I am using NLDAS_NOAH hourly surface runoff (non-infiltrating) for my research and I need more details. How does NLDAS use the Noah model and which runoff scheme is implemented for NLDAS? I have looked through the documentation for NLDAS and the user guide but I am in search for more details on runoff specifically. NASA LDAS data rods webpage is where I am getting the data from.
Regarding your questions, please find the following suggestions from a NASA NLDAS scientist (also NLDAS data provider).
Please check this webpage, http://www.ral.ucar.edu/research/land/technology/lsm.php, with the User's Guide for Noah-2.7.1 at the very top, or http://www.ral.ucar.edu/research/land/technology/lsm/noah/Noah_LSM_USERGUIDE_2.7.1.pdf. Please note that NLDAS-2 uses Noah-2.8, but the runoff code is the same as the Noah-2.7.1 described here.
More details can be found from the source code of NASA Land Information System (LIS). If you are going to download the source, please get the latest version (LIS_public_release_7.2r), available from this page, https://lis.gsfc.nasa.gov/releases .
Please note that, for downloading the LIS code, you need to register first. The link to the registration page is on the right-side of the releases page, or directly on this page, https://lis.gsfc.nasa.gov/source/registration.