Featured Research: DRI scientists analyze origins of the Saharan dust plume

Featured Research: DRI scientists analyze origins of the Saharan dust plume

On June 18, 2020, NASA-NOAA’s Suomi NPP satellite captured this visible image of the large light brown plume of Saharan dust over the North Atlantic Ocean. The image showed that the dust from Africa’s west coast extended almost to the Lesser Antilles in the western North Atlantic Ocean. Credit: NASA Worldview.


 

In late June 2020, a phenomenon known as the Saharan dust plume made headlines in the U.S., as warm, dry winds from northern Africa carried an unusually thick layer of dust more than 5,000 miles across the Atlantic Ocean into parts of the southeastern US, Puerto Rico, and Caribbean.

The arrival of this African dust cloud may have seemed unusual to residents of Florida and other Gulf-coast states, who experienced several days of darkened skies, degraded air quality and spectacular sunsets, but it came as no surprise to DRI Professor Emeritus Michael Kaplan, Ph.D., and Saroj Dhital, M.S., who have been working to understand the origins of Saharan dust plumes for some time.

Dhital, a graduate researcher with DRI’s Division of Atmospheric Sciences in Reno, joined DRI in 2016 as a member of Kaplan’s research group. He is originally from Nepal, and holds a master’s degree in Atmospheric Physics from Tribhuvan University in Kathmandu. In his doctoral work, Dhital is studying the weather patterns and processes that are responsible for large-scale Saharan dust storms that move north from Africa toward Europe and the Tropical Atlantic.

DRI researcher Saroj Dhital

Saroj Dhital presents research on a 2017 dust case at the 2019 AGU Fall meeting.

Working in collaboration with Kaplan and researchers from Spain and Germany, Dhital has been actively involved in an effort to analyze case studies of extreme African dust plumes that impacted the Iberian Peninsula, in the southwest corner of Europe, during 2007, 2008, and 2016. In a new paper in the Journal Atmospheric Environment, Dhital and his colleagues examine the weather patterns and processes that occurred before each one of these major dust events.

“What we are trying to see in this research is what are the precursors before the formation of the dust system,” Dhital explained. “If we can see those types of features in the weather predictions, we could then possibly forecast that there will be a dust storm.”

The analyses of these case studies involve the observational datasets and high-resolution Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) simulations. Numerical simulations are performed inside the National Center for Atmospheric Research (NCAR) high-performance computer, “Cheyenne”.

“Because this area of the Earth is virtually uninhabited, there are almost no surface observations,” Dhital explained. “Remote sensing via satellites and numerical simulations employing a state-of-the-science computer model are our only way of diagnosing the physics of this phenomenon.”

The technology involves the NASA A-train satellite instruments and the supercomputer at NCAR, which can perform more than a trillion operations per second. Without both forms of powerful information processing technology, little would be understood about Sharan dust storms and their long-range transport of dust.

Above: WRF-Chem simulated dust transport video from a 2017 case study that shows the emission of dust over North Africa and subsequent transport towards the tropical Atlantic Ocean (Cape Verde Islands). Credit: Saroj Dhital.

Dhital and his team have recently submitted a second paper for publication on a case study of a 2017 Saharan dust outbreak over the Cape Verde Islands, which lie 650km off the coast of Senegal, West Africa, and is shown in the simulation above. This dust plume led to significant disruptions of local air traffic – disruptions that could have potentially been managed differently if we had the ability to forecast these dust storms or provide early warning to residents.

Additionally, the dust represents a major health hazard as it combines with other pollutants to create respiratory stress in people with lung and breathing problems. This could exacerbate the effect of the COVID-19 epidemic on vulnerable populations in Europe and elsewhere.

”Knowing more about the conditions that lead to dust storms is critically important for operational forecasting and in the development of an early warning system,” Dhital said. “Our research group is now analyzing finer scale meteorological details involved in 2007, 2008, and 2016 dust storm cases utilizing observational and high-resolution WRF-Chem simulations, and we look forward to sharing our findings.”


