Wei Li, Shanshan Zhao , Yu Chen, Qiuling Wang, Wanxiu Ai

National Climate Center, China Meteorological Administration, Beijing, China

Keywords:Climate state Meteorological disaster Rainstorm High temperature

A B S T R A C T This report is a summary of China’s climate, as well as major weather and climate events, during 2020. In 2020, the mean air temperature in China was 10.25°C, which was 0.7°C above normal (1981—2010 average), and the annual rainfall was 694.8 mm, which was 10.3% above normal. In general, disasters caused by rainstorms and flooding were more serious than those by drought. In summer, southern China experienced the most severe flooding with extreme heavy rainstorms since 1998. Drought brought slight impacts and losses in China. The seasonal transition from spring to summer was earlier than normal. High temperatures occurred earlier than normal with extreme values, and lasted longer than normal in summer over the south of China. The number of landfalling typhoons was lower than normal. Cold-air processes had a wide influence and brought a substantial decrease in air temperature in local areas. Compared with the average values of the past 10 years, the affected crop area and the numbers of deaths and missing persons in 2020 were significantly smaller, while direct economic losses were slightly larger.

1. Mean air temperature

According to a consolidation of five leading international datasets,the World Meteorological Organization announced in January 2021 that the global average air temperature in 2020 was about 14.9°C, which was 1.2 ( ± 0.1)°C above the pre-industrial (1850—1900) level, and one of the three warmest on record. Meanwhile, the mean air temperature over China in 2020 was 10.25°C ( Fig. 1 (a)), which was 0.7°C above normal(1981—2010 average). The annual mean air temperature was higher than normal in most parts of China, except parts of southeastern Chongqing.The annual mean air temperature in northern Northeast China, eastern and southern Jiangnan, eastern South China, northeastern Inner Mongolia, most of Hainan, central Yunnan, and northeastern Xinjiang was 1°C—2°C higher than normal ( Fig. 1 (b)).

The seasonal mean air temperature was above normal in China in every season. Specifically, the seasonal mean air temperature in winter (December 2019 to February 2020), spring (March to May), summer (June to August), and autumn (September to November) was 1.2°C,1.1°C, 0.5°C, and 0.5°C higher than normal, respectively. The monthly mean air temperature in December was 0.7°C below normal, while in all other months it was higher than normal.

Extreme high-temperature events occurred frequently over China in 2020. There were about 256 national meteorological stations where the daily maximum air temperature reached the level of an extreme high-temperature event in 2020, and 69 national meteorological stations where the observed daily maximum temperature exceeded the historical maximum record. Meanwhile, the frequency of extreme cold events in China was lower than normal. There were only 55 national stations where the daily minimum temperature reached the extreme event standard. Gangzi in Inner Mongolia ( - 32.4°C) and Xiaodian in Shanxi ( - 20.6°C) recorded their lowest daily minimum temperatures since 1961.

2. Annual precipitation

In 2020, the average annual rainfall in China was 694.8 mm and 10.3% more than normal, which ranked the fourth highest since 1951( Fig. 2 (a)). The year 2020 was the ninth consecutive wet year since 2012. The annual precipitation was more than normal in most of centraleastern China, while it was less than normal in the central-western part of Northwest China. The areas with annual precipitation 20%—100%above normal occurred in most of Jianghuai, most of Jianghan, southern and eastern Huanghuai, mid-northern Northeast China, northern Jiangnan, northeastern Inner Mongolia, southern Hebei, central Shanxi,central Sichuan, eastern Guizhou, and northern Guangxi. Meanwhile,the precipitation over central and southern Xinjiang, western Gansu,western Inner Mongolia, mid-northern Qinghai, and western Tibet was 20%—50% below normal ( Fig. 2 (b)).

Fig. 1. (a) Annual mean air temperature in China during 1951—2020 (units: °C), and (b) anomalies in 2020 (units: °C, relative to the 1981—2020 average).

Fig. 2. (a) Annual rainfall in China during 1951—2020 (units: mm), and (b) anomalies for 2020 (units: %, relative to the 1981—2020 average).

Fig. 3. China’s major weather and climate events during 2020.

Annual precipitation was higher than normal in 25 provinces (including autonomous regions and municipalities). Heilongjiang, Hubei,Anhui, and Guizhou experienced their wettest years since 1961. Precipitation over Tibet was close to normal. Meanwhile, annual rainfall in the other five provinces was less than normal, and that in Xinjiang was 21% less than normal.

