x Abu Dhabi, UAESunday 23 July 2017

Autumn officially begins on Thursday

The autumn equinox, the astronomical moment when summer gives way to autumn, occurs at 7.09am on Thursday bringing cooler temperatures.

By the end of the week, areas far from the coastline will be reaching morning lows of around 20°C with coastal areas, like Abu Dhabi, about five degrees warmer.
By the end of the week, areas far from the coastline will be reaching morning lows of around 20°C with coastal areas, like Abu Dhabi, about five degrees warmer.

The days grow cooler. The autumn equinox, the astronomical moment when summer gives way to autumn, occurs at 7.09am on Thursday. "During the autumn equinox, the Sun is directly over the equator, which makes the length of the day and night equal," said Ahmed Sajwani, a weather blogger in the UAE. "By the last two days of September, nights will be slightly longer in the northern hemisphere, and they will keep on increasing."

The shorter days in autumn means the sun shines for less time over the northern half of the world, so less heat reaches the surface in the UAE. Some cooling already started on September 1, which was the beginning of meteorological autumn. But the trend picks up significantly as the days grow shorter. "Every day, the UAE and the rest of this half of the world will be losing more heat than it gains from the Sun," he said.

In addition, the northern hemisphere will be getting less heat because it will be tilted away from the sun at an angle of 23.5 degrees, as opposed to spring and summer when it is tilted in the other direction, said George Odhiambo, assistant professor of geography and specialist in hydrometeorology at UAE University. The weather forecast for this week has been sunny and hot, with temperatures reaching the high 30s and low 40s. By the end of the week, areas far from the coastline will already be reaching morning lows of around 20°C with coastal areas about five degrees warmer.

Next month, the average highs will be between 36 and 37°C. "You might still get a few days of 40°C, especially in the beginning of the month," said Mr Sajwani. With lower air temperature, the humidity will be easier to bear. October is also one of the foggiest times of the year - particularly early in the morning. "Any humid night you see in October, you can expect fog in the early morning," he said.

November will bring an increased chance of rain. By late December, the maximum air temperature will be 25°C. That will be a far cry from the summer heat - when the dry desert winds pushed temperatures as high as 50°C, said Mr Sajwani. The National ran its own weather experiment throughout summer, recording temperatures in the very high forties on a regular basis, especially during August. Globally, two US studies - by the Nasa Goddard Institute for Space Studies and the National Climatic Data Center - found that the first half of 2010 was the hottest since modern temperature measurements began. A study by the British Met Office found the first half of 2010 the second-hottest on record, preceded by 1998. The UAE's National Center of Meteorology and Seismology has not yet provided similar figures.

It is too soon to say whether this summer will break any UAE records, said Prof Odhiambo, who is waiting to review statistics provided by the meteorology centre in Abu Dhabi. However, Mr Sajwani said one event this summer definitely set a high-water mark. Cyclone Phet, which lashed Oman in June, was one of the region's strongest storms on record. While the Arabian Sea is prone to tropical storms between May and June and late September and early November, the bad weather usually does not reach as far as Oman. Further, said Mr Sajwani, the storms are usually not strong enough to cause serious destruction. Yet Phet and Gonu, which hit the UAE in 2007, caused significant damage. It was also unusual that the two storms were so close together.

Mr Sajwani said one factor could be climate change. "This is alarming," he said. "But it is a new trend, so nobody can make conclusions still." Prof Odhiambo expressed a similar opinion, pointing to other weather events such as the Russian heat wave and flooding in Pakistan. "Globally this year we had extreme weather events," he said. "Generally, these events are linked to climate change." He said climate change caused by disruptions to the atmosphere because of the large-scale burning of fossil fuels manifests differently around the world, which combined with the scarcity of recent data makes conclusions difficult.

vtodorova@thenational.ae This article has been altered to remove an incorrect reference to the days getting shorter from now.