Impacts of tiled land cover characterization in the Model for Prediction
Across Scales-Atmosphere (MPAS-A)
Abstract
Parameterization of subgrid-scale variability of land cover
characterization (LCC) is an active area of research, and can improve
model performance compared to the dominant (i.e., most abundant tile)
approach. The “Noah” land surface model implementation in the global
Model for Predictions Across Scales-Atmosphere (MPAS-A), however, only
uses the dominant LCC approach that leads to oversimplification in
regions of highly heterogeneous LCC (e.g., urban/suburban settings).
Thus, in this work we implement a subgrid tiled approach as an option in
MPAS-A, version 6.0, and assess the impacts of tiled LCC on
meteorological predictions for two gradually refining meshes (92-25 and
46-12 km) focused on the conterminous U.S for January and July 2016.
Compared to the dominant approach, results show that using the tiled LCC
leads to pronounced global changes in 2-m temperature (July global
average change ~ -0.4 K), 2-m moisture, and 10-m wind
speed for the 92-25 km mesh. The tiled LCC reduces mean biases in 2-m
temperature (July U.S. average bias reduction ~ factor
of 4) and specific humidity in the central and western U.S. for the
92-25 km mesh, improves the agreement of vertical profiles (e.g.,
temperature, humidity, and wind speed) with observed radiosondes, and
there is a general decrease in error for precipitation in the U.S.;
however, there is increased bias and error for incoming solar radiation
at the surface. The inclusion of subgrid LCC has implications for
reducing systematic warm biases found in numerical weather prediction
models.