Jin, Jiming and Hongping Gu, Utah State University,
Michael B. Ek, Environmental Modeling Center, National Centers for Environmental
Prediction
A one-dimensional
physically-based lake model was coupled with the Weather Research and Forecasting
(WRF) model to improve lake-effect precipitation simulations for the Great
Lakes region. Initial simulations with the WRF-Lake model show that the
seasonal cycle of lake surface temperature (LST) was greatly exaggerated
especially for the deep lakes such as Lake Superior. The exaggerated LST
seasonal cycle results from insufficiently simulated turbulent mixing in the
lake. A series of sensitivity tests with WRF-Lake were performed to optimize
the eddy diffusivity that controls water mixing in the lake scheme and is a
function of surface wind and roughness length. The coupled model is able to
realistically reproduce the LST seasonal cycle with the optimized eddy
diffusivity. In addition, we performed multi-year simulations at 10 km
resolution for the period of 2003-2008 forced with 32 km resolution North
American Regional Reanalysis data to validate the coupled model. The results reveal that the simulated
LSTs are in very good agreement with surface buoy observations and Moderate
Resolution Imaging Spectroradiometer satellite data. The realistic LST
simulations also generate more accurate lake-effect precipitation when compared
with that produced by the release version (3.2) of WRF without a lake scheme.