مقياس بوفورت

درجة قوة 12 في البحر.

مقياس بوفرت Beaufort scale (تـُنطـَق /ˈboʊfərt/) هوقياس empirical لوصف سرعة الريح مبنياً في الأساس على أحوال البحر الإشارة. اسمه الكامل هومقياس بوفرت لقوة الريح Beaufort wind force scale.

التاريخ

طور المقياس عام 1805 السير فرانسيس بوفرت، الأميرال والرسام البحري البريطاني الأيرلندي المولد.

المقياس يتألف من سلسلة من الأعداد من صفر إلى 17. ويستعمل للإشارة إلى سرعات الرياح. وقد صَمَّمَ هذا المقياس في عام 1805م العميد البحري البريطاني فرانسيس بوفورت. وقد حدد بوفورت مفهوم هذه الأعداد، وبخاصة تأثير الرياح المتنوعة على السفن الشراعية. ففي نص نموذجي ـ ويقدم هنا على سبيل المثال ـ نُشر في عام 1874م، يقرر المقياس حتى الرقم 2 يشير إلى رياح فسَّرها على النحوالتالي: رياح يمكن لبارجة مُجَهَزَّة بكل معدات الإبحار، وفي حالة جيدة، ومفرَّغة ـ تماماً ـ حتى تبحر في مياه هادئة وصافية بسرعة من عقدة إلى عقدتين. أمَّا الرياح التي يرمز إليها الرقم 12 فهي تلك الرياح التي لايمكن حتى يَصمد أمام قوتها أي شراع. وفي الوقت الحاضر يمكن تحديد مفهوم مقياس بوفورت الخاص بسرعات الرياح، والتي يمكن قياسها في نطاق 10م فوق سطح الأرض، كما يُستعمل هذا المقياس أحياناً في تقدير سرعات الرياح.

Wind speed on the 1946 Beaufort scale is based on the empirical formula:

v = 0.836 B^3/2m/s

حيث v is the equivalent wind speed atعشرة meters above the sea surface and B is Beaufort scale number. For example, B = 9.5 is related to 24.5 m/s which is equal to the lower limit of "10 Beaufort". Using this formula the highest winds in hurricanes would be 23 in the scale.

Note that wave heights in the scale are for conditions in the open ocean, not along the shore.

