Climate characteristics, temperature changes, four seasons differentiation, precipitation and disasters in Ili, Xinjiang
Ili Kazakh Autonomous Prefecture is far away from the ocean and surrounded by mountains. It has typical arid climate characteristics and belongs to the semi-arid continental climate of the cold temperate zone. Due to the vast territory and complex terrain, from the Tianshan Mountains to the Altai Mountains, various places have unique microclimate characteristics depending on their longitude and location altitude. The general climate characteristics of the whole state are: short summer and long winter; rapid but unstable temperature rise in spring; rapid cooling in autumn. In general, spring is about 30 days longer than autumn. There is plenty of sunshine, low relative humidity and high evaporation. The temperature changes drastically and the diurnal temperature difference is large. The frost-free period is shorter. The monthly, seasonal and annual change rates of precipitation are large, more in mountainous areas than in plains, and there are large differences between local areas. Wind performance varies depending on the terrain. In terms of disastrous weather, cold air intrusion is common in late autumn and early spring, with temperatures dropping sharply and blizzards occurring. There are frosts in early winter, and disasters such as heavy rain, hail, and hot and dry winds in summer.
From a regional perspective, the temperature in the autonomous prefecture is 8-9°C in the Yili region, 7-8°C in the Tacheng region, and 0-4°C in the Altay region. , that is, the temperature gradually decreases as the terrain increases. January (February in mountainous areas) is the coldest and July is the hottest throughout the year. The average annual range is between 27-45℃. The difference is small in mountainous areas and large in plains. The average daily range in various places is 10-16℃. ℃, the maximum diurnal range is between 20-28 ℃.
In terms of light and heat, the annual average solar radiation flux in the autonomous prefecture is 5200-5600 megajoules/square meter. The Altay region has a high latitude and a photothermal resource of 5399 MJ/m2, making it a low-value area in the autonomous prefecture. The solar radiation flux in Yining City and Huocheng County is 5563 MJ/m2, which is a high-value area of photothermal resources in the autonomous prefecture. The photosynthetic potential that can be utilized by plants in the state is generally 2600-2800 megajoules/square meter. The annual sunshine hours in the autonomous prefecture range from 2899 to 3158 hours, and the average sunshine ratio is 65%.
The frost-free period in the plain agricultural areas of the autonomous prefecture is generally 150-180 days. The longest period in Yining and Shawan counties is 191 days. In mountainous areas, it takes 100-130 days.
The precipitation in the Autonomous Prefecture is affected by atmospheric circulation and topography. Under the combined action of the warm and humid Atlantic air flow brought by the westerly jet stream and the Arctic air flow going south, it encounters Xichang, north and southeast, surrounded by mountains on three sides. The closed area forms "three belts and four blocks" with different precipitation characteristics.
The general trend of evaporation in the autonomous prefecture is to increase from south to north, and the annual evaporation in the prefecture is 1259-2381 mm. The largest evaporation occurred in Heishantou in the Altay region, reaching 2,331 mm; the smallest evaporation occurred in Zhaosu County, with only 1,209.5 mm.
The air pressure within the autonomous prefecture is irregular due to the huge difference in altitude. In areas with an altitude above 1,000 meters, the air pressure is below 900 hPa; in areas with an altitude below 1,000 meters, the air pressure is above 900 hPa. Its inter-annual changes are irregular and the amplitude is not large. The diurnal variation is highest in the early morning, reaches the lowest in the afternoon, and then begins to rise again, basically inversely changing with the diurnal variation of temperature.
The wind speed in the autonomous prefecture is higher in the north than in the south. The changes in the year generally increase from March to November and decrease again. The opposite is true in some areas.
The main disaster weather conditions in the autonomous prefecture include the intrusion of cold air or cold wave in early spring and late autumn, the temperature drops sharply, and there are snowstorms. There are frosts in early winter, and disasters such as heavy rain, hail, and hot and dry winds in summer. Cold waves mostly occur in spring and autumn, and the invasion mainly comes from strong cold air from the north or west. The invasion usually starts at the end of September. Thunderstorms and hail mostly occur in mountainous areas and front mountain areas, generally from April to October, and mainly from May to August. Strong winds are mainly concentrated from April to October.