Geography
Yan'an is located in the north of Shaanxi Province, in the middle reaches of the Yellow River, between latitude 35°21′~37°31′ north, longitude 107°41′~110°31′ east, in the south-central region of the Loess Plateau, 371 kilometersnorth of Xi'an. The city is connected to Yulin in the north, and Xianyang, Tongchuan and Weinan in the south, faces Linfen and Lvliang in Shanxi across the Yellow River in the east,and is next to Qingyang in Gansu in the west. The city has a total area of 37,000 square kilometers, withan inland arid and semi-arid climate, four distinct seasons, abundant sunshine, large temperature difference between day and night, an average annual frost-free period of 180 days, an average annual temperature of 10.1℃, an average annual sunshine of 2,271.1 hours, and an average annual precipitation of 570.6mm.
Topography and Geomorphology
Yan'an is located in the middle reaches of the Yellow River and belongs to the Loess Plateau Hills and Gullies area, with the topography dominated by the Loess Plateau and hills, the terrain high in the northwest and low in the southeast, and an average elevation of about 1,200 meters. Baiyu Mountain in the north is 1,600-1,800 metersabove sea level, with the highest point at the top of Baiyu Mountain in Wugucheng Township, Wuqi County, at 1,809.8 metersabove sea level; and the lowest point is in Monkey River in Jiyi Township, Yichuan County, at 388.8 metersabove sea level, with a relative altitude difference of 1,421 meters. The northern part is mainlyloess ridges and hills,and gullies, accounting for 72% of the total area of the region; the southern part is mainlyloess plateau gullies, accounting for 19% of the total area; the stony mountains of the region account for 9% of the total area. The western ZiwuRidge, orientated north-south, constitutes the watershed of Luohe River and JingheRiver, and is one of the bedrock mountains above the Huangshi Plateau, with an elevation of 1500-1600 metersand a main peak of 1687 meters; the eastern Huanglong Mountain, extending roughly north-south, with an elevation of 1,500 meters, and a main peak (DalingRidge) of 1,788.7 meters; and the central Laoshan Mountain, orientated north-northwest - south-east, with an average elevation of 1,400 meters, and a main peak (Dadunliang) of 1,464 meters. Huanglong Mountain and Laoshan Mountain are collectively known as Liangshan Mountain Range, forming the framework of the topography of Yan'an area.
Climate
Basic climatological data ofYan'an (according to the data of 1991-2020) | ||||||||||||
JAN. | FEB. | MAR. | APR. | MAY | JUN. | JUL. | AUG. | SEP. | OCT. | NOV. | DEC. | |
Aver. temp (℃) | -5.4 | -1.1 | 5.3 | 12.2 | 17.1 | 21.3 | 23.2 | 21.5 | 16.3 | 9.8 | 2.8 | -3.7 |
Aver. max. temp (℃) | 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 max. temp (℃) | 10.4 | 16.2 | 23.8 | 29.9 | 32.3 | 34.7 | 35.3 | 33.4 | 30.1 | 24.5 | 19.4 | 11.4 |
Aver. min. temp (℃) | -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 min. temp (℃) | -20.0 | -11.8 | -8.8 | -2.4 | 2.0 | 7.9 | 11.3 | 11.2 | 3.7 | 0 | -11.7 | -19.6 |
Aver. precipitation (℃) | 4.4 | 6.8 | 13.6 | 27.7 | 43.9 | 63.8 | 119.0 | 112.0 | 75.8 | 39.5 | 15.5 | 2.8 |
Number of days with precipitation (day) | 3.5 | 3.4 | 4.2 | 5.6 | 7.2 | 8.6 | 11.2 | 10.9 | 9.7 | 7.5 | 4.6 | 2.7 |
Aver. 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 is of theplateau continental monsoon climate, the northern part isthe semi-arid region, andsouthern part the semi-humid region. The winteris cold,dry, andlong; the spring temperature rise fast and changerapidly, prone to frost, windy, sandy, dusty weather, often with an early spring: the summeralways has high temperature,with concentratedrainfall, orsummerdroughtsomewhat, more thunderstorms, and occasional hail; the autumn temperature fallsfast, foggy, with early frost, and cloudy and rainy weather. The dailytemperaturedifference is large, that the region's annual average daily difference is11.1 ~ 14.9 ℃, with the largestin FuxianCountyand the smallest in LuochuanCounty. For a wholeyear, the daily temperature difference is largerfrom April to June, with an average of 15 ~ 16 ℃, but relativelysmallerfrom July to September, with an average of 11 ~ 12 ℃.
I. Temperature: The average annual temperature is 9.9℃, the average annual maximum temperature is 17.7℃, the average annual minimum temperature is 4.1℃, the average monthly temperature of the hottest month (July) is 23.2℃, the average monthly temperature of the coldest month (January) is -5.4℃, the extreme maximum temperature is 41.5℃ (June 22, 2005), and the extreme minimum temperature is -28.7℃ (December 26, 2002).
II. Precipitation: The average annual precipitation is 524.8 mm, the maximum precipitation in one day is 195.3 mm (July 4, 2002), the number of days with precipitation≥0.1 mm per year is 79.1, the number of days with precipitation≥50 mm per year is 7.8, the maximum annual precipitation is 772.8 mm (2013), and the maximum annual precipitation is only 346.1 mm (1997), and the precipitation is mainly concentrated in May-September, with the maximum average monthly precipitation in July, at 119.0 mm.
III. Sunshine: The annual sunshine hours are 2,408.9 hours, with a maximum of 246.0 hours in May and a minimum of 167.1 hours in September. The annual sunshine percentage is 55%, the maximum is 62% in December, and the minimum is 46% in September.
IV. Wind: The annual average wind speed is 1.5 m/s, with the maximum wind speed of 17.9 m/s, north-northwest (NNW), appeared on July 12, 2017; the annual maximum wind directions are north-northwest and calm wind (NNW, C).
V. Days of weather phenomena: 3.2 days of high winds; 0.3 days of sandstorms, mainly in April; 19.9 days of fog, with a maximum of 8.7 days in September; 23.2 days of hail, mainly in June; 26.4 days of thunderstorms, with a maximum of 8.0 days in July; and 185 days of frost.
VI. Sunrise and sunset time: On the spring equinox, sunrise at 06:47 and sunset at 18:53; on the summer solstice, sunrise at 05:24 and sunset at 20:04; on the autumn equinox, sunrise at 06:30 and sunset at 18:38; on the winter solstice, sunrise at 07:50 and sunset at 17:30.