Summary: Estimation of the aerodynamic roughness length in arid and semi-arid
regions over the globe with the ERS scatterometer
and Merhez Zribi5
Received 20 August 2004; revised 15 November 2004; accepted 7 February 2005; published 11 May 2005.
 Estimates of the aerodynamic roughness lengths z0 in arid and semi-arid regions are
for the first time provided for the whole globe, using satellite ERS scatterometer
observations. A statistical relationship is derived between the ERS scatterometer
backscattering coefficients and quality in situ and geomorphological z0 estimates. It is a
practical solution to provide realistic roughness maps with large-scale spatial patterns
that are consistent with independent surface characterization. In addition, it makes it
possible to analyze the seasonal and interannual variations of this parameter on a global
basis. The satellite-derived surface roughness parameters have been implemented into
the dust emission scheme of a global dust cycle model. Dust emission computations are
improved when using the ERS derived z0 as input parameter. The spatial correlation
between the TOMS observation frequency and the model dust events increases from
0.34 when using fixed z0 to 0.52 when using the satellite-derived estimates.