It has been three weeks since I last posted, because I had a special guest in town for two weeks. When he left, I had to start preparing students to take their first midterm. I've had some down time to reflect on more marvels and oddities from my time here. I am crafting a few posts to demonstrate them.
Marvel - the cooling power of linen and cotton (and head scarves)
Qatar, like the many countries in the Arabian/Persian Gulf, is hot and humid. The image that comes to mind for most people is a desert .. and much of the Qatar peninsula is a desert. However, due to the warm temperature of the gulf - averaging 32 degrees Celsius year round - the areas near the water have extremely high humidity - around 50-70% in June - September.
In short, it is hot and humid - even at night.
Before I left the United States, I invested in clothing that would be appropriate for the region. The culture is to dress conservatively - I signed a dress code stating that I would wear long pants/skirts that cover the knees and shirts that are half length or longer. For the most part I wear long sleeves and long pants/skirts. These are not the typical clothing I would wear in hot/humid weather.
However, it turns out that loose fitting cotton and linen clothes are just perfect for staying cool. It turns out that linen is exceptionally breathable which allows sweat to evaporate quickly. Chemically speaking - As sweat evaporates, the breaking of forces between water molecules takes energy, so it takes the heat from your body to break the bonds, which allows to cool. Even in high humidity without a breeze, the loose fitting clothing creates a space for the water to evaporate and cool you down.
So - I am incredibly comfortable wearing my linen pants and my long sleeve cotton tops to walk around town. It keeps the sun office.
My go to pants have been a pair of natural linen pants I bought on a whim one week before I left the US. While these are not dressy enough for the office, I wear them any time I go out because they are just comfortable.
Even when I travel to areas where it is more appropriate to wear short sleeves, I find myself wearing a long sleeve shirt to protect my arms from the sun - which helps keep me cool. Andy did the same thing - although with technical shirts. I still prefer my cotton and linen because it just helps me feel cool!
Oddity - Black Linen is actually cool
In Qatar and many other conservative Arab countries - the women wear black from head to toe. They were head scarves like the black hijab and abayas - a long loose gown worn over other clothing. Any scientist knows that black absorbs more heat than white - so why do the women wear black in a hot climate. In traditionally Bedouin cultures, nearly everyone wears black. But why?
It turns out that someone studied this (BBC article) and determined that black reduces solar loads compared to other colors. White animal hairs permit more short wave radiation to transmit through to the skin compared to dark hairs - this means that more dangerous UV radiation can penetrate through the light colored clothing than dark clothing. Additionally - the cooling power of the clothing comes from the breathability (discussed above) and the loose fitting nature. Cooling in the long loose fitting robes comes from a convection current generated between the skin and clothes. In the Nature article, they say that since the cooling comes from the convection current, the color of the clothing does not matter. And since black allows for less penetration of harmful radiation - black robes make sense.
So - thats odd but it works. Here is a photo of me wearing my favorite black linen dress - not as cooling as the full robe but it works!
Additional reading:
Original Nature Study about black bedouin clothing (paywall)
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