Conceptual model linking dune morphology, aeolian accretion, and GPR-imaged internal architecture. (a) Cross-sectional morphology of a representative dune under the prevailing wind, showing the principal geomorphic elements, including the stoss slope, dune crest, and lee slope. Wind-driven sand transport carries grains up the stoss slope; after crossing the crest, grains are deposited on the lee side through grainfall, grainflow, and avalanching. (b) Conceptual model of dune internal architecture, illustrating inclined accretion surfaces, cross-bedding, and stage-bounding surfaces formed during dune migration. Variations in grain-size distribution, compaction, pore structure, or moisture content between adjacent depositional layers can produce weak dielectric contrasts and generate detectable internal reflectors in GPR profiles. (c) Schematic plan view of a barchan dune, showing the stoss slope, slipface, horns, and migration direction. Surface morphology, prevailing wind direction, and internal accretion architecture together govern the reflection geometries observed in radar profiles.