When it comes to white dew, the summer monsoon is gradually replaced by the winter monsoon, and the cold air turns from defense to offense. In addition, the direct sun point moves southward, the sunshine time in the northern hemisphere becomes shorter, the light intensity weakens, and the ground radiation heat dissipates quickly, so the temperature drop rate gradually accelerates.
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The white dew has basically ended the sultry heat of summer, the weather is gradually getting cooler, and the cold brings dew condensation.
The ancients matched the four seasons with the five elements. Autumn belongs to gold, and gold is white. White is used to describe autumn dew, hence the name "Bai Lu".
White dew comes three times and swan geese arrive: After the white dew, the migratory birds that are most sensitive to climate migrate collectively.
The swan geese began to fly from north to south.
The second migratory black bird returns: The black bird refers specifically to the swallow, and the swallow will also fly to the south for the winter.
Three migratory birds feed their shyness: This "shame" is the same as "馐", which is a delicacy.
Raising shame means that birds sense the chilling atmosphere and store food for winter.