By Dr. M. Badarch, Dr. L. Natsagdorj, Mongolia Dust and sand storm and desertification process in Mongolia Geographic and climate condition of Mongolia Mongolia is a landlocked country of 1.56 m sq. km (six times the size of Japan), located between Russia and China. The average elevation of 1,580 metres, its location in the northern hemisphere high pressure belt, and it being east and south of high mountain chains in the middle of the Asian Continent, make Mongolia’s climate cool and dry. There are six different ecotones from the high alpine and inter-montane lake area in the west, through taiga forest, forest steppe, steppe, desert steppe and desert, proceeding south and SE. The vegetation is sparse throughout the land, as is the human population density (at a national average of about 1.5 persons per sq. km). The climate is harsh continental, with long, cold, dry winters and short, hot, dry summers. Sixty years of meteorological records show that the annual average temperature is around 8.5 0C in the Gobi Desert and minus 7.8 0C in the high mountains, and that the average annual precipitation in those areas is less than 220mm and 400mm respectively. Droughts are frequent, on a cycle of approximately 1 year in 5 in the Gobi and 1 year in 10 in the mountain areas. The same 60-year data shows that the national average temperature increased by 1.56 0C over the same period, the greatest increases (3.6 0C) being recorded during winter in the mountainous west.( source: Mongolia Environment monitor, World Bank, 2000l) The total water resource in Mongolia is about 599 cubic km: 83.7% in large lakes located in the inter-mountain basins of the Altai, Khuvsgul, Khentein and Khangai mountain region, 10.5% in glaciers and 5.8% in rivers. But little water is available on a renewable basis. The annual average precipitation of only 224 mm (90.1 percent of which evaporates) varies widely from year to year and from one part of the country to another. An average precipitation of 250mm/year. There is evidence that lakes and rivers have diminished in volume over recent years. Reasons for this include climate change, deforestation, irrigation and agriculture, mining and land degradation (mostly due to adverse human activities) Surface and ground water levels have dropped. Aggravated desertification, salinization and poor water quality are major problems in the arid and semi-arid regions.
Ecological factors contributing to dust and sand storm (DSS)
Mongolian scientists conducted the research on distribution of dust storm days of central Asia the results of which shows in Fig.1. It shows that dust storm reached from 20 to 30 days in territory of Mongolia and some part of inner Mongolia , China. Atmospheric circulation and
dangerous weather phenomenon over the territory of Mongolia. ( source: Publication of HydroMeteorological Research Institute of Mongolia, No. 6, Ulaanbaatar, pp. 300.)
Figure 1. Number of days with dust storms in Central Asia Number of dustydays and trends It is clear that dust storms occur at places with less vegetation cover, dry and loose sandy (dusty) soil, when wind speed reaches a certain value; 8 ms -1 . both dust storms and drifting dust have an important effect on soil erosion. Therefore, we are able to estimate, where desertification process takes place, by using the number of dusty days recorded over many years.Mongolian scientists derived the number of dusty days per year from sum of the number of days with dust storms and drifting dust obtained from 34 meteorogical stations in Mongolia from 1960 to 1999 (Fig 2.).
Fig.2. Number of dusty days in Mongolia and its trend It can be seen in fig 2 that the number of dusty days was about 15 days in the 1960’s and about 50 days in the 1980’s, an increasing of more than 3 times. Nevertheless, the number of dusty days may be linked to human activity and the amount of annual precipitation. Since 1960s, populated areas increased, the number of transport means such as lorry, truck, tractor increased. The natural pasturelands overgrazed, and soil erosion considerably took place due to increasing of cultivated land area near setllements. Moreover, the amount of annual precipitation has “decreased” since mid 1960s until 1980s when compared to the end of 1950s. In addition, the driest period was in the 1980s ( source: D., Dagvadorj, L., Natsagdorj. D., Gomgluudev, Natsagdorj, P.,1999. Climate change and its trend in Mongolia. Scientific report of Institute of Meteorology an Hydrology et al., 1999), Ulaanbaatar, No.20, pp.115-133).
