STUDY IN CHINA GLOBAL (SCG)The Moon on a Cold Night
霜月
by Li Shangyin
（唐）李商隐
“When people can hear the sound of wild geese, the cicada stops tweeting;
初闻征雁已无蝉，
I climb up to a high building and look far into the distance, seeing the water and sky merge into one;
百尺楼高水接天。
The deity of snow and frost, Qing Nv, and the goddess of the moon, Chang’e are not afraid of the cold;
青女素娥俱耐冷，
They are still competing with each other to see who is more beautiful.”
月中霜里斗婵娟。
Interesting Meteorological Knowledge in Proverbs
First, “Heavy frost brings sunny weather” and “When there is frost, there usually will be a sunny day.”
These two proverbs straightforwardly present the relationship between frost and sunny weather. But in fact, it’s not always like that. The frost mentioned in those proverbs refers to radiation frost, caused by cold high. Under the control of cold high, there are more downward currents of air. There fore, the sky at night is clear and the moon is bright and the next day is sunny.
Second, “Snow falls onto high mountains, while frost falls on low-lying land.”
These two proverbs have shown that there tends to be snow on high mountains and frost on low-lying land. But the question is, why does this happen?
We all know that the higher the place, the lower the temperature. For of this reason, when the temperature near the ground is still above 0℃, the temperature on high mountains is already below 0℃.
Clouds are hundreds or even thousands of meters away from the ground, so the temperature around and in the clouds must be lower than that of the ground. The water content inside the clouds forms into snow due to the low temperature there. Then snow begins to fall downward, it melts gradually and finally melts into raindrops when it reaches the ground. Sometimes the snow hasn’t melted when it reaches high mountains, so there is snow up there.
As for why there is frost on low-lying ground, this also relates closely to temperature. We all know that the lower the temperature, the greater the density. In this case, the coldest and heaviest air always goes to the lowest places. When the air reaches there, it will stay and condense into frost.
Third, “Just one frosty morning can’t ensure a long period of sunny days.”
We have said that frost is controlled by the dreaded cold high, which is common in spring and autumn. No matter what kind of frost it is, the strength of the frost and cold air relate closely.
“Just one frosty morning can’t ensure a long period of sunny days” shows that cold air is not very strong and the temperature is not very low and quick to move away. Therefore, the cold air moves somewhere else, and after bringing one frosty morning, the place will be under the control of low air pressure, and the weather will turn bad.
However, if there are continuous frosty mornings, this shows that the cold high is very strong and stable and moves slowly. In that case, the sunny weather can last for a few days or a week.
Shanxing
山行
by Du Mu
（唐）杜牧
Going up to the top of the cold mountain along meandering pathways,
远上寒山石径斜，
I see a few houses hidden among the clouds.
白云生处有人家。
I stop my carriage to enjoy the beautiful scene of red maple forests,
停车坐爱枫林晚，
The maple leaves seem redder than flowers in February.
霜叶红于二月花。
This poem means the poet is very fond of maple leaves. It means enjoying the scene is even more important than going on with his journey. The pathway, the maple forest, the white clouds and the households hidden among the clouds form a beautiful autumn picture.
Hebei Province: It’s time to harvest soybeans and plant late season wheat in the Frost’s Descent period. People plant more spinach and rape to bring an early harvest next spring.
Xinjiang Province: The weather turns cold in October due to the arrival of Cold Dew and Frost’s Descent. Frost appears in early October in northern Xinjiang, and during the Frost’s Descent period in southern Xinjiang.
Jiangsu Province: There is no green (unripe) rice in Cold Dew and harvests should be done during Frost’s Descent.
Anhui Province: Harvests should be finished by Cold Dew and it’s time to turn the soil during Frost’s Descent.
Hunan Province: When Frost’s Descent comes in October, it’s time to harvest late season rice and sweet potatoes.
Fujian Province: Cold Dew and Frost’s Descent both come in October, and rice becomes ripe. It’s time to store plenty of fertilizer and prepare for winter planting.
Talking about the Phase without Frost
People usually call the last frosts of spring the “final frost” and the first frosts of autumn the “first frost”. The phase without frosts refers to the period between the “final frost” and “first frost.”
Due to China’s huge size, the length of the phase without frost varies from province to province. Most parts of China lie in the North Temperate Zone, so frost happens in all parts of the country except some parts of Hainan Island, Yunnan Province, Taiwan Province and the islands in the South China Sea. According to statistics, the “first frosts” appear in mid-September in Northeast China and the “final frost” happens in late April. The phase without frost lasts less than 150 days. For the North China areas, “first frost” happens in late October and the “final frost” in early April, with a 200-day phase without frost in between. The phase without frost is about 250 days long in the Yangtze River regions and more than 300 days long in South China.
The duration of the phase without frost is related to the length of the cold season in the area. In other words, places with long cold seasons also have long phases without frost.
