Abstract:

Different relationships between precipitation and temperature have different impacts on water resources, vegetation, and agricultural production; however, there is still a lack of understanding of the relationship between the two factors and their spatiotemporal variability across a wide range of climate typologies. This paper focuses on the relationship between precipitation and temperature observed in northern China (northern China encompasses a vast area that stretches over a great distance in both the latitudinal and longitudinal directions; the total area is approximately 531×10⁴ km², and it consists of three regions: the northwest region, which includes Qinghai, Gansu, Ningxia, Shaanxi, western Inner Mongolia, and Xinjiang; the northern region, which contains Hebei, Shandong, Henan, Shanxi, and central Inner Mongolia; and the northeast region, which consists of Heilongjiang, Jilin, Liaoning, and eastern Inner Mongolia. Northern China has complex and varied landforms, with various climate types. There are significant differences in surface relief, temperature, and precipitation between the western and eastern regions of northern China). Annual (and monthly) data (including the average minimum temperature, average temperature, average maximum temperature, and precipitation) were collected at 357 meteorological stations distributed over northern China and its surrounding regions from the time of the establishment of the stations to 2018. The data were obtained from the National Meteorological Information Center of the China Meteorological Administration. The National Meteorological Information Center of China has conducted quality control on the temperature data collected at all meteorological stations. Thus, these data are reliable and contain no notable abrupt change points or random variations but instead have relatively uniform and consistent variations, and they therefore can represent the climate conditions in the study area over northern China and its surrounding regions. By adopting several statistical methods, including the central cluster method, this study reveals the relationship between precipitation and temperature in both qualitative and quantitative forms. The results indicate that the precipitation and temperature in summer showed the highest correlation, followed by autumn and winter, whereas spring showed the lowest correlation between these variables. The precipitation was negatively correlated with the average temperature and the average maximum temperature in each season, whereas it was positively correlated with the average minimum temperature. The relationships between precipitation and temperature can be divided into four classes: warm-dry, warm-wet, cold-dry, and cold-wet. Under this classification system, the majority of the area under consideration in the 1950s was classified as cold-dry or cold-wet. In the 1960s, the coverage of cold-dry and cold-wet gradually withdrew to the west, and warm-dry and warm-wet began to become the main classes in northeast China and other regions. After entering the 1970s, the dominant relationship between precipitation and temperature could be classed as warm-wet and warm-dry, and this classification is still valid to this day. After the turn of the 21^st century, the cold-wet and cold-dry relationship reappeared in the northeast and other isolated regions, with the largest coverage during the winter. This work outlines research regarding the relationship between precipitation and temperature and provides a reference for the improvement of the regional ecological environment and the response to water resource problems.

Key words: precipitation, temperature, seasonal relationship, spatiotemporal variability, northern China