When driving toward the Death Valley park, in the eastern California (USA), you may face some very local dust storms due to gust or high wind speed within the area. That was my case, in April 2017, when travelling in California. Dust storm in local area or dust long-range transport in the atmosphere are quite significant and can be monitored through satellite imageries.
Dust belongs to the family of aerosols. It is characterized as dry solid particles suspended in the atmosphere that can range in size from sub-micron to several tens of microns. Dust sources are very variable: e.g. soil, salt spray, smoke from forest fires and industries, volcanic eruptions, extraterrestrial sources (i.e. meteor dust), and organic materials, such as bacteria, plant pollen, animal hairs, and human skin cells.
A dust storm is issued from strong winds, also named aeolian dust, and follows a drought period over an arid area (such as the Death valley) composed of normally arable land, thus providing the very fine particles of dust. Strong winds are able to remove mostly silt-sized material, deflating susceptible surfaces. They can also be associated with gust fronts or thunderstorm outflows.
A dust storm usually arises suddenly like a moving dust wall covering a distance of several kms and a depth of a few kms. Ahead of the dust wall the air is very hot and the wind is light.
The presence of these dry particles (like all the aerosols) affect not only climate and air quality, but also the atmospheric satellite measurements devoted to gaseous pollutants (for example NO2, Chimot et al., 2016) in a similar way as our eyes: 1) a shielding effect: they reduce the visibility, masking then partially or totally the elements present behind / below them, 2) enhancement effect: they may increase the brightness of the elements before / ahead of them.
According to the USA weather nomenclature, if blowing dust reduces visibility to between 5/8 and 5/16 statute mile, a “dust storm” is reported; if the visibility is reduced to below 5/16 statute mile, it is reported as a “severe dust storm”.
More information?
- Dust particles and dust transport according to the American Meteorological society (AMS) here
- Chimot et al., 2016: Chimot, J., Vlemmix, T., Veefkind, J. P., de Haan, J. F., and Levelt, P. F.: Impact of aerosols on the OMI tropospheric NO2 retrievals over industrialized regions: how accurate is the aerosol correction of cloud-free scenes via a simple cloud model?, Atmos. Meas. Tech., 9, 359-382, doi:10.5194/amt-9-359-2016, 2016. here
- My page on aerosols here
- Dust storms monitored by NASA and MODIS space-borne sensors here
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