitated further development of the RUC LSM for application in the tundra permafrost regions and over Arctic sea ice. Other modifications include refinements in the snow model and a more accurate specification of albedo, roughness length and other surface properties. These recent modifications in RUC LSM are described and evaluated in this paper.