Annual amount of precipitation
Number of dusty days
Fig . 3. Annual amount of precipitation and dusty days in Mongolia According to Fig. 3, annual amount of precipitation and dusty days have a reverse correlation and they coincided well negatively. In the last 10 years, particularly since 1990-1994, annual precipitation has increased and its trend has a slight increase while dusty days has dropped down with a decreasing trend in Mongolia. This may be the cause of dusty days decreasing in the last 10 years. Other explanations must be sought to clear up uncertainty by a further study. Annual and daily regimes of dust storms Clearly, there is an annual variation in dust storm occurrences in Mongolia. In association with the movement of the middle-latitudinal cold frontal belt, the highest frequency (61%) of dust storms occurs in spring and second maximum frequency occurs in autumn (October and November) in Mongolia. The annual minimum frequency (7%) occurs in summer, in which a low-pressure field with small pressure gradient predominates, and (10%) in winter, in which cyclonic activity is weak and the air is most stable. Annual variations in dust storm occurrences in the Gobi (station Dalanzadgad), steppe (station Baruun-Urt), and mountainous regions (station Muren) are shown in Fig. 4, and we include the number of days with dust storms on representative selected stations in the three different geographical regions.
5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 1 2 3 4 5 6 7 8 9 10 11 12
Fig. 4. The annual regimes of dust storms (number of days with dust storms). N- number of days with dust storms; St.373-Dalanzadgad station ; St.305-Baruun-Urt station ; St.231-Muren station. The annual regime of dust storm is significantly variable at the different stations. For example, with respect to geographical condition, dust storm occurrences in winter not appear in the Uvs Lake hollow, but its frequency is 28.5% at the Bulgan Soum (the Saikhan station) of Umnigobi Aimag ( Source: Natsagdorj, L., 1982: Atmospheric circulation and dangerous weather
phenomenon over the territory of Mongolia. Publication of Hydro-Meteorological Research Institute of Mongolia, No. 6, Ulaanbaatar, pp. 300). Dust storms have a clear daily regime in the Gobi and the steppe area in Mongolia. The daily variation increases in daytime and decreases in nighttime. In daytime, the heating of the ground surface produces wind and unstable conditions of the air and in nighttime, the opposite occurs. In order to clarify daily regime of dust storms, we obtained their frequency at every three hours in spring, autumn and winter in the Gobi and steppe regions (Table 1). The daily regime of dust storms for spring in the Gobi is shown in Fig. 5. The frequencies of both dust storms and drifting dust are highest between 1200 O’clock and 1800 O’clock and it does not depend on geographical region or season.
Table 1. Daily regime of dust storms (frequency %). Type Area Season 0-3 8.7 5.2 6.4 4.0 3.0 2.0 8.9 5.6 6.5 2.0 1.7 1.0 3-6 9.4 5.0 6.0 2.0 2.7 2.0 8.6 5.5 6.9 1.0 1.7 2.0 Time interval (hours) 6-9 9-12 121515 18 7.1 13.0 19.9 20.4 6.5 12.9 20.3 23.8 7.7 13.9 21.9 24.3 4.9 7.4 5.1 9.9 6.4 7.7 4.0 7.7 6.0 25.7 16.7 22.2 16.2 16.3 15.9 25.0 19.7 24.0 32.7 25.1 28.3 21.5 23.3 22.9 36.0 29.8 34.0 20.8 25.4 24.3 18.3 22.7 22.7 23.0 25.7 25.0
Gobi Dust storm
Winter Spring Autum n Winter Steppe Spring Autum n Winter Gobi Spring Autum n Winter Steppe Spring Autum n
1821 13.9 18.6 12.7 0.9 15.0 10.1 9.3 14.8 10.7 7.0 11.4 6.0
2124 8.5 7.7 7.0 3.0 4.7 4.0 7.1 5.3 6.5 2.0 2.3 2.0
25 20 15 10 5 0
0-3 3,1-6 6,1-9 9,1-12 12,1-15 15,1-18 18,1-21 21,1-24
Time interval (hours)
Fig. 5. The daily regime of dust storms for spring in the Gobi.
