The September Equinox: what is it and what does it mean for the UAE?

Autumn is almost here. According to the National Centre of Meteorology, the first day of the new season will be September 23, during which both the northern and southern hemispheres will experience equal amounts of daylight. That means 12 hours of day and 12 hours of night.

The arrival of the September equinox marks the beginning of autumn in the northern hemisphere, where the UAE lies, and the start of spring in the southern hemisphere.

The "equinox" specifically refers to the moment when the Sun is directly in line with the equator. Over the next few months, temperatures will incrementally drop and days will become shorter until the arrival of winter in December.

So how does this happen?

It is all about our planet’s tilt towards and away from the Sun. As the Earth orbits the Sun, it rotates on its axis with a certain tilt. When a hemisphere leans closer to the Sun, temperatures rise. When it slants away, temperatures fall.

The two points at which these tilts are at their maximum give us the winter and summer solstices, the longest day of the year and the shortest day of the year, respectively.

For the periods of autumn and spring, the Earth gets a little straighter on its axis. Temperatures are more moderate. Days and nights are more proportioned. These are marked by the equinoxes.

“It is basically an equalisation of daytime and night-time,” says Hasan Hariri, astronomer and chief executive of Dubai Astronomy Group.

What does it mean for UAE residents?

While autumn might be associated with the leaves changing colour in the West, it doesn’t happen in the same way in the Emirates.

“The changing season is marked by more change in activity,” says Hariri. “In the summer, for example, the local pearl divers would go for diving and travel for trade because the days were longer and the seas were calmer.”

As the season changes, they adjust their activities. “Winds will start to pick up and the sea becomes rough, so most of the pearl diving will close out and businesses will reduce their amount of travel because navigation will be difficult,” he explains. He says this was also reflected in agriculture, including the cultivation of dates.

Perhaps the most noticeable difference for residents is the decrease in temperature and the clearer skies, which is good news for astronomy buffs.

“In the summer, sandstorms and moisture in the atmosphere disturbs our view of the sky,” says Hariri. He adds that the decrease in temperature will not only make it more comfortable for people to venture out in the evenings, but the small lashes of rain brought by monsoon winds from the Arabian Sea will help clear out the dust in the sky. This is especially true for mountainous areas.

According to Hariri, residents can look out for Venus, which will rise from the west and can be seen by the naked eye around sunset. Planets like Jupiter and Saturn can be seen as well. Mars will show up in the morning sky, before sunrise.

For Muslims, prayer times during the next few months will be more evenly distributed throughout the day, compared to the summer when the timings were more stretched out.

A version of this story was first published on September 22, 2019