African dust crosses the Atlantic

Date:
April 20, 2022
Source:
Penn State
Summary:
A beautiful sunset over the Atlantic off the Florida coast, or an
orangey glow in the Texas sky at dusk may be caused by dust from
West Africa, according to researchers who are looking at the paths
of particulate matter in the skies over the Sahara desert and the
semi-arid Sahel.



FULL STORY ==========================================================================
A beautiful sunset over the Atlantic off the Florida coast, or an orangey
glow in the Texas sky at dusk may be caused by dust from West Africa,
according to researchers who are looking at the paths of particulate
matter in the skies over the Sahara desert and the semi-arid Sahel.


==========================================================================
"We are looking at how much dust is being transported into West Africa
in the winter and across the Atlantic in the summer," said Gregory
S. Jenkins, professor of meteorology and atmospheric science, geography,
and African studies, Penn State. "In the winter, it is low in the
atmosphere and in the summer, it is higher in the atmosphere. Dust has
an impact, especially on health." Jenkins and Moussa Gueye, research professor, University of SIne Saloum El- Hȃdj Ibrahima NIASS,
Dakar, Se'ne'gal, modeled annual particulates less than 10 microns (PM10)
from 1960 to 2016.

"We showed that there is a simulated annual downward trend in surface
PM10 concentrations in Senegal and Cabo Verde after the 1980s, which
is similar to earlier findings," the researcher report in Atmospheric Environment. However, the data for summers suggests that there was an
increase in dust over the Western Sahara that was transported to Cabo
Verde suggesting that this Eastern Atlantic dust continued on toward
the U.S. and the Caribbean.

The researchers can measure the amounts of dust that reach the Western
Atlantic near Miami, Barbados and Puerto Rico for example, because there
are ample meteorological and other measurement stations in those areas,
but in West Africa and places like Cabo Verde, there are few ground-based measurement facilities to measure the dust reaching there.

Researchers must then rely on satellite-based measurements, which cannot provide measurement at night. The data collected by ground-based and
satellite instruments is used as the basis for models that estimate
the paths and amounts of dust hitting West Africa in the winter
and the Atlantic and Caribbean in the summer. However, there are so
few measurement stations in Africa -- because the stations require
electricity, cell phones, internet and someone to maintain them --
that the models are somewhat incomplete.



========================================================================== "With the very limited measurements we have from West Africa compared
to our measurement, we run the models and provide estimates," said
Jenkins. "We know that the model timing is correct, but we don't know
how much the few stations we have are biasing our results." According to Jenkins, currently, the best system is in Nigeria where the stations are
25% less costly, but they still need reliable electricity and internet. He notes however, that Cabo Verde does have reliable Wi-Fi and he would
like to put particulate matter stations on each of the islands.

According to Jenkins, the model simulations reproduce the trends
seen in the past, however, none of the models simulate the dust
correctly. Knowledge of exactly where the dust is going at any time and
how much dust exists at the ground level is important. Estimates suggest
that West Africa will have a population of a billion by 2070. Because this
dust in the air can cause respiratory problems and may carry pathogens,
knowing when to stay out of the dust is important.

"The dust will have lots of impact in West Africa," said Jenkins. "But
in the U.S., we also want to know what happens in the future. I think
there is good reason to say there will be more dust in the future."
Jenkins would like to build a particulate matter system across Africa so
that there are sufficient data to refine the models. The system would also
be able to warn people with, for example, asthma, when to stay inside.

One concern of the researchers is that they know that this Saharan dust transport may change because of climate change in the future.

Penn State's Alliance for Education, Science, Engineering and Design in
Africa supported this work.


========================================================================== Story Source: Materials provided by Penn_State. Original written by
A''ndrea Elyse Messer.

Note: Content may be edited for style and length.


========================================================================== Related Multimedia:
* Squall_lines_of_dust ========================================================================== Journal Reference:
1. Gregory Jenkins, Moussa Gueye. Annual and early summer variability
in
WRF-CHEM simulated West African PM10 during 1960-2016. Atmospheric
Environment, 2022; 273: 118957 DOI: 10.1016/j.atmosenv.2022.118957 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/04/220420170458.htm

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