To learn more about the work of Kaplan, Dhital and their colleagues, read their new paper “Large scale upper-level precursors for dust storm formation over North Africa and poleward transport to the Iberian Peninsula. Part I: An observational analysis” in Atmospheric Environment: https://www.sciencedirect.com/science/article/abs/pii/S1352231020304209?via%3Dihub 

New study identifies atmospheric conditions that precede wildfires in the Southwest

New study identifies atmospheric conditions that precede wildfires in the Southwest

Reno, Nev. (January 3, 2018): To protect communities in arid landscapes from devastating wildfires, preparation is key. New research from the Desert Research Institute (DRI) in Reno may aid in the prevention of large fires by helping meteorologists and fire managers in the Southwestern U.S. to forecast periods of likely wildfire activity.

Each summer, from June through September, a weather pattern called the North American monsoon brings thunderstorms to the Southwestern U.S., with lightning that often sparks wildfires.

The new study, which published in the International Journal of Climatology, examined twenty common weather patterns that occur during the North American monsoon season, and identified relationships between certain weather patterns and times of increased fire activity.

One of the most problematic weather patterns, the team learned, was when dry and windy conditions gave way to lightning storms in May and June – a time when fuels tended to be at their driest and monsoon rains had not yet soaked the region with added moisture. When lightning storms were followed by another hot, dry, windy period, increased fire activity was even more likely.

“A lot of fire meteorologists know from experience that this is how things happen, but our study actually quantified it and showed how the patterns unfold,” said lead author Nick Nauslar, Ph.D., who completed this research while working as a graduate student at DRI under Tim Brown, Ph.D. “No one had ever really looked at large fire occurrence in the Southwest and how it related to atmospheric patterns.”

To identify problematic weather patterns, Nauslar and his team looked at monsoon season weather data collected from April through September over the 18-year period from 1995-2013. They then classified wildfire activity over the same period into days or events that were considered “busy” by fire managers in their study area, and used an analysis technique called Self-Organizing Maps to detect relationships between the two datasets.

In addition to identifying relationships between specific weather patterns and fire activity, their analysis also looked for patterns in wildfire occurrence and fire size throughout the season. Analysis of more than 84,000 wildfires showed that although July was the month that the most wildfires occurred, wildfires that occurred during the month of June (prior to the arrival of much monsoonal moisture) were more likely to develop into large fires. In July and August, when the heaviest monsoonal precipitation typically occurs, the percentage of fires that developed into large fires decreased.

“Our goal with this study was to provide fire weather meteorologists in the region with information to help inform fire forecasts, and I think we were able to identify some important patterns,” said Brown, Director of the Western Regional Climate Center at DRI.

Nauslar, who is now employed as a mesoscale assistant and fire weather forecaster for the National Oceanic and Atmospheric Administration (NOAA) Storm Prediction Center in Norman, Oklahoma, hopes that the findings of this study will help fire managers in the Southwest to proactively identify periods when wildfires are more likely to occur, and to allocate firefighting resources accordingly.

“I think a lot of what we learned confirms forecaster experience about the types of atmospheric patterns that are problematic with regard to wildfire occurrence in the Southwest,” Nauslar said. “I hope that people in operations can really use this information, and help refine it and build upon it.

Other DRI scientists who contributed to this research included Benjamin Hatchett, Ph.D., Michael Kaplan, Ph.D., and John Mejia, Ph.D. The full study, titled “Impact of the North American monsoon on wildfire activity in the southwest United States,” is available online from the International Journal of Climatology: https://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/joc.5899

 

The Desert Research Institute (DRI) is a recognized world leader in basic and applied interdisciplinary research. Committed to scientific excellence and integrity, DRI faculty, students, and staff have developed scientific knowledge and innovative technologies in research projects around the globe. Since 1959, DRI’s research has advanced scientific knowledge, supported Nevada’s diversifying economy, provided science-based educational opportunities, and informed policy makers, business leaders, and community members. With campuses in Reno and Las Vegas, DRI serves as the non-profit research arm of the Nevada System of Higher Education. Learn more at www.dri.edu, and connect with us on social media on FacebookInstagram and Twitter. 

Northern Nevada Science Center
2215 Raggio Parkway
Reno, Nevada 89512
PHONE: 775-673-7300

Southern Nevada Science Center
755 East Flamingo Road
Las Vegas, Nevada 89119
PHONE: 702-862-5400