Abstract : 1A.9
Sensitivity of model simulated low-level winds in the Central Valley of California to uncertainties in the large-scale forcing and soil initialization

Jian-Wen Bao, Sara Michelson
Jian-Wen.Bao@noaa.gov
NOAA/Earth System Research Laboratory

The sensitivity of the WRF model simulated low-level winds in the Central Valley of (CV) California to uncertainties in the atmospheric forcing and soil initialization is investigated using scatter diagrams. It is assumed that the uncertainties in the atmospheric forcing and soil initialization can be approximated by two operational analyses. First, the sensitivity is illustrated using scatter diagrams and measured in terms of the linear regression of the output from two simulations which differ in either the atmospheric forcing or the soil initialization. The spatial variation of the sensitivity is investigated and linked to the dominant low-level flows within the CV. The results from this study indicate that the WRF simulated low-level winds in the northern CV (the Sacramento Valley, SV) are more sensitive to the uncertainties in the atmospheric forcing than to those in the soil initialization. The simulated low-level winds in the southern most part of the San Joaquin Valley (SJV) are more sensitive to the soil initialization than they are in the SV. In the northern SJV, which is more directly under the influence of the incoming marine flow than either the SV or the southern SJV, the winds are overall more sensitive to the atmospheric forcing than to the soil initialization. This distribution of sensitivity indicates the important roles that the large-scale forcing specified by the lateral boundary conditions and the local forcing associated with the soil state play in controlling the incoming marine flow through Carquinez Strait.