Climate Changes of 24 Solar Terms in the Middle and Lower Reaches of the Yellow River during 1961-2010

Ancient Chinese farmers created 24 solar terms to guide agricultural production, improve the quality and level of meteorological services, and prevent and treat human diseases. Under the background of global warming, the variation characteristics of six meteorological elements of the 24 solar terms such as temperature, humidity, and wind speed, etc. during 1961-2010 are analyzed in the middle and lower reaches of the Yellow River region. It is determined that climate change is significant in the study region. The Great Heat and Slight Heat include high temperatures and humidity; the Great Cold and Slight Cold include low temperatures and humidity; the Clear and bright includes various temperature with wind; and the Frost's Descent includes gradually cooling with aggravated autumn dryness. During the 50 year study period, the mean, maximum, and minimum temperatures of the spring-type solar terms have increased significantly whereas only the minimum temperatures of the winter-type solar terms show the same increase. The pressure distribution shows significant increases in summer- and winter-type solar terms. In addition, relative humidity and precipitation show decreasing trends, with the autumn-type solar terms showing the most obvious decrease. The wind speed of all solar terms shows a decreasing trending, with the maxima in spring and minima in summer and autumn. Sunshine hours of summer- and winter-type solar terms show decreasing trends.