Duration of dust storms For a study of the duration of dust storms, the researchers we used data obtained from 1975 to 1999. Monthly mean and annual mean duration of dust storms and drifting dust in the Gobi and the steppe area in Mongolia coincided well with their frequencies. Where frequency is high there is a longer period of dust storms. Annual mean duration of dust storms is greater than 100 hours over the Gobi on the south of the Altai Mountain and the territory of Omnogobi Aimag , for example, about 364 hours at the Saikhan station in this Aimag. However, the maximum length of drifting dust is about 485 hours around the Mongol Els area.
Duration of dusty days is longer than 200 hours per year over the Gobi on the south of the Altai Mountain, Umnigobi Aimag and around the Mongol Els area. For example, it is about 493 hours at the Tooroi station in the south of the Altai Mountain, about 614 hours at the Saikhan station of Umnigobi Aimag, and about 508 hours at the Durvuljin station near the Mongol Els area. In order to determine the average duration of a dust storm occurrence, first we determined the duration of dust storm occurrences over 15 years (10458 hours in the Zamiin-Uud). After that, the figure was divided by the total number of dust storm occurrence over the 15 years (233 cases over 15 years in Zamiin-Uud ). In this way, we also obtained the average duration of dust storm occurrence at other stations in the Gobi (Table 2. ).
Figure 6 shows the average duration of a dust storm. Table. 2.. Average duration in a dust storm (a drifting dust) occurrence (hours). Station DS Baitag 3.5 Tooroi 4.0 Ekhiin gol 7.1 Tonkhil 4.6 Altai 3.3 Gurvantes 6.2 Saikhan 8.5 Tsogt-Ovooî 5.4 DS-dust storm; DD-drifting dust DD 3.4 3.1 5.4 4.8 3.3 4.8 4.6 3.0 Station Dalanzadgad Khanbogd Bogd Saikhan-Ovoo Mandalgobi Choir Sainshand Zamiin-Uud DS 4.6 4.1 2.9 2.8 3.9 5.3 3.3 4.7 DD 3.2 3.0 3.6 2.4 2.4 4.6 2.1 4.3
A dust storm (also a drifting dust) lasts in average from 1.6 to 6.0 hours, sometimes more than 12 hours in the Gobi and less than 3 hours (60%-80%) in the mountainous area. If the average duration of a dust storm (also a drifting dust) occurrence is more than 6 hours then its frequency decreases. This is shown for the Gobi in Fig.6. and for the mountainous areas in Fig. 7. The duration of a dust storm occurrence is longer in spring and shorter in summer.
40 35 30 25 20 15 10 5 0
<1 1,1-3 3,1-6 6,1-9 9,1-12 12,1-15 15,1-18 18,1-21 21,1-24 24,1<
Time interval, hours St.325 St.374 St.358
Fig.6. Average duration of a dust storm occurrence in the Gobi.
St.325-Tooroi station; St.374-Gurvantes station; St.358-Zamiin-Uud station.
