The importance of rare, high-wind events for dust uplift in northern Africa.
Dust uplift is a nonlinear thresholded function of wind speed and therefore particularly sensitive to the long tails of observed wind speed probability density functions. This suggests that a few rare high-wind events can contribute substantially to annual dust emission. Here we quantify the relative roles of different wind speeds to dust-generating winds using surface synoptic observations of dust emission and wind from northern Africa. The results show that winds between 2 and 5 m s-1above the threshold cause the most emission. Of the dust-generating winds, 25% is produced by very rare events occurring only at 0.1 to 1.4% of the time, depending on the region. Dust-producing winds are underestimated in ERA-I, since it misses the long tail found in observations. ERA-I overpredicts (underpredicts) the frequency of emission strength winds in the southern (northern) regions. These problems cannot be solved by simple tunings. Finally, we show that rare events make the largest contribution to interannual variability in dust-generating winds and that ERA severely underestimates this interannual variability.
Institute for Climate and Atmospheric Science, School of Earth and Environment University of Leeds Leeds UK.
Sophie M
SM
Cowie
Institute for Climate and Atmospheric Science, School of Earth and Environment University of Leeds Leeds UK.
John H
JH
Marsham
Institute of Meteorology and Climate Research Karlsruhe Institute of Technology Karlsruhe Germany.
Peter
P
Knippertz
ERA‐Interim; dust emission; interannual variability; northern Africa; surface observations; thresholds
J Geophys Res Atmos. 2013 May 27;118(10):4385-4400
25893153
Geophys Res Lett. 2015 Oct 16;42(19):8208-8215
27667872