 |
| Titel |
Size resolved dust emission fluxes measured in Niger during 3 dust storms of the AMMA experiment |
| VerfasserIn |
M. Sow, S. C. Alfaro, J. L. Rajot, B. Marticorena |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 9, no. 12 ; Nr. 9, no. 12 (2009-06-15), S.3881-3891 |
| Datensatznummer |
250007424
|
| Publikation (Nr.) |
 copernicus.org/acp-9-3881-2009.pdf |
|
|
|
|
|
| Zusammenfassung |
| During the 2006 and 2007 special observing periods of the African Monsoon
Multidisciplinary Analysis campaign an original experimental system has been
implemented in Banizoumbou (Niger) for measuring the size-resolved dust
emission flux in natural conditions and documenting the possible influence
of wind speed on its size distribution. The instrumental set-up, associated
methodology, and the quality tests applied to the data set are described
before the results acquired during 2 events of the Monsoon type and 1 of the
convective type are analyzed in detail. In good agreement with the theory of
sandblasting, it is found in all cases that saltation must take place for a
vertical emission flux to be detected. During a particular erosion event,
the magnitude of the vertical flux is controlled by the surface roughness,
which conditions the saltation threshold, and by the wind friction velocity.
The dust flux released by the high energy convective event is also found to
be much richer in very fine (<2 µm) particles than those of the
relatively moderate Monsoon event, which shows that aerodynamic conditions
definitely influence the initial size distribution of the erosion flux as
previously suggested by wind tunnel experiments. However, the size
distribution of the dust released by a given event is fairly constant and
insensitive to even relatively important variations of u*. This is
interpreted as a possible result of the rather long duration (15 min) over
which wind fluctuations must be averaged for computing u*, which could make
it an inadequate parameter for representing the very short response-time
physical processes that are at the origin of fine dust emission at the
measurement sites. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|