Benchmarking multi-component spatial metrics for hydrologic model
calibration using MODIS AET and LAI products
Abstract
SPAtial EFficiency (SPAEF) metric is one of the most thoroughly metrics
in hydrologic community. In this study, our aim is to improve SPAEF by
replacing the histogram match component with other statistical indices,
i.e. kurtosis and earth mover’s distance, or by adding a fourth or fifth
component such as kurtosis and skewness. The existing spatial metrics
i.e. SPAtial Efficiency (SPAEF), Structural Similarity (SSIM) and
Spatial Pattern Efficiency Metric (SPEM) were compared with newly
proposed metrics to assess their converging performance. The mesoscale
Hydrologic Model (mHM) of the Moselle River is used to simulate
streamflow (Q) and actual evapotranspiration (AET). The two-source
energy balance (TSEB) AET during the growing season is used as monthly
reference maps to calculate the spatial performance of the model. The
Moderate Resolution Imaging Spectroradiometer (MODIS) based Leaf area
index (LAI) is utilized by the mHM via pedo-transfer functions and
multi-scale parameter regionalization approach to scale the potential
ET. In addition to the real monthly AET maps, we also tested these
metrics using a synthetic true AET map simulated with a known parameter
set for a randomly selected day. The results demonstrate that the newly
developed four-component metric i.e. SPAtial Hybrid 4 (SPAH4) slightly
outperform conventional three-component metric i.e. SPAEF (3% better).
However, SPAH4 significantly outperforms the other existing metrics i.e.
40% better than SSIM and 50% better than SPEM. We believe that other
fields such as remote sensing, change detection, function space
optimization and image processing can also benefit from SPAH4.