Geography
[edit]
At 1,600 metres (5,200 ft) above sea level, Lanzhou lies in China's northwest geographical center. The metropolitan area covers more than 20 square kilometres (7.7 sq mi) of urbanisation along the southern banks of the Yellow River, which flows through from west to east. The Qilian Ranges, Mt. Pingliang, and Mt. Kongtong are located on the south and north sides of the city.
Lanzhou is situated on the upper reaches of the Yellow River where it emerges from the mountains and has been a center since early times, being at the southern end of the route leading via the Hexi Corridor across Central Asia. It commands the approaches to the ancient capital area of Chang'an (modern Xi'an) in Shaanxi province from both the west and the northwest, as well as the area of Qinghai Lake via the upper waters of the Yellow River and its tributaries.
Panorama of Chengguan District (city centre), seen from the Lanshan mountain park.
Climate[edit]
Lanzhou is situated in the temperate zone and has a semi-arid climate (Köppen BSk) with hot summers and cold and very dry winters. In the urban core, based on 1971–2000 normals, the monthly 24-hour average temperature ranges from −4.1 °C (24.6 °F) in January to 23.4 °C (74.1 °F) in July. The mean annual temperature is 10.9 °C (51.6 °F), while annual rainfall is 309 millimetres (12.2 in), almost all of which falls from May to October. The winters are so dry that snowfall is sometimes restricted to fall and spring. With monthly percent possible sunshine ranging from 47 percent in September to 57 percent in April, sunshine is generous but not abundant, as the city receives 2,350 hours of bright sunshine annually.
Climate data for Lanzhou, elevation 1,517 m (4,977 ft), (1991–2020 normals, extremes 1951–present)
Month
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Year
Record high °C (°F)
17.1(62.8)
21.0(69.8)
29.0(84.2)
34.6(94.3)
35.5(95.9)
36.8(98.2)
39.8(103.6)
37.3(99.1)
34.4(93.9)
30.5(86.9)
20.3(68.5)
16.5(61.7)
39.8(103.6)
Mean daily maximum °C (°F)
2.3(36.1)
7.6(45.7)
14.1(57.4)
20.7(69.3)
24.9(76.8)
28.6(83.5)
30.2(86.4)
28.8(83.8)
23.6(74.5)
17.5(63.5)
10.3(50.5)
3.5(38.3)
17.7(63.8)
Daily mean °C (°F)
−4.1(24.6)
0.6(33.1)
7.0(44.6)
13.2(55.8)
17.7(63.9)
21.7(71.1)
23.4(74.1)
22.2(72.0)
17.2(63.0)
10.7(51.3)
3.5(38.3)
−2.9(26.8)
10.9(51.5)
Mean daily minimum °C (°F)
−8.4(16.9)
−4.3(24.3)
1.6(34.9)
7.2(45.0)
11.5(52.7)
15.8(60.4)
17.9(64.2)
16.9(62.4)
12.6(54.7)
6.1(43.0)
−0.9(30.4)
−7.0(19.4)
5.7(42.4)
Record low °C (°F)
−21.1(−6.0)
−17.6(0.3)
−11.6(11.1)
−5.7(21.7)
−0.1(31.8)
5.7(42.3)
9.8(49.6)
8.6(47.5)
1.6(34.9)
−7.1(19.2)
−12.3(9.9)
−19.7(−3.5)
−21.1(−6.0)
Average precipitation mm (inches)
1.7(0.07)
3.0(0.12)
6.7(0.26)
16.3(0.64)
39.0(1.54)
44.0(1.73)
63.5(2.50)
66.0(2.60)
43.7(1.72)
21.7(0.85)
2.7(0.11)
0.7(0.03)
309(12.17)
Average precipitation days (≥ 0.1 mm)
2.4
2.4
3.7
5.8
7.8
8.9
10.7
10.1
9.9
6.5
2.1
1.0
71.3
Average snowy days
4.9
4.4
3.3
0.9
0.1
0
0
0
0
1.0
3.1
2.9
20.6
Average relative humidity (%)
51
46
42
40
44
48
55
58
63
63
58
54
52
Mean monthly sunshine hours
149.7
173.1
210.3
226.0
245.1
234.0
239.6
226.6
173.2
173.6
155.5
143.1
2,349.8
Percentage possible sunshine
48
56
56
57
56
54
54
55
47
51
51
48
53
Source 1: China Meteorological Administration
Source 2: Weather China
Environmental problems[edit]
View on Zhongshan Bridge from Baita Mountain Park
Further information: Environment of China
The city is located in a narrow and curved river valley with surrounding mountains causing it to be hemmed in blocking a free flow of air. According to the National Environmental Analysis released by Tsinghua University and The Asian Development Bank in January 2013, Lanzhou was among the ten most air-polluted cities in the world. Air quality reportedly was so poor that at times one could not see Lanshan, the mountain rising up along the south side of the city. Lanzhou is also the home of many factories, including some involved in petroleum processing, and suffers from large dust storms kicked up from the Gobi Desert, especially in the winter and spring. In 2011, using Chinese statistics, the World Health Organization reported that Lanzhou had the worst air quality among eleven western Chinese cities. Its annual mean PM10 μg/m3 of 150 is 7 times the safe level established by the World Health Organization. It was worse than Beijing with its reading of 121.
Since then, authorities have taken measures to improve air quality, which have largely been successful. "Thirteen polluting enterprises with excessive capacity have been closed, more than 200 highly polluting enterprises were suspended in winter, and 78 industrial enterprises have moved to an industrial park outside the city." In 2015 it was awarded China's climate progress title. As a city once unable to be spotted from satellites, Lanzhou has taken various measures to combat air pollution in recent years, having reduced its Air Pollution Index at the fastest speed across China. According to the 2018 WHO database, of 2700 towns listed, Lanzhou has the 158th highest level of PM 2.5 pollution, with an average of 54 micrograms per cubic meter (twice that of Milan). The large particle PM10 remains high, at 132 micrograms per cubic meter, in part as a result of sand storms.
The reach of the Yellow River at Lanzhou carries a high load of silt, giving the river its characteristic muddy appearance; however water quality in this reach is better than the "fetid outflow that barely passes for water two hours downstream" (2008). In recent years, several specimens of the endangered Chinese giant salamander have been found in and near the Yellow River in Lanzhou.
On April 11, 2014, Lanzhou officials advised residents not to drink tap water, because benzene levels were 20 times the national limit of 10 micrograms per liter. The city water supply suspected industrial chemical production to be the culprit, similar to what happened in the 2005 Jilin chemical plant explosions.
A brucellosis outbreak infecting humans took place in Lanzhou in 2020 after the Lanzhou Biopharmaceutical Plant involved in vaccine production accidentally pumped out the bacteria into the atmosphere in exhaust air, due to use of expired desinfectant, and affecting over 3,000 people.
Earthquakes[edit]
Lanzhou experiences earthquakes regularly, although usually at low intensities. In 1920 a large earthquake was experienced killing more than 100,000 people in Ningxia and Eastern Gansu province, although only 42 were killed in Lanzhou itself, the low number being attributed to the strong yet flexible nature of the wooden buildings in the city. Lanzhou was also affected by 2008 Sichuan earthquake in 2008.