HR: 14:40h
AN: GC23B-05    [Abstracts]
TI: Land/atmosphere Coupling Methodology and Regional Climate Downscaling --- A Study Using the JIFRESSE WRF/SSiB Model
AU: * Xue, Y
EM: yxue@geog.ucla.edu
AF: Department of Geography, University of California, Los Angeles (UCLA), 1225 Bunche Hall, UCLA, Los Sangels, CA 90095, United States
AU: * Xue, Y
EM: yxue@geog.ucla.edu
AF: Department of Atmospheric & Oceanic Sciences and Joint Institute for Regional Earth System Science and Engineering, UCLA, 7127 Math Sciences Building,UCLA, Los Angels, CA 90095, United States
AU: Vasic, R
EM: rvasic@geog.ucla.edu
AF: Department of Geography, University of California, Los Angeles (UCLA), 1225 Bunche Hall, UCLA, Los Sangels, CA 90095, United States
AU: Dudhia, J
EM: dudhia@ucar.edu
AF: National Center for Atmospheric Research (NCAR), 1850 Table Mesa Drive, Boulder, CO 80305, United States
AU: Waliser, D
EM: duane.waliser@jpl.nasa.gov
AF: Department of Atmospheric & Oceanic Sciences and Joint Institute for Regional Earth System Science and Engineering, UCLA, 7127 Math Sciences Building,UCLA, Los Angels, CA 90095, United States
AU: Waliser, D
EM: duane.waliser@jpl.nasa.gov
AF: NASA/Caltech Jet Propulsion Laboratory (JPL), 4800 Oak Grove Drive, Pasadena, CA 91109, United States
AU: Liou, K
EM: knliou@atmos.ucla.edu
AF: Department of Atmospheric & Oceanic Sciences and Joint Institute for Regional Earth System Science and Engineering, UCLA, 7127 Math Sciences Building,UCLA, Los Angels, CA 90095, United States
AB: Land-atmosphere interactions play a crucial role in determining regional climate. To examine the impact of land surface processes on seasonal predictions, we use the Weather Research and Forecast (WRF) model to examine to what extent land surface models and land/atmosphere coupling methods have an impact on seasonal predictions. WRF experiments are designed to run with different choices of land models and coupling methods. The variables under evaluations include precipitation, 2-meter temperature, 200 mb and 850 mb winds, and other land surface parameters. Results from our experiments indicate that land/atmosphere coupling has a significant impact on seasonal predictions. The present study shows a proper coupling between the land surface and atmospheric planetary boundary layer is important in regional climate models (RCMs). However, the coupling problem remains largely unexplored and undiagnosed due to complex processes involved across a range of scales. We illustrate that different coupling methodologies are one of the prime sources producing different downscaling capabilities in RCMs. The land/atmosphere interaction includes exchanges of fluxes of momentum, latent heat, and sensible heat, which are affected by atmospheric stability and land surface conditions. A proper coupling process should cover all these aspects coherently and completely. The coupling strategy in the UCLA JIFRESSE (Joint Institute for Regional Earth System Science and Engineering, a collaboration with JPL) WRF/SSiB (Simplified Simple Biosphere) model will be discussed in this presentation. In particular, our approach will be compared with a number of traditional approaches, such as Louis" parameterization, where the total aerodynamic resistance including both neutral and non-neutral parts is only a function of the Richardson number without a full consideration of vegetation presence. A series of tests using the summer 1998 case have been conducted to quantitatively evaluate the impact of coupling methodology. We show that it has substantial impact on precipitation and large-scale circulation, such as the 200mb wind, on monthly and seasonal scales. We also illustrate that a proper coupling between land and atmosphere greatly enhances the WRF/SSiB's ability in accurately simulating North American regional climate features. Finally, the impact of land surface initial conditions on downscaling will be addressed.
DE: 1622 Earth system modeling (1225)
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
DE: 1637 Regional climate change
DE: 1840 Hydrometeorology
DE: 1854 Precipitation (3354)
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting