Comprehensive evaluation of iAMAS (v1.0) in simulating Antarctic meteorological fields with observations and reanalysis

Regular latitude-longitude grids in global simulations encounter polar singularities in the Arctic and Antarctic regions. In contrast, unstructured meshes have the potential to overcome this issue; however, so far, the performance of unstructured meshes in polar areas has barely been investigated. This study investigates the efficacy of unstructured meshes over Antarctica using the integrated Atmospheric Model Across Scales (iAMAS, v1.0) with multi-source observations. Four mesh configurations of the iAMAS model were assessed, varying in resolution (120, 60, 16, and 4 km) over the Antarctic region. The study evaluates the performance of the iAMAS simulation for both the surface layer and the upper meteorological fields (temperature, pressure, specific humidity, and wind speed), comparing simulations with data from the fifth-generation ECMWF reanalysis (ERA5) and measurements from automatic weather stations and radiosondes. The results indicate that the iAMAS model does not exhibit the polar singularity issue observed in ERA5, where the ERA5 with regular latitude-longitude grids significantly underestimates wind speeds at the polar grid center. In the relatively flat region of East Antarctica, all four iAMAS experiments at various resolutions demonstrate comparable and even superior performance in simulating temperature and wind speed compared to ERA5. In regions with complex terrain, such as near the Transantarctic Mountains, the iAMAS model (particularly at coarse grid resolutions like 120 km) exhibits a cold bias and stronger wind speeds, consistent with biases identified in other Antarctic simulations using regional models. In particular, mesh refinement at 4 km in complex terrains significantly enhances iAMAS's accuracy in simulating the meteorological fields for both the surface layer and upper atmosphere, suggesting that a grid resolution of 4 km (or even higher) is optimal in such regions. In contrast, in flatter areas, such as the high East Antarctic Plateau, increases in grid resolution yield minimal improvements in simulation accuracy, and a 60 km grid resolution appears sufficient.