Basic characteristics of climate resources

There are abundant solar energy resources and great potential for photosynthetic production.

Except for Sichuan and Guizhou, solar energy resources in most parts of China are equivalent to or higher than those in other countries at the same latitude, equivalent to the United States and slightly higher than Japan. The high-value center and the low-value center are between 22 and 35 N, which is the high-value center of the Qinghai-Tibet Plateau. Its southern light energy is close to the most abundant Sahara desert in the world, and Lhasa is known as the "Sunlight City". The low-value center appears in Sichuan basin. In the main agricultural areas of China, there is a lot of photosynthetic effective radiation during crop growth, which provides sufficient light energy for high yield of crops. The growth period of Qinghai-Tibet Plateau is short, and the amount of photosynthetic effective radiation that can be provided for plants is the lowest in China.

The hot zone is subtropical and temperate.

There are many hot areas, and the subtropical and temperate areas are large.

China is the country with the largest number of hot zones in the world. From south to north, tropical zone, south subtropical zone, middle subtropical zone, north subtropical zone, south temperate zone, middle temperate zone and north temperate zone appear in turn. The Qinghai-Tibet Plateau also includes temperate zone, sub-frigid zone and frigid zone. The main agricultural areas in eastern China are large, of which subtropical zone, middle temperate zone and south temperate zone account for 42.5% of the total land area of China, and their heat is similar to that of major agricultural areas in the United States. The accumulated temperature ≥ 10℃ is slightly higher than Japan's 40 N, which is close to the Mediterranean climate zone. In 30 N region, it is 500℃ higher than that in Mediterranean climate region, and 600 ~ 1000℃ lower than that in West Asia, South Asia and Africa.

The remarkable influence of monsoon climate

The seasonal variation of heat resources is very obvious, and there are four distinct seasons in most areas, so agricultural activities are very sensitive to the change of solar terms. Compared with the same latitude areas in the world, Leng Xia is hot in winter in the eastern part of China, and the higher the latitude, the more obvious it is, and the more prominent it is in winter than in summer. Summer is very hot, and annual crops (rice, corn, etc. ) can be planted in the northeast region with higher latitude, which is conducive to expanding the planting area of thermophilic crops and improving the multiple cropping index. However, it is too cold in winter, which makes the planting boundary of overwintering crops or perennial subtropical and tropical economic fruit trees south. This heat characteristic is also one of the reasons for the diversity of planting system in China.

The underlying surface is complex and diverse.

It leads to the redistribution of climate resources, and the mountainous and hilly areas in China account for about 2/3 of the national area. The complex terrain, the trend of large mountains, the ups and downs of the terrain and the distance from the sea have caused the redistribution and combination of light, heat and water resources, making the non-zonal influence in some areas exceed the zonal influence. There is a saying that there are "climate zones" and "different days in ten miles". For example, Qiaojia, Huaping and Yuanmou in the southwest Jinsha River basin are all in the middle subtropical zone, but they have a tropical climate in South Asia. Accumulated temperature ≥ 10℃ is as high as 7000 ~ 8000℃, the average temperature in Leng Yue is above 12℃, and there is basically no frost all year round. Another example is Yunnan, which is located in the low latitude plateau. Because the increase of latitude is consistent with the increase of altitude, in the latitude less than 10 from north to south, hot, warm and cold climates and corresponding vegetation have appeared one after another. Generally, in the alpine region with an altitude of 2300-2500m, cold-tolerant crops are the main crops, and the altitude of 1, 300- 1, 500m is in the middle temperate zone, which is a triple cropping area for one or two years; The area below1300m is low tropical, and it is a double cropping or triple cropping area. Some east-west or northeast-southwest mountains in China have a significant barrier effect on cold air from the north and warm and humid air from the south, which is a watershed with significant differences in water and heat conditions on both sides of the mountains. For example, the average annual temperature difference between the banks of Daxinganling is 2 ~ 4℃, the cumulative temperature difference is 300 ~ 1000℃, and the annual precipitation difference is 100 ~ 200mm, which is the transition zone from agricultural areas to pastoral areas. Tianshan Mountains have become the natural dividing line between arid south temperate zone and arid middle temperate zone in Xinjiang. The Qinling-Bashan Mountain area is the dividing line that marks the climate in the north and south of China, and it is also the dividing line with zero water balance. It marks the combination of dryland agriculture in the north and paddy agriculture in the south, and it is also the dividing line between whether crops overwinter or not. In particular, the blocking effect of mountains makes the winter warming in Sichuan Basin very significant. The monthly average temperature in 65438+ 10 is 3 ~ 4℃ higher than that in the eastern plain of the same latitude, the accumulated temperature ≥ 10℃ is 300 ~ 500℃ higher, and the frost-free period is 40 ~ 60 days. If the warming effect is corrected by altitude, it is equivalent to moving the Sichuan Basin south by five latitudes. The heat resources in mountainous areas change obviously with altitude. Generally, with the increase of altitude 100 meters, the annual average temperature will drop by 0.5 1℃, and the accumulated temperature ≥ 10℃ will drop by 170℃, and the growth period will be shortened by about 4 ~ 6 days.

