The first frost occurs when the sun reaches the longitude of 2 10 degrees every year around Gregorian calendar 10 year10 23rd.
"Twenty-four solar terms" said: "In mid-September, the gas is cold and condensed, and the dew is like frost." At this time, frost has appeared in the Yellow River Basin in China. Thousands of miles of fields, pieces of silver ice crystals are shining, leaves turn yellow and begin to fall.
The ancient book "Twenty-four solar terms" says: "When the frost comes, the yin begins to coagulate." It can be seen that the first frost means that the weather is getting cold and it begins to frost. Meteorologically, the first frost in autumn is generally called "first frost" or "first frost", and the last frost in spring is called "late frost" or "final frost". The interval from the last frost to the first frost is a frost-free period. Some people also call the first frost "Chrysanthemum Frost", because chrysanthemums are in full bloom at this time, and Su Shi, a great writer in the Northern Song Dynasty, said in a poem: "All trees are sweeping away pornography, and only Furong is alone."
Frost is formed by condensation of water vapor, which can only be formed on sunny days. People often say that "the thick frost is fierce" is the reason. Lv Benzhong, a poet in the Southern Song Dynasty, wrote in Luzi IV in the Southern Song Dynasty: "The moon invades the post, and the bridge spends the night frost." Lu You wrote in Frost Moon that "the withered grass is frosty and the cold window is full of new shadows". These poems all show that frost appears on a clear moonlit night in autumn. There are no clouds in the autumn night sky, and there is a lot of heat dissipation on the ground. Water vapor will condense on streams, bridges, leaves and soil, forming tiny ice needles, and some will become hexagonal frost flowers.
The first frost is the last solar term and the coldest solar term in autumn. Once the cold wave strikes, the temperature difference between day and night can reach more than 10 degrees Celsius, so it is a high incidence period of many diseases. Old people are more likely to get sick because of aging organs.
Autumn and winter alternate, and the climate is dry, which is a "dry" season. Dry is the most likely to hurt the lungs and stomach, thus causing gastrointestinal diseases and respiratory diseases. The first frost solar term is the peak of chronic gastritis, recurrent gastroduodenal ulcer and upper gastrointestinal bleeding. In the cold season, most people like to eat hot food, such as hot pot and hot porridge. In particular, some people often use shochu to keep out the cold, add oil to the fire, and increase the stimulation to the gastric mucosa, which can promote the ulcer surface to expand and deepen, and make the condition worse.
Due to the increasing temperature difference between day and night, human blood vessels will contract after being stimulated by cold, which makes blood pressure rise sharply. Therefore, in the first frost season, the incidence of cardiovascular and cerebrovascular diseases, such as myocardial infarction, angina pectoris, cerebral infarction, cerebrovascular accidents and other diseases began to rise. Patients with a history of hypertension should take antihypertensive drugs on time and check their blood pressure regularly to prevent cardiovascular and cerebrovascular accidents. In addition, the elderly are also very prone to "old cold legs" (knee osteoarthritis), and chronic bronchitis is also prone to recurrence or aggravation.
The main points of the first frost solar terms are nourishing yin, preventing dryness, moistening lung and benefiting stomach. The ancients said, "In autumn, you should eat hemp to moisten it." At this time, you should eat more soft foods such as sesame, glutinous rice, japonica rice, honey and dairy products.