Sand and dust storms (SDS) appears to be growing in number and severity in Iran over the past several decades. This is largely due to the lack of attention to preservation and protection of the environment, as well as the destruction of renewable natural resources. Dust storms are also increasingly occurring in areas where they haven’t in the past. They have more than doubled in parts of the northeastern and northwestern provinces, and particularly in East Azerbaijan, West Azerbaijan, and Kurdistan (1, 2).
Kutiel and Furman pointed out that a positive correlation exists between the quantity of dust in the air and the wind velocity, whereas a negative correlation exists between dust amount and the particles’ size. Precipitation and/or vegetation coverage may reduce considerably the amount of dust in the air for a given wind velocity and/or particle size. Thus, a study of the atmospheric circulation and its impact on the precipitation level of a given region is crucial to understand the dust distribution in that region (3).
These increases run parallel with regional changes in climate as well. Much of Iran has increasingly become arid over the past half century due to bad grazing practices and increased livestock numbers beyond pasture tolerance. According to Iran’s Second National Communication to the United Nations Framework Convention on Climate Change, average temperatures have consequently increased by nine degrees Fahrenheit (five degrees Celsius) since 1960, while annual rainfall has dropped across much of the country (4). Furthermore, global warming could certainly exacerbate these trends. Iranian studies have projected that average temperatures could climb almost two degrees (about one degree Celsius) by 2039, while precipitation across the country could drop by 9 percent. A hotter, more arid climate would further dry the soil, creating more loose dust and sand to be swept away by wind (5). However, climatic pressures are by no means the only driving force behind Iran’s dust storms. Iranian agricultural, land, and water management policies substantially aggravate the environmental stresses that worsen dusty conditions (6).
Now, what are the locations of particulate sources carried in dust storms to Iran? There are some endemic sources and some that lay beyond Iran’s borders (1). West Asia, especially the Tigris–Euphrates alluvial plain, is suffering from severe desertification caused by climate change and other human-induced factors, such as mismanagement of land use, cultivation, overgrazing, marginal plowing and years of warfare (7).
In 1991 and again in 2003, the southern part of Iraq suffered from very large military actions. Thousands of heavy trucks and crawling military vehicles; of different types and sizes that attain more than 30 tons, crossed the southern parts of Iran, often driving offroad. The use of wheeled trucks and crawlers, as well the explosion of enormous amounts of bombs and rockets of different sizes, have destroyed the compacted top soil layer in large areas causing emission of dust and facilitating in development of dust and/or sand storms. This area has been recognized as one of the most important SDS source areas in the world (8).
An analysis of the predicted climate change scenarios portrays a harsher situation for the West Asia region in the coming years. Whether in the form of desertification, deforestation, or wetland destruction, or by the effects of population growth, food insecurity or water shortage, the countries in the region are expected to experience catastrophic environmental and socio-ecological events more than ever before. Most of the countries in the region are now experiencing frequent sand and dust storms as a result of destructive ecological footprints (9).
Dust sources, regardless of size or strength, can usually be associated with topographical lows located in arid regions with annual rainfall under 200- 250 mm. Iran, Iraq, Jordan, the southern part of Turkey, Saudi Arabia, Kuwait and Syria are the main sources of the dust storms of Iran; these countries have arid and semiarid climate and are located in the Dust Belt. However, the Middle East is well known for its arid and semi-arid environment with frequent and severe dust and sand storms. Of all the world’s regions, only Africa has a more severe dust problem than the Dust Belt (11).
Due to Iran’s geographical situation and topographical features, about 80% of Iran’ s total area experiences an arid or semiarid climate. There are, however, variations in reports on the quantity of desert areas in Iran due to differing definitions; some estimates have showed that, at present, the land area of desert and sand-covered regions is estimated to be 34 million hectares (5 million active and 12 million inactive sands, whereas the remaining areas are salt-accumulation lands, saline and alkaline soils, gravelly lands, etc.); that of the poor and bare rangelands is 16 million, together reaching about 50 million hectares (12).
There is an urgent need to identify the SDS sources in West Asia, and to then respond accordingly to find efficient solutions in combatting sand and dust storms. Some research has provided direct or indirect proof of SDS source areas in Iraq and eastern part of Syria, mainly located in the Tigris–Euphrates plain while for Jordan, Iran and Saudi Arabia, only indirect clues such as vegetation types, bioclimatic zone and land use have been considered for investigation of sand sources. However, sand and dust storms result from various factors and thus any investigation necessitates incorporating multiple technologies and information to refine SDS hotspots (9). Some research has also indicated that the origin of the dust that enters Iran comes from Saudi Arabia, and the north and northwest part of Iraq at Syria’s borders (13).