Precipitation in winter, summer, and autumn was all above normal in China. The rainfall in winter was 55.5 mm and 35% more than normal in China as a whole and 125% and 82% more than normal in North and Northeast China, respectively. The rainfall in spring was 5% less than normal. In summer, it was 373 mm and 15% more than normal,ranking it the second wettest summer since 1961. The rainfall in autumn was 13% more than normal in China as a whole and 119% more than normal in Northeast China.

In 2020, the annual mean number of rainy days (daily precipitation greater than or equal to 0.1 mm) over China was 103.1, which was close to normal. In terms of heavy rain, the number of days with daily rainfall equal to or greater than 50 mm recorded by national stations was 7408 and 24.1% more than normal, which ranked second most since 1961. The number of heavy rain days in most parts of China was close to normal, while 3—5 d more than normal in the local areas of southern Anhui, northern Zhejiang, eastern Hubei, northwestern Hunan, and northeastern Guangxi.

The rainy season is an important factor affecting the characteristics of climatic evolution on the interannual scale in China. The main characteristics of the rainy season are shown in Table 1 . The onset and end of the first rainy season in South China in 2020 were earlier, with less rainfall than normal. The rainy season in Southwest China started later and ended earlier than normal, with abundant precipitation. The meiyu season started earlier and ended later. Both the duration and rainfall amount of mei-yu exceeded the historical record since 1961. The rainy season in North China and Northeast China, as well as the autumn rainy season in West China, all started and ended later than normal, with rainfall more than normal.

Table 1 Characteristics of the rainy season in 2020.

The number of extreme precipitation events in China in 2020 was more than normal. There were 354 national stations where daily precipitation reached the extreme event standard, among which 45 stationsexceeded their historical maximum record. Meanwhile, the maximum daily continuous precipitation of 54 stations exceeded their historical maximum value, and 58 stations recorded their longest duration of continuous precipitation days.

3. Major meteorological disasters in 2020

According to the preliminary statistics of relevant departments, meteorological disasters caused 552 deaths or disappearances, affecting 19.96 million hectares of agriculture areas and causing direct economic losses of 368.1 billion yuan in China in 2020. Compared with the average value over the past 10 years, the affected agriculture areas and numbers of deaths or disappearances in 2020 were all smaller, while the direct economic losses were larger ( Fig. 3 ). The agricultural areas affected by rainstorms and floods accounted for about 36% of all areas affected by all meteorological disasters. Meanwhile, droughts, typhoons, hailstorms, and low-temperature freezing and snow disasters accounted for 26%, 19%, 14%, and 5% of the total affected area, respectively. Generally, the losses caused by droughts, typhoons, severe convective weather, low-temperature freezing, snow disasters, and dust storms were all relatively limited in 2020. However, the losses caused by rainstorms and floods were relatively serious.

3.1. Rainstorms

In 2020, 37 regional heavy rain events occurred across China. In summer, southern China experienced its most severe flood since 1998.The losses caused by rainstorms and flood disasters were relatively heavier than normal.

The first rainy season in South China started on 25 March, which was 12 days earlier than normal. Although the total rainfall of the first rainy season in South China was less than normal, the rainfall from mid-May to the end of June was high. During 20—22 May there was a heavy rainfall process in Guangdong and Guangxi provinces, characterized by strong intensity and a wide range. The maximum daily precipitation in Guangzhou was 219.3 mm, which broke the local historical record for spring. The maximum 3-h rainfall in Dongcheng, Dongguan City, was 351 mm, also breaking the local historical record.

In summer, the total rainfall in China was the second largest since 1961. The summer total rainfall in the Yangtze River and Yellow River regions were their largest since 1961, and those in the Huaihe River and Taihu Lake regions were their second largest. Affected by rainstorms and floods, the losses in Anhui, Jiangxi, Hunan, Hubei, Sichuan, and Gansu were large.

From June to July, the main rain belt was located in Guizhou,Sichuan, Chongqing, and the middle and lower reaches of the Yangtze River. The rainfall in Anhui, Hubei, and Chongqing was 113%, 101%,and 67% more than normal, respectively, all of which were ranked the highest since 1961. The rainfall in Jiangsu, Zhejiang, Shanghai, and Henan was 78%, 39%, 74%, and 40% more than normal, respectively,ranking the second highest since 1961. Heavy rain caused basin flooding in the Yangtze River, Huaihe River, and Taihu Lake regions.

