Geographical Conditions
Yan’an is located in the northern part of Shaanxi Province.Situated in the middle reaches of the Yellow River, it lies between 35°21’N and 37°31’N and 107°41’E and 110°31’E, and is in the central-southern area of the Loess Plateau. It is 371 kilometers north of Xi’an, andis adjacent to Yulin in the north, connects with suchcities asXianyang, Tongchuan and Weinan in the south, is separated from Shanxi’s Linfen and Luliang by the Yellow River to the east, and is nextto Gansu’s Qingyang to the west. The total area is 37,000 square kilometers. It has an inland arid and semi-arid climate, with distinct four seasons, abundant sunshine, large day-night temperature difference, an average frost-free period of 180 days, an average annual temperature of 11.0℃, an average annual sunshine duration of 2,104.7 hours, and an average annual precipitation of 517.2 millimeters.
Geographic Conditions
Located in the middle reaches of the Yellow River, Yan’an is the hilly and gully area of the Loess Plateau. The landformis mainly composed of the Loess Plateau and hills. The terrain is higher in the northwest and lower in the southeast, with an average altitude of about 1,200 meters. The Baiyu Mountain in the north has an altitude of 1,600-1,800 meters, mounting to the summit atthe Baiyu Peak in WuguchengTownship, Wuqi County, at an altitude of 1,809.8 meters; the lowest partis at the Hou’erchuanin Jiyi Township, Yichuan County, at an altitude of 388.8 meters, boastinga relative height difference of 1,421 meters. The northern part is mainly composed of Loess hillsand gullies, accounting for 72% of the total area; the southern part is mainly composed of Loess gullies, accounting for 19% of the total area; the stone mountainous areas in the region account for 9% of the total. The Ziwu Mountain Ranges in the west is in anorth-south direction, forming the watershed between the LuoheRiver and the JingheRiver. Itis one of the rock mountainous areas higher than the Loess Plateau, with an altitude of 1,500-1,600 meters, and the main peak mounts to1,687 meters; the Huanglong Mountain in the east extends roughly in a north-south direction, with an altitude of 1,500 meters, and the main peak (Daling) is at 1,788.7 meters; theLaoshanMountainin the central areais in a northwest-southeast direction, with an average altitude of 1,400 meters, and the main peak (Dadunliang) is at 1,464 meters. The Huanglong Mountain and Laoshan Mountain are collectively called the Liangshan Mountains, forming the framework of the terrain in the Yan’an area.
Climate
Basic Climatological Data of Yan’an (Based on Statistics from 1991-2020) | ||||||||||||
Jan. | Feb. | Mar. | Apr. | May | Jun. | Jul. | Aug. | Sep. | Oct. | Nov. | Dec. | |
Avg. Temp (°C) | -5.4 | -1.1 | 5.3 | 12.2 | 17.1 | 21.3 | 23.2 | 21.5 | 16.3 | 9.8 | 2.8 | -3.7 |
Avg. High (°C) | 2.8 | 7.1 | 13.5 | 20.6 | 25.2 | 29.0 | 29.9 | 28.0 | 23.2 | 17.6 | 10.8 | 4.3 |
Extreme High (°C) | 10.4 | 16.2 | 23.8 | 29.9 | 32.3 | 34.7 | 35.3 | 33.4 | 30.1 | 24.5 | 19.4 | 11.4 |
Avg. Low (°C) | -11.2 | -7.0 | -1.2 | 4.9 | 9.8 | 14.5 | 17.8 | 16.8 | 11.6 | 4.6 | -2.5 | -9.2 |
Extreme Low (°C) | -20.0 | -11.8 | -8.8 | -2.4 | 2.0 | 7.9 | 11.3 | 11.2 | 3.7 | 0 | -11.7 | -19.6 |
Avg. Precipitation (mm) | 4.4 | 6.8 | 13.6 | 27.7 | 43.9 | 63.8 | 119.0 | 112.0 | 75.8 | 39.5 | 15.5 | 2.8 |
Rainy Days | 3.5 | 3.4 | 4.2 | 5.6 | 7.2 | 8.6 | 11.2 | 10.9 | 9.7 | 7.5 | 4.6 | 2.7 |
Avg. Wind Speed (m/s) | 1.4 | 1.5 | 1.8 | 1.9 | 1.8 | 1.6 | 1.5 | 1.4 | 1.4 | 1.4 | 1.4 | 1.5 |
Yan’an has a plateau continental monsoon climate. The northern part is a semi-arid region, while the southern part is a semi-humid region. The winter is cold and dry with a long duration; the spring has a rapid temperature rise and is variable, prone to frost, with frequent strong winds, sandstorms and dust storms, and early springoften occurs; the summer is warm and hot with concentrated rainfall, occasional droughts, andfrequent thunderstorms and occasional hail; the autumn sees a rapid drop in temperature, with fog and early frost, and rainy days. The daily temperature range is large, with the annual average daily range being 11.1 to 14.9℃. Fuxian has the largest daily range, while Luochuan has the smallest. During the year, the daily range is larger from April to June, averaging 15 to 16℃, and smaller from July to September, averaging 11 to 12℃.
I.Temperature: The annual average temperature is 9.9℃, the annual average maximum temperature is 17.7℃, and the annual average minimum temperature is 4.1℃. The average temperature in the hottest month (July) is 23.2℃, and the average temperature in the coldest month (January) is -5.4℃. The extreme maximum temperature is 41.5℃ (on June 22, 2005), and the extreme minimum temperature is -28.7℃ (on December 26, 2002).
Ⅱ.Temperature: The annual average temperature is 9.9℃, the annual average maximum temperature is 17.7℃, and the annual average minimum temperature is 4.1℃. The average temperature in the hottest month (July) is 23.2℃, and the average temperature in the coldest month (January) is -5.4℃. The extreme maximum temperature is 41.5℃ (on June 22, 2005), and the extreme minimum temperature is -28.7℃ (on December 26, 2002).
Ⅲ.Daylight: The annual sunshine duration is 2,408.9 hours. The maximum is 246.0 hours in May and the minimum is 167.1 hours in September. The annual sunshine percentage is 55%, with the highest at 62% in December and the lowest at 46% in September.
Ⅳ.Wind: The annual average wind speed is 1.5 m/s, the maximum wind speed is 17.9 m/s, the wind direction is north-northwest wind (NNW), and it occurred on July 12, 2017; the most frequent wind direction in a year is north-northwest and calm (NNW, C).
Ⅴ.Number of weather phenomena: Strong winds last for 3.2 days; sandstorms 0.3 day, mainly in April; fog 19.9 days, with the most being 8.7 days in September; hail 23.2 days, mainly in June; thunderstorms 26.4 days, with the most being 8.0 days in July; the frost period 185 days.
Ⅵ.Sunrise and sunset: On the Vernal Equinox, sunrise is at 06:47 and sunset at 18:53; on the Summer Solstice, sunrise is at 05:24 and sunset at 20:04; on the Autumnal Equinox, sunrise is at 06:30 and sunset at 18:38; on the Winter Solstice, sunrise is at 07:50 and sunset at 17:30.