Shamal (wind)

A shamal overspreading Iraq

A shamal (Arabic: شمال‎‎, 'north') is a northwesterly wind blowing over Iraq and the Persian Gulf states (including Saudi Arabia and Kuwait), often strong during the day, but decreasing at night.[1] This weather effect occurs anywhere from once to several times a year, mostly in summer but sometimes in winter.[1] The resulting wind typically creates large sandstorms that impact Iraq, most sand having been picked up from Jordan and Syria.


Climatology

Shamals result from strong northwest winds that are funneled into the Persian Gulf by the mountains of Turkey and Iraq to the northeast and the high plains of Saudi Arabia to the southwest. The winds most commonly are strongest in the Spring to Summer and hence the Shamal events are as well, although they can occur at any time of year. During that time of year the polar jet stream to the north moves southward to become close to the subtropical jet to the south. The proximity of the two jet streams promotes the formation of strong but often dry cold fronts which create the Shamal. The strong winds of the Shamal form in front of and behind the front. Iraq typically experiences strong wind-driven dust 20 to 50 days per year.[2]

According to folklore, the first major shamal occurring around May 25 is known as the Al-Haffar, or driller, since it drills huge depressions in desert sand dunes. The second, arriving in early June, coincides with the dawn star, Thorayya (Pleiades), and is therefore named Barih Thorayya. During this event, which is more violent than the others, fishermen usually remain in port because ancient folklore tells them that this wind devours ships. Near the end of June, the last shamal arrives, known as the Al-Dabaran, or the follower. It is violent and continues for several days. Local residents keep doors and windows firmly shut as this shamal includes an all-penetrating fine dust which gets into everything.[3]

Synoptic conditions leading to the 3-5 days Shamal

Synoptic conditions

Summer Shamal

When a passing storm with a strong cold front passes over the mountains of Turkey, the leading edge of a mass of relatively cooler air kicks up dust and sand, sending it aloft. Temperatures at lower elevations still hover above 105 °Fahrenheit (42 °Celsius) during these events.[4] In Iran, where winter storms can bring heavy snow to the terrain, a layer of dust can settle onto the snowpack.[5]

Winter Shamal

A winter Shamal is associated with the strengthening of a high pressure over the peninsula after the passage of a cold front while a deep trough of low pressure maintains itself over areas east of the Persian Gulf.[1] This leads to strong northerly wind over the Persian Gulf for periods up to five days. They are associated with cold temperatures.

The places around the Middle East most likely to see the winter variety lie near Lavan Island, Halul Island, and Ras Rakan. They persist from 24 to 36 hours during the winter and occur as frequently as two to three times per month between December and February. A persistent three- to five-day event occurs only once or twice a winter, and is accompanied by very high winds and seas.[6]

Effects

Shamals normally last three to five days. Since the resultant dust and sandstorm is several thousand feet deep, travel by air and ground comes to a standstill. When they spread to nearby bodies of water, fishing and shipping become equally difficult. During these wind events, several Southwest Asia international airports have recorded winds as high as 49 mph (43 knots) which can drive dust over large distances downwind.[7] The sandblasting effect has been reported to strip the paint off of cars .

Past example

A notable storm caused by a shamal covered Baghdad with sand on August 8, 2005, resulting in a closing of nearly all shops and public activity. The storm also overwhelmed Baghdad's Yarmuk Hospital, which treated more than a thousand people with respiratory distress.[8] From February 1 through February 4, 2008, there was a massive dust storm associated with a Shamal wind advected over the Arabian Sea. It was estimated that the leading edge of the dust storm moved at around 20 km/h, and at one point extended from Muqdisho, Somalia to Mumbai, India.[9] Dust from this storm received press from the sports media as it swept across the Dubai Desert Classic golf tournament, where Tiger Woods was playing.[10]

Some investigations have also reported that dust storms generated over west Asian regions during summer could alter regional circulation features affecting even the Indian summer monsoon rainfall.[11]

Miscellany

In Afghanistan shamal means both 'wind' and 'North.'

See also

Notes

  1. 1 2 3 El-Baz, Farouk; R.M. Makharita. Gordon and Breach Publishers, ed. The Gulf War and the Environment. pp. 31–54, 178. ISBN 2-88124-649-4. ISBN 978-2-88449-100-6. Retrieved 2009-06-03.
  2. ↑ DUST STORMS, SAND STORMS AND RELATED NOAA ACTIVITIES IN THE MIDDLE EAST. Retrieved on 2008-07-21.
  3. ↑ DataDubai. Climate: March 16 2006. Retrieved on 2006-12-09.
  4. ↑ Weather Corner: Desert wind pattern in Iraq to shift in next two months. Retrieved on 2006-12-09.
  5. ↑ NASA Earth Observatory. Natural Hazards >> Dust & Smoke >> Shamal Winds Drive Middle East Dust Storm. Retrieved on 2006-12-09.
  6. ↑ United States Navy. Appendix C: Wind Climatology of the Winter Shamal. Retrieved on 2006-12-09.
  7. ↑ NOAA Magazine. DUST STORMS, SAND STORMS AND RELATED NOAA ACTIVITIES IN THE MIDDLE EAST. Retrieved on 2006-12-09.
  8. ↑ NASA Earth Observatory. New Images: Iraq Dust Storm. Retrieved on 2006-12-09.
  9. ↑ Arabian Sea dust storm AVHRR images from Amato Evan website .
  10. ↑ Tiger Woods Battles Sand Storm to Lead at Dubai Desert Classic .
  11. ↑ http://www.nature.com/ngeo/journal/v7/n4/full/ngeo2107.html
  12. ↑ CNN. AMERICAN MORNING: Interview With National Geographic Bee Champion. Retrieved on 2006-12-09.

External links

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