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Tuesday, February 05, 2013

Calima: Weather from the Sahara

The much dreaded 'calima' weather  occurs when there is an easterly stream of air coming from the Sahara desert bringing with it a cloud of fine, flour-like dust and sand and sometimes even locusts. It is often associated with easterly gales and hot dry air from the Sahara. In winter it is not too hot because at this time of the year the desert is cooler, but in summer it can feel like a blast from an open oven. The air also becomes extremely dry and can cause breathing difficulties, dry mucous membranes, eye irritation and flu-like symptoms. The sun becomes obscured to appear like a milky disk and visibility is greatly reduced. Dust from the Sahara has on some occasions even reached Northern Europe, including Britain and Ireland, depositing yellowish dust on cars, etc..
In the Canaries the worst affected areas are usually the regions in between 1500 and 3000 feet of altitude, where it can become oppressively hot, while the lower regions benefit from a cooling effect by the Atlantic, which also supplies some moisture. The Eastern Canaries are generally more at risk. On La Gomera the phenomenon usually lasts only 2-5 days and is often followed by a shower of rain which clears the air but leaves a grimy deposit everywhere. 
The following saying is true for the Canary Islands, too: ‘When the wind is from the east, 'tis neither good for man nor beast’.
More details on the Saharan air layer

+Here's the official advice for Calima weather conditions and heat waves:

  • Carry water with you, and drink it often ! Still water is best.
  • Stay in the shade and places protected from the sun  as much as possible and/or stay cool indoors.
  • You can go for a refreshing swim, but make sure to slowly adjust to the water temperature
  • During daylight hours lower window blinds and/or close curtains and shutters.
  • Open the windows of the house at night to keep cool.
  • Use air conditioning or fans to cool the atmosphere - if unavailable, hang wet towels indoors.
  • Avoid dramatic temperature variations when entering or leaving places. Adjust gradually.
  • On the street avoid direct sunlight. Wear a cap or a hat, wear lightweight, light-colour clothing made of natural fibres, i.e. cotton.
  • Try to walk in the shade, be under an umbrella on the beach and rest frequently in a cool place.
  • Never leave children,  elderly,  pets inside a closed vehicle. 
  • Avoid prolonged physical exercise .
  • Take regular light meals,  drinks and foods rich in water and mineral salts, such as fruits and vegetables. They will help to keep you hydrated and replace the salt lost through sweating.
  • Avoid alcohol and very hot foods as well as high-calorie foods.
  • Help others. If you know of sick or elderly people living alone go to visit them regularly.
  • If you take medication, ask your doctor if it can affect thermoregulation or whether to adjust or change.

Saharan dust over Canary Islands (2004) ©earthobservatory.nasa.gov 
Normal visibility Valle Gran Rey, La Gomera
Visibility during a fairly heavy spell of CALIMA (taken Feb. 5th,2013)

2 comments :

Stan Kossen said...

I live in the Canary Islands. Normally, the weather is near-perfect. However, no place is 100 percent perfect, in my view.
Stan Kossen

Willie said...

That's right. There's a nasty easterly wind anywhere in the world every now and again.