Validation of Noah-Simulated Soil Temperature in the North American Land Data Assimilation System Phase 2

Authors

Youlong Xia, I. M. Systems Group, IncFollow
Michael Ek, Environmental Modeling Center of National Centers for Environmental PredictionFollow
Justin Sheffield, Princeton UniversityFollow
Ben Livneh, University of Washington
Maoyi Huang, Pacific Northwest National Laboratory
Helin Wei, I. M. Systems Group, Inc
Song Feng, University of Nebraska—LincolnFollow
Lifeng Luo, Michigan State University
Jesse Meng, I. M. Systems Group, Inc
Eric Wood, Princeton UniversityFollow

Document Type

Article

Date of this Version

2013

Citation

Journal of Applied Meterorology and Climatology 52, February 2013; DOI: 10.1175/JAMC-D-12-033.1

Comments

Copyright 2013 American Meteorological Society

Abstract

Soil temperature can exhibit considerable memory from weather and climate signals and is among the most important initial conditions in numerical weather and climate models. Consequently, a more accurate long term land surface soil temperature dataset is needed to improve weather and climate simulation and prediction, and is also important for the simulation of agricultural crop yield and ecological processes. The North American Land Data Assimilation phase 2 (NLDAS-2) has generated 31 years (1979–2009) of simulated hourly soil temperature data with a spatial resolution of 1/8°. This dataset has not been comprehensively evaluated to date. Thus, the purpose of this paper is to assess Noah-simulated soil temperature for different soil depths and time scales. The authors used long-term (1979–2001) observed monthly mean soil temperatures from 137 cooperative stations over the United States to evaluate simulated soil temperature for three soil layers (0–10, 10–40, and 40–100 cm) for annual and monthly time scales. Short-term (1997–99) observed soil temperatures from 72 Oklahoma Mesonet stations were used to validate simulated soil temperatures for three soil layers and for daily and hourly time scales. The results showed that the Noah land surface model generally matches observed soil temperature well for different soil layers and time scales. At greater depths, the simulation skill (anomaly correlation) decreased for all time scales. The monthly mean diurnal cycle difference between simulated and observed soil temperature revealed large midnight biases in the cold season that are due to small downward long wave radiation and issues related to model parameters.