In August, the total rainfall and the number of heavy rain days in Sichuan ranked the first since 1961. During 17—18 August, Leshan City in Sichuan Province was attacked by rainstorms and flooding. The total rainfall in Northeast China, North China, eastern Northwest China,and Yunnan was more than normal. The total rainfall in Ganshu in August ranked the highest since 1961, and that in Shanxi, Shandong, and Heilongjiang ranked the second highest.

In autumn, 11 regional heavy rain events occurred in China. Two rainstorm events had a wide influence, which occurred during 7—8 September and 15—18 September, respectively. The affected regions were located in Northeast China, South China, eastern Southwest China,northern Jiangnan, and North China, where the rainfall was 50% more than normal. Eighteen provinces (including autonomous regions) were affected by rainstorms and flood disasters, and the losses in Guizhou,Hunan, Inner Mongolia, and Liaoning were especially serious.

3.2. Typhoons

In 2020, there were 23 typhoons (maximum wind force level ≥ 8 near the center) generated in the Northwest Pacific and the South China Sea, which was fewer than normal. There were five typhoons that made landfall in China, which was also fewer than normal. Compared with the direct economic losses caused by typhoons in the past 10 years, the losses were limited in 2020.

Typhoon activities in 2020 varied in different periods. Specifically,there were only two typhoons generated in the Northwest Pacific and the South China Sea from January to June, and no typhoons at all generated in July, which was the first time this happened since 1949. However,there were 21 typhoons generated from August to December. From late August to early September, Bavi, Maysak, and Haisen successively affected Northeast China, which was also the first time since 1949. The heavy rainfall induced by typhoons caused water levels of 48 rivers to exceed their warning levels, including the main stream of Songhua River.

The average landfall intensity was 30.8 m s1 (level 11), which was close to normal (30.7 m s, level 11). The intensity of landfalling typhoons increased in the offshore areas, and those that made landfall in China had maximum intensity.

3.3. High-temperature days

In summer, the average number of high-temperature days (daily maximum temperature ≥ 35°C) in China as a whole was 8.0, which was 1.1 more than normal. The number of high-temperature days was about 3—10 more than normal in Zhejiang, central and southern Jiangxi,southeastern Hunan, Fujian, Guangdong, southern Guangxi, Hainan,and northeastern Yunnan; and over 10 d more than normal in southern Jiangnan and eastern and southern South China. The area-averaged number of high-temperature days was 36.5, 29.4, and 27.5 in Fujian,Hainan, and Guangdong, respectively, which ranked the highest since 1961. High-temperature events in southern China were characterized by extremely strong intensity and long duration.

During 1—9 May the first high-temperature process of 2020 occurred in central and eastern China, which was 49 d earlier than normal.The extreme maximum air temperature value was about 35°C—38°C in western North China, western Huanghuai, western Jianghuai, Jiangnan, South China, eastern Southwest China, northeastern Shannxi, and southeastern Inner Mongolia. The extreme maximum air temperature of Yuanyang in Yunnan Province reached 42.7°C. There were about 30 stations that broke their maximum high-temperature historical records.

During 2—8 June the extreme maximum air temperature value was 35°C—38°C in southern North China, most of Huanghuai and Jianghuai,in eastern and southern Shannxi, and in eastern Sichuan; and that in western Shandong, southwestern Hebei, and northeastern Henan exceeded 38°C. The daily maximum temperature at 21 stations, such as Jiaozuo (41.9°C) in Henan, Cixian (41.8°C) in Hebei, and Liangshan (40.8°C) in Shandong, reached the standard for extreme hightemperature events.

From 11 July to 3 September, southeastern Jiangnan and eastern South China experienced continuously high temperatures. The duration of this process ranked the second longest since 1961. The extreme maximum temperature exceeded 35°C in Jiangnan, South China, eastern Sichuan, northern Guizhou, and Chongqing. The maximum temperature of 41.1°C occurred at Minhou in Fujian Province. A total of 24 stations,including Nanjing (40.7°C) and Pinghe (40.5°C) in Fujian, broke their maximum high temperature historical records.

3.4. Drought

Drought occurred frequently in local areas in China, and the influence of drought was limited.

In mid-April, drought occurred in the northern part of the Yangtze River area, and severe drought occurred in southern Ningxia. Rainfall processes during 4—9 May alleviated the drought in most of northwestern China and western Huanghuai. From mid-May to early June,drought in western Huanghuai, Jianghuai, and Jianghan developed quickly.

Southwestern China experienced drought in spring and summer. On 11 April, the areas affected by drought in Yunnan amounted to 195 000 km. North China and South China were attacked by drought in summer. From late June to mid-August, severe drought occurred in southern Northeast China, southern South China, and northeastern Inner Mongolia.