Thermal effect of special terrain

You can't ignore it. For example, some slopes in subtropical mountainous areas have inversion temperature in winter, and there are many warm zones and warm communities; Some large water bodies (lakes and reservoirs) can regulate the temperature around them, which is beneficial for fruit trees and crops to avoid cold and winter. On the other hand, in the low concave terrain, cold air is easy to accumulate at the bottom of the valley, forming a "lake" of cold air, which makes crops vulnerable to freezing injury.

Uneven distribution of precipitation resources

The dry-wet boundary is close to the isoprecipitation line. Compared with the whole world, the precipitation in China is not abundant. Roughly estimated, the average annual precipitation in China is about 648 mm, which is about 19% less than the global average annual precipitation of 800 mm and 12% less than the Asian average annual precipitation of 740 mm. The annual precipitation in parts of Japan and North Korea at the same latitude is more than that in China. The main water vapor of precipitation in China comes from the Pacific Ocean, and the distribution trend of annual precipitation is decreasing from the southeast coast to the northwest inland, and the isohyet generally shows northeast-southwest trend. According to this trend, the annual precipitation isoline of 400 mm is equivalent to the dividing line between semi-arid and semi-humid areas; The isoline of 250 mm annual precipitation is close to the dividing line between drought and semi-drought; The 900 mm annual precipitation isoline across the east is the dividing line between the semi-humid area and the humid area in the east.

The regional distribution of precipitation is extremely uneven. Northwest inland basin accounts for 36.4% of China's total area, with an average annual precipitation of only 65,438 0.64 mm and an annual total precipitation of only 9.5% of China's total. The outflow basin in southeast China accounts for 63.7% of the country's total area, with an average annual precipitation of 896 mm, and its annual total precipitation accounts for 90.5% of the country.

China has more precipitation in summer and less precipitation in winter, which is an important feature of monsoon climate. The seasonal distribution of precipitation varies greatly from place to place, especially in the north, where the rainy season is short and the precipitation is obviously concentrated in summer. Therefore, taking seasonal water transfer measures is one of the important countermeasures for drought relief.

Rain and heat are basically the same season.

In summer, light, heat and water are favorable, and the climate production potential is basically synchronized with the seasonal changes of temperature and precipitation in most areas, which is the advantage of agricultural climate resources. In summer, it is hot and rainy, and the discharge of photosynthetic effective vehicles is large, which provides very favorable conditions for the vigorous growth of plants and has great potential for climate production. The rain and heat conditions in different places in the same season are different. In northern China, the temperature rises rapidly in spring and is very high in summer. The accumulated temperature ≥ 10℃ from June to August accounts for more than 50% of the whole year, and the precipitation accounts for more than 60% of the whole year. The accumulated temperature and precipitation of ≥ 10℃ from June to August in Jianghuai and its south area account for 30 ~ 40% of the whole year, with long rain and heat in the same season and high multiple cropping index. In Yunnan and Qinghai-Tibet Plateau, the temperature changes gently in a year, the precipitation concentration is higher than the temperature concentration, and the coordination of water and heat is slightly poor. For example, the accumulated temperature in Yunnan from June to August only accounts for 20-30% of the whole year, while the precipitation in the same period accounts for more than 60% of the whole year. The accumulated temperature of the Qinghai-Tibet Plateau from June to August accounts for 55-65% of the whole year, and the precipitation in the same period accounts for 60-80% of the whole year.