Main SDS source areas are located in the southeastern part of Syria, which has a land area of 36,583 km2. The soil type of SDS source areas in Syria is fine dry gypsum and calcite that covers roughly 20% of the country. These soils contain high concentrations of gypsum, ranging from 70% to 95% in extreme cases. They dominate the central and southern parts of Mesopotamia, including the Euphrates and Khabour terraces, the northern part of the Syrian Desert and a large part of the Bichri Mountains. The area located above the Euphrates River is mainly covered by gypsum-containing soils as well. Calcite soil types are generally distributed in the Syrian section of the Hamad Plateau and the southeastern part of the Syrian Desert.
Observing the long sand strips
All SDS source areas suffer from strong wind erosion; by determining wind direction, these become easily identifiable. Syria’s coastal and northern areas are under the influence of the Mediterranean Sea climate, while the southern section is part of a tropical desert climatic zone. The Syrian Desert thus receives the dominating wind rising from east of the Mediterranean Sea, over Cyprus, extending deep into southeastern Syria and Iraq. They are major sources of SDS in Syria. In these areas, thick layers of loose tertiary sands are the source material for alluvial sediments. The dominant winds blowing from southwestern Syria to the northeast mainly originate from coastal areas in North Africa. It makes all parts of the Syrian Desert SDS source areas (14).
Different studies have also revealed that the Tigris and Euphrates Basin is another dust storm source because of human-related activities. The area has great potential for generating dust. This basin’s bedrock is made of soft neogene deposits. The other origins of dust are particulates of igneous rocks, deposited within the clay beds of the Tigris and Euphrates Basin (15).
Deserts cover the majority of Iraq’s landscape, especially it its west. Sand dunes are located in several parts of these regions, mainly to the west of the Euphrates River. The texture of these hills alter from loom to sand with small to average sizes, and the potential of their erosion has been calculated to be 230,000,000 square meters (12, 13).
They can thus be carried by wind toward Iran and there become a source of dust storms. Analysis of existing research has revealed that the dust originating from the north and northwest of Iraq and northeast of Syria travels to the west and southwest of Iran. Based on the Middle East’s geological condition and high level of dust generation, it is expected that the origin of the dusts in the western and southwestern parts of Iran is one of those regions that have a dust-generating background (15).
The geological map of Iraq and Syria indicates that the bedrock around the Tigris and Euphrates rivers are composed of soft Neocene deposits from late Miocene. The constituent material of most of the deposits around the northern section of the Arabian plate is sedimentary, and originated mostly from shells, Jurassic sandstones, cretaceous limestone, Marni limes, and shells dating from the Paleocene to the Miocene. These young and unstable deposits are very vulnerable against erosive factors such as rain and wind. Particulates of these sedimentary rock layers have been carried into low places by wind, rivers, creeks and flooding. In the past, some of these low-lying grounds were irrigated by the Tigris and Euphrates, creating prosperous agriculture in these areas. Decreasing water and vegetation, as well as human activity, has caused the land to become bare and its surface easily eroded. However, lack of rain in this region and the inner regions of the Saudi Arabian Peninsula has caused an arid region consisting of sand, clay and silt which has potential of generating dust storms that moves toward the western and southwestern parts of Iran (16).
There is an urgent need to identify the SDS sources in West Asia in order to find an efficient method to combat sand and dust storms. There is abundant research providing direct proof of the presence of SDS source areas in Iraq and eastern Syria, mainly in the Tigris–Euphrates plain, while in Jordan, Saudi Arabia and Iran, only indirect clues such as vegetation types, bioclimatic zone and land use have been considered as sand sources.
The seasonal variation of dust activity in the Middle East is complex and differs for different regions. Over much of the Middle East, dust is active all year long, but it decreases in the winter months. Dust activity increases in March and April, peaks in June and July and weakens in September (17).
In West Asia, most of dust storm systems can be classified into Sum- mer Shamal and Frontal dust storms. Shamal dust storms usually occur across Iraq, Kuwait, the western Khuzestan plains and some parts of Arabian Peninsula. Summer shamal is basically generated by a convergence zone between the subtropical ridge, extending into the northern Arabian Peninsula and Iraq from the Mediterranean Sea and monsoons through much of southern Iran and the southern Arabian Peninsula (18).
The most important reason for the occurrence of dust storms in Iraq is the passage of a low-pressure system over Iran that carries cool air from that region towards warmer regions with warmer air, like eastern Syria and Iraq. In some cases, this low-pressure system is followed by a high-pressure system bringing more cold air to the region and pushing dust toward the south. During winter and spring, dust storms are often associated with the formation of clouds in nearby areas. Dust and clouds are formed by the same meteorological phenomena (19).
