LINKING ATMOSPHERIC MODELS AND DUNE MORPHOLOGY – TESTING A FORWARD MODELING APPROACH
Aspects of the approach may be tested on Earth, where ground truth wind data are often available. We used (1) surface wind data to predict dune orientations in the Arabian Peninsula; and (2) uncalibrated surface winds predicted by a regional climate model (WRF) to predict dune orientations in the Namib Sand Sea. We then compared the observed orientations with those predicted using the forward modeling approach. (1) provides a direct test of dune formation theory, while (2) provides a test of the complete ‘blind’ forward modeling approach.
For (1) we predicted dune characteristics using 2000-2009 wind data for 20 stations in or near dune fields to calculate potential sand flux and thereby GBNT dune orientation and R. GBNT theory was a good predictor of crescentic dune orientation, but performed poorly for small and large linear dunes, which were well-predicted by R. This suggests the crescentic dunes formed in unlimited sand, whereas the linear dunes may have formed in areas with limited sand.
For (2) we used a year of WRF winds at 3km resolution. The match between observed and predicted orientations appears much better for GBNT theory, compared to R (though mismatches remain), which may reflect high sand availability. The next steps are to vary the assumed saltation threshold, and to use winds after calibrating WRF to match nearby observational wind data.