Drought hit South China in autumn and winter. On 19 November,the areas affected by drought amounted to 462 000 kmin Jiangnan and South China. During early and mid-December, drought persisted in South China, southeastern Jiangnan, and central-southern Yunnan.

3.5. Convective weather events

From March to mid-September, there were 56 convective weather events in China, such as strong wind, hail, tornadoes, and lightning,which was more frequent than the average of the past five years. The convective weather events in northern China mainly occurred from May to June, including strong wind and hail, and those in southern China mainly occurred from July to August, including short-term heavy rainfall and lightning. Convective weather events caused lighter losses than in the past 10 years.

During 17—18 May, hail disasters affected 50 counties in Shandong Province, affecting 595 000 people and 65 000 ha of crops, and damaging about 50 000 houses. The direct economic losses caused by these events amounted to 2.17 billion yuan.

3.6. Low-temperature freezing and snow disasters

In 2020, low-temperature freezing and snow disasters affected 1051 800 ha of crops, and the direct economic losses were 15.41 billion yuan.Compared to the average value of the past 10 years, the direct economic losses in 2020 were light.

During 14—17 February a nationwide cold wave process affected China, with 8°C—14°C of cooling in most areas. Snowfall occurred in Northeast China, eastern North China, and Huanghuai. The maximum snow depth of seven stations in Jilin exceeded 40 cm.

During 17—23 November, heavy snow occurred in North China, with the maximum decrease in temperature exceeding 8°C. Nine counties in Jilin and Liaoning experienced their maximum decrease in temperature on record. On 19 November, snowfall in Kuandian in Liaoning was 81.7 mm, which was more than the normal yearly value (81.0 mm).The accumulated snowfall in local areas of southeastern Heilongjiang,southern and northern Heilongjiang, and central Jilin was about 25—30 mm. The maximum snow depth in Changling in Jilin and Mishan in Heilongjiang reached 38 cm. Snowstorms had negative impacts on agriculture, transportation, and power supply in Northeast China.

3.7. Dust storms in spring

In spring, there were seven dust weather events and two sandstorms or strong sandstorms in northern China. The frequency of dust storms was 10 fewer than normal. The number of dust weather days in northern China was 2.6, which was 2.4 less than normal. During 8—10 March a sandstorm attacked southern Xinjiang basin, which had the strongest intensity in 2020. Tazhong, Qiemo, and Tieganlike in southern Xinjiang suffered strong dust storms. Dust storms had an adverse impact on agriculture, aviation, and air quality in the affected areas.

4. Conclusion

In 2020, both China’s annual mean air temperature and precipitation were above normal. The annual mean air temperature was 10.25°C and the annual precipitation was 694.8 mm, which were the eighth and fourth largest since 1951, respectively. The average temperature in all four seasons was above normal and obviously warmer in winter and spring. The seasonal precipitation in winter, summer, and autumn was above normal, while that in spring was below normal. Regionally, annual precipitation was above normal in Northeast China, the middle—lower reaches of the Yangtze River, North China, Southwest China, and Northwest China, but below normal in South China. The mei-yu season started earlier and ended later than normal, which brought about tremendous precipitation and led to the duration and amount of the mei-yu ranking the highest since 1961.

In 2020, southern China experienced its most severe flood since 1998. Drought occurred frequently in local areas. Convective weather events occurred more frequently in 2020 than the average of the past five years. The frequency of dust storms was 10 fewer than normal. The affected agriculture area and numbers of deaths or missing persons in 2020 were all smaller than in the past 10 years, while the direct economic losses were larger. The losses caused by droughts, typhoons, severe convective weather, low-temperature freezing, snow disasters, and dust storms were all limited. However, the losses caused by rainstorms and flooding were serious.

Funding

This work was jointly supported by the National Natural Science Foundation of China [grant numbers 41875120 and 41605069 ] and the National Key Research and Development Project [grant number 2017YFC1502402 ].

Acknowledgments

The main results of this report are based on the latest climate monitoring status given by the operational system of the National Climate Center of the China Meteorological Administration. We appreciate our colleagues’ hard work on climate monitoring and system developments.We would also like to thank Prof. Xukai Zou, Prof. Jianqing Zhai, Prof.Yanju Liu, Prof. Ge Gao, Prof. Bing Zhou, Dr. Yundi Jiang, Ms Lin Zhao,Mr. Shuai Shi, and Mr. Tong Cui for their contributions.

Disclosure statement

No potential conflict of interest was reported by the authors.