Climate in the Chui Valley
The Chui Valley is located in the extreme southern part of the temperate zone, farthest from the oceans and close to the deserts of Kazakhstan, which determines the high amount of heat, continentality, and dryness of its climate. In the central part of the Chui Valley (the capital Bishkek), the average annual sunshine duration is 2584 hours, which is more than in Almaty (by 6-13%) and less than in Cholpon-Ata (2613 hours) and Karakol (2657 hours).
The maximum duration of sunshine hours occurs in June-August (300-337 hours), while the minimum is in December-February (121-131 hours), which corresponds to 36% and 14% of the annual total sunshine hours, respectively. A large number of sunshine hours generally indicates a high amount of solar radiant energy. The maximum midday intensity in Bishkek is 1.53 cal/cm² min, observed in March when air transparency was high. In the other months of the spring-summer period, due to increased atmospheric dust, increased water vapor, and the appearance of haze, absorption and scattering of radiation increase, and the intensity of radiation decreases. The total solar radiation in the area of Bishkek is 92.8 kW/m², and it increases with altitude. In summer and autumn, direct radiation predominates in the Chui Valley, while in winter, diffuse radiation prevails; the share of absorbed radiation over the year is 70-80% of the total radiation.
On average, the radiation balance in Bishkek is 34.9 kW/m². Its maximum is noted in May-July. Tables 3 and 4 provide data on total solar radiation and the radiation balance of the active surface at the actinometric station in Bishkek over a long observation period.
The position of the Chui Valley in the northern part of the republic and its openness to the north and northwest facilitates the free penetration of cold air masses of Arctic origin. In winter, the valley is most often under the influence of the southwestern ridge of the Asian maximum and experiences cold frosty weather, which is occasionally interrupted by thaws. Due to the weakening of the influence of the Asian maximum in spring, Mediterranean cyclones gain access to the Chui Valley, bringing unstable weather with precipitation and returns of cold. In summer, a thermal depression establishes over the valley, as well as over all of Central Asia, under the influence of which cloudless, dry, hot, and hazy weather develops. Only over the mountain ridges do powerful convective movements develop, and cumulus cloudiness is observed.
In autumn, due to the decrease in insolation, the frontal zone shifts southward, and the thermal depression weakens and is replaced by frequent cold incursions from the west, northwest, and north, which are associated with slight cooling.
According to long-term average data, the highest pressure is noted in January around the Bishkek station, equal to 698 mb (928 mb). With altitude, pressure decreases significantly. Up to an absolute height of 1000 m, pressure drops by 11 mb for every 100 m, and above 3000 m - by 8 mb. In the annual course of pressure in the lower zone (up to 1000 m), the minimum is observed in July-August when a thermal depression is established throughout Central Asia, and the maximum is in October-December when the Asian maximum is actively influencing. Starting from January, the average monthly pressure decreases, and breakthroughs of southern cyclones intensify. The wind regime of the Chui Valley is formed by these two powerful centers of atmospheric action. Significant complications in the wind regime are also caused by the orographic structure of the territory. Due to the latitudinal extent, western and eastern winds prevail in the Chui Valley. Cold and moist air masses are associated with western winds. Their speed exceeds 5-8 m/s. They are most frequent in spring and autumn. Eastern winds are more common in summer and winter. Overall, the valley has weak winds, with an average annual speed ranging from 1 to 4.1 m/s. The average annual number of days with strong winds of 15 m/s is noted at the Bishkek station - 18, Belovodsk - 15, Chon-Aryk - 10.
Winds are not as frequent in the mountains (gorges). Usually, calm sunny weather prevails here, while in the foothill plains where Bishkek is located, winds are a rare phenomenon.
In the valley part, the average monthly wind speeds do not exceed 3 m/s, only at the Konstantinovskaya station do they reach 3.7 m/s; in the foothills and mountain valleys, they are even lower (Chon-Aryk - up to 2.3 m/s).
The number of days with strong winds in the Chui Valley can reach 18-20 per year.
According to long-term data, the average annual wind speed in Bishkek is 1.9 m/s within the city, while on its southern outskirts it is 2.6 m/s. For urban planning, the distribution of wind by altitude is of great importance. According to data from the aerological station, in the 1000-meter layer above Bishkek, western and northwestern winds prevail for most of the year (up to 40-50%), while eastern and southeastern winds account for up to 30-40%. The maximum wind speed in the 1000-meter layer can reach 30 m/s /Climate. Frunze, 1990, p.53/.
Along with this, local winds arise in the mountains of the Kyrgyz Ala-Too, which blow down from the mountains at night (mountain winds), especially along the gorges - valleys, and during the day, conversely, blow up into the mountains, forming valley winds. Sometimes they reach great strength, which all travelers in the mountains have had to observe repeatedly. Usually, the speeds of such winds range from 1.8 to 2.3 m/s.
The great variety of relief from foothill plains to high mountains and significant altitude fluctuations (from 500 to 4895 m) determine the pronounced altitudinal zonality and the sequential change of seasons in the region under consideration.
The continentality of the climate is reflected in the annual, monthly, and daily temperature trends. Thus, the average annual air temperature in the northern part of the valley is -8.5°C /Chui/, in the central part of the plain it is 10.1°C /Bishkek/. In the foothills, it is 6.3° - 7.3°C /Baitik, Arashan/, and in the high mountains, it is 1.0° - 1.4°C /Ala-Archa, Tyo-Ashuu/. The average temperature in January in the agricultural zone /Chui, Bishkek, Kant/ is -9.5° - -5.0°, -6.0°C; in the high mountains /Ala-Archa, Tyo-Ashuu/ - -12°C; the average temperature in July is 27.7°, 24.4° and 8.6°, 8.5°C /Tyo-Ashuu, Ala-Archa/.
