The correct way to enjoy the "autumn coolness": first grasp the "personality" of Bailu

Bailu is the fifteenth solar term in the twenty-four solar terms and the third solar term in autumn. It marks the end of the early autumn season and the beginning of the mid-autumn season, reflecting an important node in the temperature changes in nature.

01 How did Bailu get its name?

During the White Dew solar term, you can often see tiny water droplets attached to the green stems, leaves or petals of flowers, plants and trees, making them appear white. Especially under the morning sunlight, they look even more crystal clear and pure white, hence the name "White Dew".

Dewdrops hang from plants at the Alpine Botanical Garden in Shangri-La City, Diqing Tibetan Autonomous Prefecture, Yunnan Province. (Source: Xinhua News Agency)

02 Three "personalities" of Bailu

Without further ado, the "personality" of White Dew can be summarized in two words: cool and humid.

▶Cool: Ranks at the top of the list of temperature differences between day and night throughout the year

After entering the White Dew season, the summer heat gradually subsides and the weather begins to cool down. This is because:

Although the temperature during the day may still be high, the temperature at night will drop significantly, and the temperature difference between day and night will increase. This temperature difference can reach 8℃-16℃, making Bailu one of the solar terms with the largest temperature difference in the year.

The sunshine hours began to shorten, and the daytime exposure time was relatively reduced. This further exacerbated the increase in the temperature difference between day and night, making people feel warm in the sun and cool in the shade.

The cool autumn breeze takes away the summer heat and makes people feel more refreshed and pleasant, especially in the morning and evening, when the coolness is more obvious.

Maple leaves fall in the grass in Dunzhai Town, Jinping County, Qiandongnan Miao and Dong Autonomous Prefecture, Guizhou Province. (Source: Xinhua News Agency)

▶Chao: “Lu” is not called that for nothing

As the temperature drops, the humidity in the atmosphere increases. The temperature drops faster at night, making it easier for moisture to condense into dew, and the air is filled with a strong sense of moisture in the morning.

During the Bailu season, the rainfall increases relatively and the climate is changeable. Some places experience showers and thunderstorms, while other places may experience continuous rainy weather. The rainfall is characterized by low intensity, many rainy days, and often continuous.

In Lotus Lake Park in Nanjing, Jiangsu Province, water droplets hang on leaves after rain. (Source: Xinhua News Agency)

▶Dryness: Autumn dryness gradually rises

We just talked about the humidity, why is it dry again? This is the complex nature of autumn, with a vast area and changeable weather. It is a little humid in the south and a little dry in the north; it is a little humid on rainy days and a little dry on sunny days; it is a little humid in the morning and evening and a little dry at noon; the surface of the earth is a little humid and the atmosphere is a little dry.

Bailu is the third solar term in autumn. Autumn dryness is a general trend. The humidity decreases day by day compared to summer. As the autumn wind gradually rises, people tend to feel dry, which manifests as dry skin, dry mouth, and dry respiratory tract.

Dry mouth and tongue replenish water in time (copyright image of the library, reprinting and use may cause copyright disputes)

03 The “Originator” of the Bailu Climate

(1) Direct sunlight point

As the seasons change, the position of the sun's direct rays on the ground gradually moves southward, the solar radiation received by the Northern Hemisphere gradually decreases, and the intensity of sunshine weakens, causing the ground temperature to gradually drop, forming the cool climate characteristics of the White Dew season.

(2) Winter monsoon

After entering the White Dew solar term, the winter monsoon begins to gradually replace the summer monsoon, and the cold air moves south more and more frequently, causing the ground temperature to drop further, especially at night, when the temperature drop is more obvious.

As the summer monsoon weakens and the winter monsoon strengthens, the cold air brought by the winter monsoon causes the temperature to drop, while also bringing drier air, making it easier for water vapor in the air to condense into dew.

(3) Clouds have poor thermal insulation

During the White Dew season, the nights are often clear and cloudless, which allows the ground to radiate heat into space more effectively. As the thermal insulation effect of the clouds weakens, the ground's radiation heat dissipation accelerates, causing the temperature to drop rapidly at night, causing the water vapor in the air to quickly condense into tiny water droplets when it encounters cold, and attach to the ground or near-Earth objects to form the White Dew.

04 White Dew Precautions

In view of the climate characteristics of the White Dew season, which is gradually getting cooler, with a large temperature difference between day and night and dry air, we must take precautions to ensure the health of ourselves and our families.

◎ Keep warm and protect against cold

After Bailu, the temperature difference between morning and evening is large, so you can carry a coat or scarf with you. Add clothes in time in the morning and evening, especially protect the abdomen, back and feet to avoid cold. The elderly and children should keep warm. When resting at night, make sure the room is warm and cover yourself with a quilt to prevent catching a cold at night.

The temperature difference between morning and evening is large during Bailu, so please add more clothes in time (copyright image of the gallery, reprinting and use may cause copyright disputes)

◎Adjust your daily life

After the White Dew, we should adapt to the seasonal changes in nature, maintain a regular schedule, go to bed early and get up early as much as possible, and ensure adequate sleep time, which will help restore body functions and enhance immunity.

◎Moderate exercise

Autumn is a good time for exercise. You can choose to do jogging, walking, Tai Chi and other exercises to enhance your physical fitness and improve your body's resistance.

Emotional regulation

It is easy to feel sad in autumn, so you should pay attention to adjusting your mood, maintaining a peaceful state of mind, participating in more group activities or communicating with family and friends to relieve stress. You can also relax by reading, listening to music, communicating with friends, etc.

◎Disease prevention

The White Dew season is a high-incidence period for respiratory diseases, such as bronchial asthma and allergic rhinitis . People should pay attention to personal hygiene, wash their hands frequently, avoid crowded places, avoid contact with allergens, and reduce the risk of respiratory diseases. Strengthen indoor ventilation and keep the air flowing. The immunity of the elderly and children is relatively weak and they are more susceptible to seasonal changes. Special attention should be paid to their health and timely care and concern should be given.

◎Skin care and moisturizing

During the White Dew season, the air humidity in many places decreases, which can easily lead to problems such as dry skin and peeling. You should strengthen skin moisturizing and use moisturizing skin care products that suit you to keep your skin hydrated.

◎Pay attention to moisture-proof

In places with continuous rain or heavy precipitation, pay attention to moisture prevention and food mold. Avoid sitting directly on the grass in the morning and evening, as the dew on the grass may wet your clothes.

◎Travel safety

After the White Dew, many places are prone to heavy fog or drizzling autumn weather, which reduces visibility. When traveling, you should pay attention to traffic safety, abide by traffic rules, and avoid traffic accidents.

Author: Wang Yuanhong, Senior Weather and Climate Engineer

Produced by: Science Popularization China