Heat and precipitation vary greatly from year to year, which is prone to low temperature chilling injury or drought and flood disasters. According to the research of the famous meteorologist Mr. Zhu Kezhen, in the long history of 5000 years, there have been many cold periods and warm periods in China, which made the boundary between agriculture and animal husbandry move back and forth from north to south; The change of climate change in historical period also caused the change of planting boundary of single and double cropping rice from north to south in two latitudes. In the past century, the accumulated temperature of ≥ 10℃ in China fluctuated periodically for 7-8 years and 2-3 years, especially for 8 years. At the beginning of this century, the accumulated temperature in various places was less, which began to increase in the mid-1930s, reached the highest in the 1950s, and then gradually decreased. In the mid-1960s, there was a brief warming process, and now it oscillates around the average value. In recent 30 years, the differences of heat status between the warmest year and the coldest year are as follows: the accumulated temperature ≥ 10℃ is about 500 ~1100℃; The number of consecutive days ≥ 10℃ varies from 30 to 60 days. The relative variability of accumulated temperature ≥ 10℃ (the annual average of the absolute value of accumulated temperature anomaly as a percentage of the average accumulated temperature) is 4-5% in Qinghai-Tibet Plateau, more than 3% in Northeast China, North China and Northwest China, and less than 1.5% in South China and South Yunnan. Unstable heat resources will lead to unstable agricultural production. For example, the average deviation of accumulated temperature between high temperature year and low temperature year in Heilongjiang Province is about 300℃, which can increase or decrease the output by about 30%.

Problems and challenges

Various climate types have created rich ecosystem types and various types of climate resources utilization in China. However, on the issue of using China's climate resources to promote China's sustainable development, we also have to see the following remarkable features.

First, because of China's continental climate, the cold and water shortage in the vast northern region often become the limiting factor of biological production, so the abundant light energy resources and land resources are not fully utilized, which restricts the improvement of land productivity and even the further development of economy and society in China.

Secondly, climate change is not only an increase in temperature, but also an increase in the frequency and intensity of extreme weather events.

The research shows that the future climate change will lead to an increase in the annual variability of summer monsoon precipitation in the north, which means that the northern hemisphere monsoon climate zone may suffer from extreme weather events such as floods and droughts with greater probability and intensity. Most areas in China are in the monsoon climate zone, and the advance and retreat of the monsoon directly affects the flood and drought disasters in China and has a negative impact on the development of the national economy. East Asian monsoon, southeast monsoon and southwest monsoon have great influence on summer precipitation in China, and their variation will inevitably lead to the increase of climate disaster losses in agricultural production in China, and the possibility of stable improvement of production level will be greatly reduced.

Therefore, the uncertainty of climate change, especially the adverse impact of climate change on China's social economy and ecological environment, or even a catastrophe, directly affects the sustainable development of China, and even poses a threat to some extent.

Thirdly, China's infrastructure and ability in climate system detection and fine observation of climate elements, as well as the infrastructure to deal with climate change, are still far behind the world's advanced level, which is obviously not enough to support China's ability to achieve sustainable development. The existing professional meteorological observation network can not meet the needs of developing professional services in various fields of economy and society in terms of detection range, elements, accuracy and resolution. The scientific content of technical equipment is not high, and the observation means and equipment are backward; The observation items are not targeted and the norms and standards are not uniform. There are some overlaps and gaps, such as the lack of observation data in ocean, desert and mountainous areas and transportation industry. The field of observation needs to be expanded and integrated. For example, sub-meter wind field observation has not been carried out in areas rich in wind resources in China, which can not provide fine climate data and meteorological support services for the development of wind resources.

China's ability to predict extreme weather and climate events with high temporal and spatial resolution, such as hail, heavy rainfall, strong storm and blizzard, still has obvious shortcomings and defects. In view of the above characteristics, we should make rational use of China's climate resources, strengthen scientific research on climate change and its impact, and enhance and improve the ability of climate science to ensure China's economic and social development.