Land data assimilation system

The community version of LDAS¹⁷ (version 3.4.1) available through the National Center for Atmospheric Research (NCAR) is used to generate SM/ST fields in the present study. The version used includes a glacial ice and sea ice module. It considers four soil layers at 0–10 cm, 10–40 cm, 40–100 cm, and 100–200 cm with a total soil depth of 2 m. The vegetation root depth varies with land use type in the upper 1.5 m of soil. The LDAS is designed for both uncoupled and coupled modes within the ARW²⁸. The advantage is that the LDAS uses the same grid as the Weather Research Forecasting suite of models, sharing the same Noah²⁹ land model and same geophysical parameters (land use, soil texture, terrain height, time-varying vegetation fields) and reduces interpolation errors that affect the coupled model integration. The Noah LSM integrates hydro-meteorological forcing parameters, and static surface fields; and estimates SM, ST, evapo-transpiration, fluxes, interception, and other land variables (complete list available from¹⁷). The Noah-LSM is based on the Penman potential evaporation approach³⁰, the multi-layer soil model³¹, and a primitive simple canopy model³². It is further improved with the addition of complex canopy resistance^33,34 and frozen ground physics³⁵.