Hydrometeorological Consistency and Structural Differences in High-Resolution Atmospheric Forcing Products over the Gulf Coast

Carlos Erazo, Ibrahim Demir

Kilometer-scale meteorological forcing products are increasingly used in hydrologic applications, yet comparable resolution does not ensure consistent atmospheric structure or derived diagnostics. This study compares AORC and NLDAS-3 across the U.S. Gulf Coast and Southeast (Texas to the Carolinas) from 2001–2020 using a common spatial footprint and paired days. Relative to AORC, NLDAS-3 exhibits lower precipitation (PBIAS −8.9%), warmer temperatures (+0.49 °C), reduced shortwave radiation (−10.2 W.m⁻²), and higher specific humidity (+6.0%). Its precipitation occurs more frequently but at lower intensity, with 31–33% lower return levels. Comparisons against 3,329 GHCN-Daily gauges show AORC better reproduces observed rain-day frequency at 97% of stations. Although temperature-based reference evapotranspiration (ET₀) agrees closely with observations (KGE 0.96-0.98), it masks radiation and humidity differences that shift summer Penman–Monteith ET₀ by up to 0.7 mm day⁻¹. Statistical adjustment reduces precipitation bias but leaves event sequencing and cross-variable coupling unchanged. The full evaluation was carried out as an open, reproducible HydroSuite workflow, and its findings show that distributional equivalence does not imply process-structural equivalence.