Earth Sciences Division Berkeley Lab
Climate and Carbon Sciences Program
Research Summaries 2006-2007
UNDERSTANDING THE ROLE OF LAND-SURFACE PROCESSES IN THE REGIONAL CLIMATE SYSTEM: A WRF MODELING STUDY Jiming Jin, Norman L. Miller, and Nicole J. Schegel Contact: Jiming Jin, 510/486-7551, JimingJin@lbl.gov
RESEARCH OBJECTIVES results. Figure 1 shows the winter daily The state-of-the-art Weather maximum temperature observations R e s e a rch and Forecasting (WRF) and simulations. The domain-wide model, developed by the National averaged value for the observation is Center for Atmospheric Research 5.5ºC, and for WRF-CLM3 is 5.0ºC. The (NCAR), is a limited-area, nonhydrodaily maximum temperatures for RUC, static, terrain-following sigma-coordiNOAH, and STD with WRF are 4.9ºC, nate model designed to simulate or 6.2ºC, and 10.4ºC, respectively. The predict regional weather and climate. simulated geographic distributions of The current-release version (2.2) of the temperature for all these models are WRF model includes three land-surquite similar, implying that the temperface schemes—the simple soil thermal ature distribution is more closely re l a td i ffusion (STD) scheme, the Noah ed to the atmospheric forcings than to scheme, and the Rapid Update Cycle the land-surface processes, whereas the (RUC) scheme. We have recently coutemperature magnitude is dominated pled the sophisticated Community by land-surface characterizations. In Land Model version 3 (CLM3) to WRF addition, WRF dramatically overe s t ito better simulate and predict snow, mates precipitation, especially over vegetation dynamics, and related complex topography in the western processes. The objective of this study U.S. no matter which land-surface is to quantify the role of varying levels model is chosen, indicating that precipof complexity in land-surface processFigure 1. The geographic distribution of observed and WRF simulated winter (December, January, and es in the regional climate system, by itation simulations are strongly conFebruary) daily maximum temperature (Unit:°C). A. performing a series of WRF runs with nected with atmospheric processes Observations; B. CLM3; C. Noah; D. RUC; E. STD these four land-surface-scheme over this region. options. Among these four schemes, SIGNIFICANCE OF FINDINGS the STD scheme is the simplest one (both in structure and physics), CLM3 is the most sophisticated, and the complexity The results from WRF with these land-surface schemes level of RUC is comparable with that of Noah. The modeling show that land-surface processes strongly affect temperature analysis shown in this study also gives insight into how the simulations; the WRF-CLM3 with the highest complexity level land-surface-scheme complexity level affects the accuracy of produces the best results. Precipitation is dramatically overesregional climate simulations. timated by WRF for all of the land-surface schemes over the western U.S. analyzed here, and does not show a close relationAPPROACH ship to land-surface processes. Four WRF simulations, one for each land-surface scheme, RELATED PUBLICATION were generated with a 30 km resolution domain that focuses on the western United States. Each simulation period was for 1 Jin, J., N. L. Miller, and N. Schegel, Understanding the role of October 1, 1995, through September 30, 1996. The National Centers land-surface processes in the Regional Climate System: A for Environmental Prediction–Department of Energy (DOE) WRF modeling study. Proceedings of the Annual WRF Reanalysis (NCEP-2) data were used for the WRF initial and laterWorkshop, Boulder, Colorado, 2007. al boundary conditions, with the boundary forcing, including sea ACKNOWLEDGMENTS surface temperature (SST), updated every six hours. Support for this work provided by the California Energy ACCOMPLISHMENTS Commission under Grant 500-02-004. Work performed at Lawrence Berkeley National Laboratory was supported by the The WRF simulations indicate that the most sophisticated D i re c t o r, Office of Science, Office of Biological and land-surface model, CLM3, generated the best temperature simEnvironmental Research, Climate Change Research Division, ulations when compared to the results from the other three land Atmospheric and Radiation Measurement Program, of the U.S. surface models. The simplest model (STD), without a snow and Department of Energy under Contract No. DE-AC03-765F0098. vegetation component, produces the worst
91