A Spreading Surface

Most part of the Altai territory exhibits slightly hilly plains of the West- Siberian lowland rising gradually in steppes to the heights of the Salair mountain ridge in the east and the Altai mountain area in the southeast. The Altai mountains, along with the mountain ridges of Kazakhstan, provide an orographic border be­tween the plateaus of Central Asia and the plains of Western Siberia. They direct the prevailing movement of air masses: southwest winds.

In anticyclonic summer weather usually cools when the steppe plains are foil of hot continental air. The ascending movements of air along windward mountain- ridge slopes causes the formation of clouds and subsequent precipitation. In the cold season the slopes of moimtain-ridges get warmer due to foehns and inversion of temperatures, when cold dense air flows down and stands in intermountain hol­lows,. The total area occupied with ridges and spurs is more than the area of moun­tain valleys, therefore Altai on the whole gets warmer than surrounding plains filled with cold air. The arrival of warm air from some valleys is spurred by the "buffer" layer of warm air formed in a transitive zone «of the Altai foothills ».

Therefore in the front of the Altai plain and in the foothills of Altai the frostless period is prolonged, and winters are less severe. From Zmeinogorsk and

Kolyvan up to Belokurikha and Turochak the best climate in the Altai territory is observed, with mild snow in winter and warm rather damp summers.

The heating of Teletskoe Lake in spring is slower than the heating of the land, while in autumn the cooling is slowed down. Therefore temperatures shown by Yailyu meteorological stations on the northeastern coast in May and June are reduced by 2,5°C, and in winter temperatures increase by 1-3°C in comparison with the temperatures of the middle latitudes.

The specific interplay of climate forming factors within the Altai mountain area has resulted in the appearance of the freezing centers (poles).

Thermal Mode of Air and Ground

A very intensive increase from March to April and sharp decrease (reduction) from October to November are characteristic of an annual course of air tempera­ture. March is stil! a typical month, depending on the extent of snow cover and low temperatures (despite of the beginning of thawing) as well as in all Western Siberia. The stable transition of average air daily temperature through 0°C in the southwest part of the Altai territory and at the coast of Teletskoe Lake occurs in the first week of April, while in intermountain hollows of South-East Altai - only at the end of April. The change of daily temperature through IOC⁰ is the beginning of summer and is observed between the 8^th and 20^th of May, while in mountain val­leys and hollows it occurs on the 11th of April.

In spring and early summer, frosts are quite possible. For example, this oc- cured on the 7^th of June, 3973, in Barnaul. The average date of autumn frosts is the third week of September, but it is also possible as early as August 29, as seen in Barnaul in 1941.

The hottest summer in the region is observed in Kulunda and in the south­east, where average monthly temperatures during July are roughly 21C°. The sums of active temperatures (are higher than 10C°) range from 2400° in the specified ar­eas to 1600^c in the forest low mountains of Salair and in the forest middle moun-

tains of Altai. In the process of rising upwards in mountains the sum of tempera­tures decrease by 80-100C⁰ every 100m, on average, reaching 1000C° in Kosh- Agach (1750 m). The difference of average monthly air temperatures for all sta­tions of Altai in the summer is insignificant (up to 4°) in comparison with winter (up to 20°). The warmest summer in the region is observed in areas of Chemal, Kyzyl-Ozek and Turochak, with temperatures in July of about 18° and only 6° on high-mountainous water sheds.

In some years increases of temperature of up to 41C° in Kulunda and Aleysk, 36° in Turochak and 31° in Kosh-Agach are possible (absolute maximum). But a significant lowering of temperature (absolute minimum) to 0°C in Turochak and -4° in Kosh-Agach may also occur.

The return shift of average daily temperature of air through 0° takes place during the third week of October. In winter the lowest air temperatures on the plain are found in the north of region and in Kulunda, from -19.2°C to -19.9°C. In the foothills of Zmeinogorsk it is -15.5°C, and in Belokuricha -16.8°C.

In the mountains the distribution of winter air temperatures depends on the topography and the height of the district. In Ak-Kem, 2058 m, temperatures in January are -21. 1°C. In Chuisk hollow, where "the lakes of chill" are formed, in Kosh-Agach, 1760 m, it is -32.2°C in Jan uary. On the coast of Teletskoe Lake, in Beiya and Yailyu, January temperatures are -9.2 to -9.4°C.

January is typically the coldest month, though in some years it can be .Feb­ruary. The 40°C frosts are possible even in the southern areas and the absolute minimums are -52° in Barnaul, -53° in Biysk, -55° in Turochak, -58° in Ust- Ulagan and -62° in Kosh-Agach. March is colder than November.

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he freezing depth of soil under natural cover reaches 150-200 cm for black earth and loamy soils of forest-steppe and forest zones. In the valleys of the Northern Altai region the freezing depth of the ground is 20-50 cm and in the hol­lows of Central Altai it is 1.5-2.5 mm.

Mode of Humidifying

The annual amount of precipitation in the flat territory of Altai changes from 240-250 mm in Kulunda and in the extreme southwest up to 500-550 mm in the southern part of the Biysk-Chumyshsk heights. Such distribution of precipita­tion in general causes the climate transition of the droughty steppe to the forest- steppe. Besides, because of significant heterogeneity of a spreading surface, there are also local peculiarities in humidity. So, the increased quantity of atmospheric precipitation is observed in areas of winding forests. The annual quantity of pre­cipitation in the Altai foothills grows from west to east from 550-650 mm up to 880-850 mm.

The most irregular precipitation occurs in the mountain territory of the re­gion. The most humid areas are the windward mountain slopes of southwest Altai, towering above the neighboring areas which are the first to take the moisture of western flows (up to 2000 mm). A maximum quantity of precipitation in the mountain glacier, pools (more than 2500 mm) falls in the Cholzunsk mountain- ridge. The same features cause the significant quantity of precipitation that fells in the western part of the Katunsk mountain-ridge (up to 2000 mm).

The lowest amount of precipitation is received in the inter-mountain hollows of the southeast - Chuisk hollow (127 mm for one year), Kuraisk hollow (250 mm) and Ukok plateau (230 mm).

During the annual cycle, the maximum quantity of precipitation is observed in July and the minimum in February and March. The distribution of precipitation across the seasons is not regular. During the warmer half-year (April - October), as a rule, about 70% of the annual quantity of precipitation occurs, while only 30% falls in spring and in the first half of summer. April is the driest month. The second half of summer is richer in precipitation. The humidity is greater in the majority of areas of Altai region during autumn rather than in spring, aggravating crop harvest­ing. Only in the central and eastern areas of the mountain territory autumn is drier than spring.

Taking into consideration the most favorable thermal conditions, the cultiva­tion of basic grain agriculture is best on the left bank of the Ob. The basic factor reducing the efficiency of crops in the territory of the Altai region is the lack of moisture. This climate feature is also aggravated by sharp changes of humidity every year.

During the cold period approximately 30 % of the annual precipitation oc­curs. Very little precipitation is observed in the steppe, where auticycionic weather dominates. Therefore, the depth of a snow cover there is low (10-15 cm) and the spring stocks of moisture are insufficient Only in areas close to the Ob does the quantity of winter precipitation increase to 150 mm. The snow cover in the moun­tains of Altai is 1-3 m, in the intermountain hollows it is only 10-20 cm.