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Atlas of Jordan

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Myriam Ababsa

Chapter one - Constraints and Resources

Aridity

Myriam Ababsa

Texte intégral

1“The main characteristics of Jordan’s climate reflect the transnational location of the country between the Mediterranean climate in the west and the arid climate in the east and the south” (RJGC 1984). The Mediterranean climate prevails in the Highlands region, where summer is moderate and dry and the winter cold and rainy. The desert climate prevails in the Badiya; the summer is hot and the winter is cold. The Ghor area has a semitropical climate with a hot summer and warm winter.

2Depressions, mostly of Mediterranean origin, start affecting Jordan in mid-October and dominate the weather until late April. December and January depressions are frequently accompanied by polar air masses of north European origin. In summer, which is the most stable season, a huge belt of low pressure forms over North Africa and extends through the Arabian and Indian Oceans to India. This low-pressure belt attracts hot and dry northerly continental tropical air masses from the high-pressure centres over Mesopotamia and Asia Minor. Spring and autumn are the two transitional seasons in Jordan. Spring depressions are called ‘Khamsin depressions’ or ‘Saharian depressions’.

Rainfall

3Jordan is an arid country with more than 90 percent of the territory receiving less than 200 mm annual precipitation.

4Precipitation ranges between 50 to 500 mm annually, depending on the location. The amount of rainfall decreases from north to south and from west to east. The annual average in the eastern heights, in the Ajlun Mountains, reaches 400-600 mm, then decreases to 300-600 mm in the Balqa’ mountains, 200-350 mm in the Moab mountains, and 100-300 mm in the Sharah mountains. The annual average in the northern part of the rift reaches 300-400 mm but drops to 100-200 mm north of the Dead Sea and 50-100 mm in the Dead Sea area north of Wadi Araba. The southern part ofWadi Araba and the Gulf of Aqaba receive less than 50 mm. Rainfall varies from year to year, while occasional light snowfall is restricted to the highest areas (including Amman) (table I.1, fig. I.12).

Figure I.12 — Jordan Average Rainfall.

Figure I.12 — Jordan Average Rainfall.

MWI - GTZ 1977

Table I.1Rainfall distribution in Jordan.

Rainfall range (mm)

Area (ha)

% of total area

< 50

3 679 670

41.26

50–100

2 325 260

26.07

100–200

1 986 630

22.28

200–300

435 700

4.89

300–400

216 210

2.42

400–500

118 030

1.32

> 500

104 520

1.17

Dead Sea

52 990

0.59

Total

8 919 010

100

(Jaloudy 2006)

 

 

Average Temperatures

5Average temperatures show a reverse pattern; they increase rapidly from the dissected plateaus to the very low level graben, increase gradually from the dissected plateau to the eastern margins of the eastern desert, and decrease gradually from north to south in line with increasing altitude. The range of average annual temperatures is 22°C to 25°C in the Jordan Rift area, 18°C to 21°C in the Badiya, and 14°C to 18°C in the highlands.

6The country’s long summer reaches a peak during August. January is usually the coolest month. The fairly wide ranges and differences in temperature during a twenty-four-hour period are greatest during the summer months and have a tendency to increase with higher elevation and distance from the Mediterranean coast.

Winds

7“For a month or so before and after the dry summer season, hot, dry air from the desert, drawn by low pressure, produces strong winds from the south or southeast that sometimes reach gale force. Known in the Middle East by various names, including the Khamsin, this dry, sirocco-style wind is usually accompanied by great dust clouds. Its onset is heralded by a hazy sky, a falling barometer, and a drop in relative humidity to about 10 percent. Within a few hours there may be a 10°C to 15°C rise in temperature. These windstorms usually last a day or so, cause much discomfort, and destroy crops by desiccating them” (RJGC 1984).

8The shammal, another wind of some significance, comes from the north or northwest, generally at intervals between June and September. Remarkably steady during daytime hours but becoming a breeze at night, the shammal may blow for as long as nine days out of ten and then repeat the process. It originates as a dry continental mass of polar air that is warmed as it passes over the Eurasian landmass. The dryness allows intense heating of the earth’s surface by the sun, resulting in high daytime temperatures that moderate after sunset (fig. I.13).

Figure I.13 — Climographs of three meteorological stations.

Figure I.13 — Climographs of three meteorological stations.

GTZ 2004

Table des illustrations

Titre Figure I.12 — Jordan Average Rainfall.
Crédits MWI - GTZ 1977
URL http://books.openedition.org/ifpo/docannexe/image/4865/img-1.jpg
Fichier image/jpeg, 144k
Titre Figure I.13 — Climographs of three meteorological stations.
Crédits GTZ 2004
URL http://books.openedition.org/ifpo/docannexe/image/4865/img-2.jpg
Fichier image/jpeg, 128k

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