Mild But Prolonged Surge of Saharan Dust Forecast Into May

As of 7:30 PM Tuesday 28th April 2020, air quality is at good levels across Trinidad and Tobago, with Saharan dust concentrations mild. Note that localized reduced air quality will occur in areas with smoke and fires.

Visibility across Trinidad and Tobago is at 10 kilometers.

Most islands across the Eastern Caribbean are experiencing good air quality based on U.S. standards as of 7:30 PM Tuesday 28th April 2020.

The Environmental Management Agency (EMA) air quality monitoring stations are presently recording AQI values at good to moderate levels in Trinidad and Tobago 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.

Air Quality Index at Environmental Management Agency‘s (EMA) Air Quality Monitoring Stations Across Trinidad. Note these AQI values are to Trinidad and Tobago air quality standards.

What we expect

Based on the latest dust modeling, dust concentrations are forecast to remain mild on Wednesday, with an initial brief surge on Thursday, reducing air quality to moderate.

On Friday, a surface to low-level trough is forecast to reduce Saharan Dust concentrations, improving air quality briefly before the second, more prolonged surge arrives by late Saturday.

A strong high-pressure system will build in following this trough, setting up a favorable wind regime to transport Saharan Dust from Western Africa to the Eastern Caribbean through the first week of May 2020, with no end within the foreseeable (and model-able) future. The good news is that the overall concentrations will only reduce air quality to moderate levels at its worst.

Hence, air quality will continue to fluctuate between good and moderate levels, with your local air quality varying due to vehicle exhaust and nearby fires instead of prevailing Saharan Dust.

00Z April 28th, 2020, CAMS Copernicus Atmospheric Monitoring Tropical Atlantic Dust Aerosol Optical Depth showing Saharan Dust. Credit:
5-Day Air Quality Index (based on United States EPA Standards), Saharan Dust Forecast For Trinidad and Tobago. Saharan Dust is forecast to fluctuate between good and moderate concentrations across Trinidad and Tobago over the next 5 days.

What does this mean for you?

For the general population, little to no impacts are forecast beyond reduced visibility. For sensitive groups, such as children, the elderly and persons who suffer from respiratory ailments and allergies, you may need to avoid prolonged exertion outdoors. See below for more detail in the Saharan Dust forecast.

Good Air Quality

Good Air Quality

Level 1 AQI – 0 to 50

What does this mean for you?

At this level, air quality is considered satisfactory, and air pollution poses little or no risk to public health. It’s a great day to be active outside.

Who needs to be concerned?

No one.

What should you do?

Sensitive Groups: Sensitive groups, children and the elderly do not need special protection.

Air purification: It is recommended to run an air purifier in auto-mode, so it automatically reacts to changes in air quality.

Ventilation: It is good for ventilation.

Masks: No masks are needed.

Outdoor Activity: Very suitable for outdoor exercise and activities.  

Moderate Air Quality

Moderate Air Quality

Level 2 AQI – 51 to 100

What does this mean for you?

Air quality is acceptable; however, for some pollutants, there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution.

Who needs to be concerned?

Unusually sensitive people: Consider reducing prolonged or heavy exertion. Watch for symptoms such as coughing or shortness of breath. These are signs to take it easier.

Everyone else: It’s a good day to be active outside.

What should you do?

Sensitive Groups: Sensitive groups such as those with respiratory ailments, children and the elderly are advised to reduce outdoor physical exertion, and reduce the time of their stay outdoors, especially in areas with heavy traffic.

Air purification: At this level, the air is slightly polluted. It is recommended to turn on your air purifier, running at a low level, at a minimum.

Ventilation: Please close windows, as the air is slightly polluted.

Masks: Wearing a mask during outdoor activity is recommended, particularly in areas with heavy traffic.

Outdoor Activity: It is recommended to stay indoors and avoid outdoor exercise.

The surges of dust during this time of year are due to the Harmattan, a season in the West African subcontinent that occurs between the end of November and the middle of March. During this season, a predominant northeasterly trade wind (dubbed the Harmattan Winds) blows from the Sahara Desert over Western Africa into the Gulf of Guinea.

The Harmattan Winds over Central & Western Africa (Source)
The Harmattan Winds over Central & Western Africa (Source)

During this period, a ridge of high pressure stays over the central Sahara Desert, and the Intertropical Convergence Zone (ITCZ) 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 and affect the Eastern Caribbean. These Saharan Dust outbreaks tend to be milder in the Eastern Caribbean than the dust outbreaks associated with West African thunderstorms driving dust into the upper atmosphere from April through November.

Sensitive groups such as persons with respiratory ailments, children, the elderly and cardiopulmonary disease should take the necessary precautions on days where dust concentrations degrade air quality to moderate and beyond, as there is more Saharan Dust forecast.

Saharan Dust Precautions
Saharan Dust Precautions
Facebook Comments