The warm Doha fogBy Steff Gaulter
November 01 2014 10:14 PM
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Finally November is with us and the heat has begun to subside. This year the hot weather stayed with us a bit longer than other years. The average maximum temperature this October was over 1°C higher than last year, but the real difference this year was in the overnight temperatures. Last year the average minimum temperature for October was 25°C (78°F), this year it was 28C (82°F). The difference of 3C (4°F) was certainly noticeable and the accompanying humidity didn’t help it feel any cooler either.
The reason for the extra heat and humidity was due to the direction from which the wind was blowing. The prevailing breeze in Qatar is usually from the northwest. This is a dry wind and the lack of moisture means that the temperature can change more readily. If you try to heat humid air, not only do you have to heat the air, but you also have to heat the water in the air, and this takes more energy. As well as being faster to heat, dry air is also quicker to lose heat as well. This means that if the wind comes from the northwest, we often see high temperatures during the day, but at night the temperatures are actually relatively low.
This October, the winds were flowing from the east far more often than usual. An easterly is quite different from our prevailing northwesterly wind. It picks up plenty of moisture from the Gulf, and makes sure that Doha is a very humid place. Our easterly wind made things feel very sticky, and also prevented our temperatures from dropping low during the night.
At this time of year, with the sun sinking southwards for the northern hemisphere’s winter, the temperatures do gradually subside no matter from which direction the wind is flowing. This year the easterly wind simply ensured that the night time stayed hot for as long as possible. The temperatures will continue to ease over the coming weeks and months, until finally, in January, people will start to complain that it’s too cold!
As the heat gradually eases, we usually see some rather thick fog. If you’ve yet to encounter fog in Doha, then it can be a rather strange experience, especially if you’re used to seeing fog on chilly winter mornings. At this time of year the fog in Doha is warm!
If there is enough moisture in the air, fog can form at any temperature. All you need to do is saturate the air. This can either be done by adding moisture to it or, because warm air can hold more water vapour than cool air, simply by cooling it. This is why you see steam rising from the spout of a kettle; the humid air is cooling, and this forces the water vapour to condense into water droplets which we see as steam. This is also the way in which many clouds form; warm air rises and cools, with the moisture condensing into the water droplets within clouds. Fog can also be formed in this way; if the overnight temperature drops low enough, the water vapour will be forced to condense into the tiny water droplets that comprise fog. The temperature at which the fog forms simply depends on the amount of moisture in the air.
Fog generally forms on clear nights, because the temperatures can drop lower with clear skies than under a blanket of cloud. A layer of cloud will prevent the day time heat from escaping. Of course in Doha, we have clear skies for the majority of the year, but another factor which will prevent fog from forming is a breeze, something for which Doha is famous. Often it will only take the lightest of winds to force fog to lift, meaning that low cloud forms instead of fog.
If you are lucky enough to live high up in one of the glittering towers in West Bay, then you are likely to find that fog here can be very beautiful. If you are high enough to be above the fog, then you will have blue skies above you, whilst below you, the buildings will disappear into the grey abyss below you.
If you live on a floor that’s not above the top of the fog, it may pay you to be patient. Slowly, after sunrise, the fog will start to clear. This will initially begin from the top of the fog and slowly work downwards. The sun’s heat gradually warms the air until the water droplets within the fog can turn into water vapour once more and be absorbed into the air. Therefore, if you are not above the fog when you first look out the window, you could be in a few moments’ time.
Obviously fog can also be rather dangerous, particularly if you are driving in it. People here get a bit confused and use their hazard warning lights rather than their fog lights, which isn’t so helpful, and of course they still have a habit of driving too close. It’s also worth bearing in mind that although fog blocks out the visible light, it doesn’t actually screen any of the ultraviolet wavelengths. This leads to the slightly strange situation where you might be unable to see the end of your nose, but you are still at risk of sunburn. Clearly no matter what the weather is in Qatar, the desert sun still prevails.

UNIQUE EXPERIENCE: As the heat gradually eases, we usually see some rather thick fog. If you’ve yet to encounter fog in Doha, then it can be a rather strange experience, especially if you’re used to seeing fog on chilly winter mornings. At this time of year the fog in Doha is warm.

 

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