المقياس العصري

Beaufort number	Description	Wind speed				Wave height		Sea conditions	Land conditions	Sea state photo
Beaufort number	Description	km/h	mph	kts	m/s	m	ft	Sea conditions	Land conditions	Sea state photo
0	Calm	< 1	< 1	< 1	< 0.3	0	0	Flat.	Calm. Smoke rises vertically.
1	Light air	1 – 5	1 – 3	1 – 2	0.3 – 1.5	0 – 0.2	0 – 1	Ripples without crests.	Wind motion visible in smoke.
2	Light breeze	6 – 11	4 – 7	3 – 6	1.5 – 3.3	0.2 – 0.5	1 – 2	Small wavelets. Crests of glassy appearance, not breaking	Wind felt on exposed skin. Leaves rustle.
3	Gentle breeze	12 – 19	8 – 12	7 – 10	3.3 – 5.5	0.5 – 1	2 – 3.5	Large wavelets. Crests begin to break; scattered whitecaps	Leaves and smaller twigs in constant motion.
4	Moderate breeze	20 – 28	13 – 17	11 – 15	5.5 – 8.0	1 – 2	3.5 – 6	Small waves with breaking crests. Fairly frequent white horses.	Dust and loose paper raised. Small branches begin to move.
5	Fresh breeze	29 – 38	18 – 24	16 – 20	8.0 – 11	2 – 3	6 – 9	Moderate waves of some length. Many white horses. Small amounts of spray.	Branches of a moderate size move. Small trees begin to sway.
6	Strong breeze	39 – 49	25 – 30	21 – 26	11 – 14	3 – 4	9 – 13	Long waves begin to form. White foam crests are very frequent. Some airborne spray is present.	Large branches in motion. Whistling heard in overhead wires. Umbrella use becomes difficult. Empty plastic garbage cans tip over.
7	High wind, Moderate gale, Near gale	50 – 61	31 – 38	27 – 33	14 – 17	4 – 5.5	13 – 19	Sea heaps up. Some foam from breaking waves is blown into streaks along wind direction. Moderate amounts of airborne spray.	Whole trees in motion. Effort needed to walk against the wind. Swaying of skyscrapers may be felt, especially by people on upper floors.
8	Gale, Fresh gale	62 – 74	39 – 46	34 – 40	17 – 20	5.5 – 7.5	18 – 25	Moderately high waves with breaking crests forming spindrift. Well-marked streaks of foam are blown along wind direction. Considerable airborne spray.	Some twigs broken from trees. Cars veer on road. Progress on foot is seriously impeded.
9	Strong gale	75 – 88	47 – 54	41 – 47	21 – 24	7 – 10	23 – 32	High waves whose crests sometimes roll over. Dense foam is blown along wind direction. Large amounts of airborne spray may begin to reduce visibility.	Some branches break off trees, and some small trees blow over. Construction/temporary signs and barricades blow over. Damage to circus tents and canopies.
10	Storm, Whole gale	89 – 102	55 – 63	48 – 55	25 – 28	9 – 12.5	29 – 41	Very high waves with overhanging crests. Large patches of foam from wave crests give the sea a white appearance. Considerable tumbling of waves with heavy impact. Large amounts of airborne spray reduce visibility.	Trees are broken off or uprooted, saplings bent and deformed. Poorly attached asphalt shingles and shingles in poor condition peel off roofs.
11	Violent storm	103 – 117	64 – 72	56 – 63	29 – 32	11.5 – 16	37 – 52	Exceptionally high waves. Very large patches of foam, driven before the wind, cover much of the sea surface. Very large amounts of airborne spray severely reduce visibility.	Widespread damage to vegetation. Many roofing surfaces are damaged; asphalt tiles that have curled up and/or fractured due to age may break away completely.
12	Hurricane	≥ 118	≥ 73	≥ 64	≥ 33	≥ 14	≥ 46	Huge waves. Sea is completely white with foam and spray. Air is filled with driving spray, greatly reducing visibility.	Very widespread damage to vegetation. Some windows may break; mobile homes and poorly constructed sheds and barns are damaged. Debris may be hurled about.

انظر أيضاً

American Practical Navigator
Saffir-Simpson Hurricane Scale
Douglas Sea Scale
Enhanced Fujita Scale
Fujita scale
TORRO scale
CLIWOC
Sea state

الهامش

Huler, Scott (2004). Defining the Wind: The Beaufort Scale, and How a 19th-Century Admiral Turned Science into Poetry. Crown. ISBN .

^ Tom Beer (1997). . CRC Press. ISBN .
^ The names "storm" and "hurricane" on the Beaufort scale refer only to wind strength, and do not necessarily mean that other severe weather (for instance, a thunderstorm or tropical cyclone) is present. To avoid confusion, strong wind warnings will often speak of e.g. "hurricane-force winds".

وصلات خارجية

UK Meteorological Office: The Beaufort Scale
Investigating Clouds, a lesson plan from the National Science Digital Library that uses the Beaufort Scale.
Radio interview with Scott Huler.
OceanWeather.com gives current graphics for wind, waves and temperature
Open Source Textbook at Oceanworld.tamu.edu cites the original definition formula in chapter 4
Howtoons Poster showing effects on land/sea effects at each step.
US Economic Costs of High Winds NOAA Economics
Online calculator: Beaufort scale
The Weather Legacy of Francis Beaufort — The history of the Beaufort Scale.
Ireland's Beaufort was Windscale Inventor - by Dr John de Courcy Ireland