HR: 1340h
AN: A53A-0861    [Abstracts]
TI: The Impacts of Vegetation Growth on the Development of the North American Monsoon System (NAMS)
AU: Yang, Z
EM: liang@mail.utexas.edu
AF: The Department of Geological Sciences, The Univ. of Texas At Austin, Austin, TX 78712 United States
AU: * Niu, G
EM: niu@geo.utexas.edu
AF: The Department of Geological Sciences, The Univ. of Texas At Austin, Austin, TX 78712 United States
AB: The present study is to explore the impacts of vegetation growth on the developments of the North American Monsoon System (NAMS) by using the newly-released Weather Research and Forecasting (WRF) model version 2.02 coupled with different land schemes. To represent vegetation growth, we incorporate an interactive vegetation canopy (IVC) scheme, which calculates the vegetation carbon budgets (carbon assimilation, carbon allocation to leaf, stem, root, and wood, and respiration) and leaf area index (LAI), into the NOAH land scheme in WRF. LAI is exponentially transformed into fractional vegetation cover (Fveg) to couple with NOAH. A series of experiments are conducted from June 1 to August 31 of 2002 by using WRF with different land schemes, 1) SLAB, which predicts soil temperature but with constant soil moisture and no vegetation, 2) NOAH, which predicts soil temperature and soil moisture but with constant Fveg, 3) NOAH/SWF, which is based on NOAH but the root water uptake factor is modified to be close to a step function instead of a linear function of soil moisture, 4) NOAH/IVC, which is the same as NOAH/SWF but linked to IVC, and 5) NOAH/IVCR, NOAH/IVC with deeper roots. The model results are as follows. 1), the rainfall is strongly sensitive to land surface processes. SLAB fails to simulate the monsoon rainfall in all months, while NOAH produces comparable rainfall to observations except for August. 2) NOAH/SWF increases evapotranspiration (ET) and rainfall in southern NAMS region in August. 3) NOAH/IVC significantly improves the rainfall simulation in the southern NAMS and Southern Great Plain (SGP), especially in August. 4) Increasing rooting depth does not increase ET and rainfall in this study because the deeper soil layer is even drier than its upper layers when the model is initialised with the NCEP/NCAR Reanalysis. This indicates a more accurate initialization of soil moisture or a longer peroid of integration may be required.
UR: http://www.geo.utexas.edu/climate/Research/publications.htm
DE: 1851 Plant ecology
DE: 1610 Atmosphere (0315, 0325)
DE: 1620 Climate dynamics (3309)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting