Variability in airborne particles larger than sand flux for distance scales larger than 200 m was observed during wind erosion episodes on the northeast side of a dry lake bed (Owens Lake). Measurements were made during erosion episodes on a ~3-km line of wind measuring and sand flux collecting instruments. Data were selected for winds that (1) aligned with the instrument line and (2) had mean speeds cubed at 4-m heights at the beginning, middle, and end of the line that differed by less than 5% (i.e., mean wind speeds differed by less than 1.7%). Four mechanisms were determined to cause the large-scale differences in the mass flux profiles. In order of their importance, the mechanisms are as follows: (1) change of the drag coefficient (or the ratio u*/U, where u* is wind friction velocity and U is mean wind speed from place to place), this is a measure of variability in roughness height; (2) particle limitation (depletion of the loose available erodible material on the surface); (3) variation of the threshold friction velocity; and (4) the Owen effect (the increase of u*/U with U). ¿ 1997 American Geophysical Union