Hazy and dull skies at Store Bay, Tobago on Wednesday afternoon as dense Saharan Dust blankets the island. (Kenneth Bissoon)
On April 7th, 2021, a dense surge of Saharan Dust reached initial peak concentrations across Trinidad and Tobago, with higher concentrations generally remaining north of Trinidad. Tobago recorded air quality throughout the day at unhealthy levels for the entire population. At this air quality index level, everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects.
As the afternoon progressed, the Environmental Management Agency (EMA) air quality monitoring stations at Signal Hill, Tobago began recording air quality levels that were considered hazardous for everyone’s health. These measurements are based on PM2.5 (particulates the size of 2.5 micrometers and smaller, usually associated with increases in Saharan Dust, vehicle exhaust, and smoke) and PM10 particulates. The sensor then failed and has had no subsequent readings.
Across Trinidad, air quality levels were generally moderate across Central and South Trinidad while unhealthy for sensitive groups across Northern Trinidad based on EMA’s air quality monitoring stations located at San Fernando, Point Lisas, and Beetham.
Though higher concentrations of Saharan Dust were present across Tobago, visibility across the island remained near 9 kilometers while across Trinidad, visibility dropped to 7 kilometers at times.
The Saharan Dust Forecast
Elevated and significant Saharan Dust concentrations are forecast to remain present across T&T and the Windward Islands through late Sunday. A secondary peak in concentrations is forecast on Saturday, which may significantly affect air quality and reduce visibility.
While some improvement is forecast between Sunday and Monday, periodic surges are forecast through next week with air quality remaining degraded.
Across Trinidad, air quality will fluctuate between levels that are moderate to unhealthy for sensitive groups. Across Tobago, air quality will fluctuate between levels that are unhealthy for sensitive groups to unhealthy, at times increasing to very unhealthy levels and even hazardous at points.
A high-pressure system dominating, across the Atlantic, is producing strong easterly trade winds. These winds have become a conveyor belt for a significant and prolonged surge of Saharan Dust into mid-April.
What does this mean for you?
For Trinidad, members of sensitive groups may experience health effects. The general public is not likely to be affected. There is an increasing likelihood of respiratory symptoms in sensitive individuals, aggravation of heart or lung disease, and premature mortality in persons with cardiopulmonary disease & the elderly.
For Tobago, everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects. There may be increased aggravation of heart or lung disease and premature mortality in persons with cardiopulmonary disease and the elderly; increased respiratory effects in the general population. Everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects.
We’re in a period where a ridge of high pressure stays over the central Sahara Desert. The Intertropical Convergence Zone (ITCZ) also remains over the Gulf of Guinea.
The Harmattan wind accelerates when it blows across the mountain massifs of Northwest Africa. If its speed is high enough and it blows over dust source regions, it lifts the dust and disperses it.
Dust that makes it into the upper levels of the atmosphere can then get transported across the Atlantic Ocean. The plumes of dust eventually affect the Eastern Caribbean.
Saharan Dust outbreaks from December through early April tend to be milder in the Eastern Caribbean than in late April through November. During the latter period, those dust outbreaks are associated with West African thunderstorms driving dust into the upper atmosphere.