Exploring Topography Downscaling Methods for Hyper-Resolution Land
Surface Modeling
Abstract
Hyper-resolution land surface modeling provides an unprecedented
opportunity to simulate locally relevant water and energy cycles.
However, the available meteorological forcing data is often insufficient
to fulfill the requirement of hyper-resolution modeling. Here, we
developed a comprehensive downscaling framework based on
topography-adjusted methods and automated machine learning (AutoML).
With this framework, a 90 m atmospheric forcing dataset is developed
from ERA5 data at a 0.25° resolution, and the Common Land Model (CoLM)
is then forced with the developed forcing data over two complex terrain
regions (Heihe and Upper Colorado River basins). We systematically
evaluated the downscaled forcing and the CoLM outputs against both
in-situ observations and gridded data. The ground-based validation
results suggested consistent improvements for all downscaled forcing
variables. The downscaled forcings, which incorporated detailed
topographic features, offered improved magnitude estimates, achieving a
comparable level of performance to that of regional reanalysis forcing
data. The downscaled forcing driving the CoLM model show comparable or
better skills in simulating water and energy fluxes, as verified by
in-situ validations. The hyper-resolution simulations offered a detailed
and more reasonable description of land surface processes and attained
similar spatial patterns and magnitudes with high-resolution land
surface data, especially over highly elevated areas. Additionally, this
study highlighted the benefits of using mountain radiation theory-based
shortwave radiation downscaling models and AutoML-assisted precipitation
downscaling models. These findings emphasized the significance of
integrating topography-based downscaling methods for hillslope-scale
simulations.