Frontal dust storms are dynamic synoptic systems that mix dust in the air and carry it along greater distances in non-summer seasons. There are three types of frontal dust storms: prefrontal, postfrontal and shear-line. Pre- frontal dust storms occur across Jordan, Israel, the northern Arabian Peninsula, Iraq and western Khuzestan Plains of Iran as low-pressure areas move across the region. Postfrontal dust storms are referred to as “winter Shamal” across most of Middle East. Shear-lines are the result of the convergence of northeasterly wind flows to the south of a polar high-pressure cell and the easterly trade-wind flow (20).
SDS source clusters and main paths are generated according to the features of SDS source areas climate and geography, and knowledge from historical studies. The main SDS paths dominated by the climate in West Asia are as following (2):
(1) The first path originates from Mediterranean Sea passing over Cyprus and enters into Syria. It turns to the southeast through the Syria–Iraq border and extends into central Iraq. Commonly, this path will go further south of Iraq, Kuwait and the Persian Gulf. While crossing with other streams, it usually has alternative destinations. One moves toward southern Iraq and Saudi Arabia through the southern border of Iraq and Saudi Arabia. The other one turns right, across the Iraq–Iran border and terminates in Iran.
(2) The second path is under the control of high-pressure systems over Eastern Europe. This path shares a similar situation with the first one, which has two common branches. When arriving in central Iraq through the northern border, it either hits Iran through the Iraq–Iran border, or goes east of Saudi Arabia, then south of the Iraq-Kuwait border.
Wind erosion is common in arid and semi-arid regions. Impacts are largely assessed based on their on-site effects on soils or off-site effects like air pollution. The role of wind erosion in global biological cycles, especially its impact over time, has received comparatively little attention, despite the large amount of nutrients that are transferred by wind erosion. The wind erosion process detaches soil particles from the land surface and transports them far away. It occurs when forces applied by wind overcome the gravitational and cohesive forces of soil particles on the surface of the ground.
This phenomenon is one of the natural disasters common to all arid regions. Central Iran is increasingly troubled by mismanagement of natural resources, and the rise of this phenomenon has had a large impact. Precipitation, temperature and wind are the most important climatic factors that affect wind erosion. Iran is located in a universal desertification and wind erosion belt so that a substantial part of its area experiences a dry climate. Wind erosion is a serious challenge for sustainable production and agricultural land management. One of the most important tools in the development of a country is identifying resources, hurdles of different climatic conditions, and then planning accordingly.
Erosion is usually due to lack of reasonable management practices of soil and land, such as poor agricultural practices, overgrazing, deforestation, and other abuses of renewable natural resources. The aforementioned practices degrade adhesion properties of soil and make the natural habitats vulnerable to wind erosion. Such acts slowly cause fine particles of soil to increase and gradually elevate sand particles that don’t have adhesion to the ground and are therefore vulnerable to wind transport. Strong winds will lift and move sand and soil particles. The repeated removal of superficial layers by the action of winds can modify the texture of the topsoil, by removing the fine particles and leaving the larger particles.
Research indicates that dust originating from the north and northwest of Iraq and the northeast of Syria enters into the west and southwest of Iran. However, the lack of attention paid by countries in the Middle East must not be dismissed. In order to respond to such a huge challenge, cooperation of all countries in the region is a must.
1. JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 117, D03201, doi:10.1029/2011JD016339, 2012
2. Boloorani et al. Journal of Environmental Health Science & Engineering 2014, 12:124 http://www.ijehse.com/content/12/1/124
3. Kutiel, H. & Furman, H., 2003. Dust Storms in the Middle East: Sources of Origin and their Temporal Characteristics. Indoor Built Environ, 12, 419–426
6. http://profdoc.um.ac.ir/articles/a/1019133.pdf2. J Nov. Appl Sci., 3 (10): 1131-1136, 2014
7. H. Cao et al. / Science of the Total Environment 502 (2015) 224–235
8. V. K. Sissakian et al. / Natural Science 5 (2013) 1084-1094
9. Atmospheric and Climate Sciences, 2013, 3, 321-336
http://dx.doi.org/10.4236/acs.2013.33034 Published Online July 2013 (http://www.scirp.org/journal/acs)
10. Iran s 4th National Report to CBD- Final- Oct 2010
11. Carpathian Journal of Earth and Environmental Sciences, February 2011, Vol. 6, No. 1, p. 297 – 308
17. Asia-Pacific J. Atmos. Sci., 49(3), 279-286, 2013
19 International Journal of Energy and Environment (IJEE), Volume 4, Issue 5, 2013, pp.851-858