90 80 70 60 50 40 30 20 10 0 <1 1,1-3 3,1-6 6,1-9 9,1-12 12,1-15
Time interval, hours St.272 St.282 St.241
Fig. 7. Average duration (time interval) of a dust storm occurrence in the mountainous area. St.272-Uliastai station; St.282-Tsetserleg station; St.241-Baruunharaa station(focus area). 2. Root Causes of Dust and sand storm(DSS) ( Drivers of changes and contribute to increasing dust and sand storm in Mongolia) Climate Change The climate of Mongolia contributing to DSS. It is a cold, dry land subject to dust storm events. Climate change threatens to aggravate drought, heavy winds and further reduce or limit human socio-economic activities, and cause an increase in the frequency of storms, e.g., dust storms and dzuds (very cold winter snow storms). Mongolia’s vulnerability to these climatic events is well known. However, the strong DSS in summer that followed very dry summers (with limited plant growth) usually seriously impacted the pastoral economy, society and the environment and brought to the fore the country’s vulnerability to its climate and environment, and to their change -- with potentially wide impacts on ecological and socio-economic systems alike. Mongolian researchers identified several related adaptation measures specifically to cope with climate change in Mongolia. Measures included those to: ( source: Mongolia, national Agency for Meteorology, Hydrology. , Climate Change and its Impacts in Mongolia,2000) Improve water resources management and conservation. Reduce and control the number of livestock currently degrading the land. Improve pasture management, fodder quality and land management in general. Improve livestock quality, productivity, feeding and management. Introduce soil stabilization/enhancement techniques used in other dry climate areas & ownership/user-fee strategies to encourage long-term soil management. Land and Pasture Degradation Pasture degradation, land degradation and desertification are linked together, to climate change and to human activities. Man induced and natural land degradation is widespread throughout Mongolia, a major concern being that degradation is one step towards desertification. Land and
rangeland degradation are discussed in this section of the report; desertification in the next section. Natural rangeland occupies 1.26 million square km of Mongolia (80% of the country) where semi-nomadic pastoralism based on the animal husbandry of goats, sheep, cattle, horses, yaks and camels occupies approximately 25% of the country’s population. Some 78% of the country’s land is degraded and almost 21% threatened. Most degradation involves erosion by wind and water after the vegetation has been removed and the topsoil damaged by overgrazing, grasshoppers, Brandt’s voles, compaction by animals or vehicles, and removal by mining or deforestation. Another cause is land tillage in the spring when strong winds are common. There are no windbreaks and no care is taken to capture winter moisture in standing stubble or other mulch so that 35 to 50 tons of topsoil per cultivated ha has been lost to erosion over the past 30-years. ( source: Batjargal,, in Mongolia, Compendium of Discussion paper… at International Conference on Human Security, May,200, p.210)
Desertification Human activities are hastening desertification by deforestation, overgrazing and physical damage to the land itself that really contributes to dust storm. In the Mongolian context, the terms: “soil erosion”, “degradation”, and “desertification” refer to complex and inter-connected processes.( source: Mongolia, national Agency for Meteorology, Hydrology. , Climate Change and its Impacts in Mongolia,2000, p.177) Desertification, in terms of land-cover change from vegetated to non-vegetated, may be relatively minor in Mongolia. Sand covers 42,200 sq, km (about 3 percent of the country), the extent of coverage being very stable over the past 40 years, having increased by just 0.02 percent. (source: Mongolia, national Agency for Meteorology, Hydrology. , Climate Change and its Impacts in Mongolia,2000, p.186 and Peter Marriot, B. Erden-ochir, Ecological vulnerability and human security). On the other hand there seems to have been progressive drying up of lakes and streams in the south and damage by moving sand to wells and other structures. The Mongolian Agency for Meteorology, Hydrology and Environmental Monitoring estimates that recent desertification has affected a total of 800-1,500 ha in 10 different aimags located in the dry region of the country. (source: ADB, Mongolia: Country environmental analysis, 2002 ) Causes of desertification have been identified to include: Climate change. Low and uneven distribution of precipitation. Lower surface and ground water levels. Degraded pastureland. Mining. Over exploitation of forest and other plants. Forest and steppe fires. Insect and rodent infestations. 3. Mitigation measures to reduce DSS in Mongolia
The Government has a major role to play in providing support services, such as, disaster response programs, veterinary services, education and health care, credit programs, and assistance with transport to market. Continue development and implementation of environmental legislation, and pay special attention to possibilities to create economic incentives to reduce DSS Strengthen a national DSS monitoring system for the DSS. Also there is needed to develop DSS database and connect it to the Global Resources Information Network and data exchange. Promote public awareness program to reduce DSS Organize workshops, conferences and other meetings on DSS, impact assessment projects to encourage maximum public participation for DSS reduction in sources areas. Support and strengthen NGO involvement measures on reduction of DSS in sources areas. Conclude agreements with neighboring and other states on DSS reduction; develop international cooperation with international organizations to combat DSS. The DSS will be reduced if the above adaptation measures successfully implemented in Mongolia. There is need to take effective to share knowledge, plans and information about action programs with neighboring countries.