After the "explosive warm weather", the cold wave "returns" again! A bit unprepared? Please check out this dressing rule →

In recent days, many parts of the country have experienced an "explosive warming" in weather. Some areas in the south are even as hot as summer. Just when people are about to take off their thick clothes, the cold wave comes "knocking on the door" again.

The Central Meteorological Observatory continued to issue a yellow warning for cold waves at 18:00 on March 1: Affected by the cold wave, it is expected that from 20:00 on March 1 to 20:00 on March 4, the temperature in central and eastern my country will drop by 6-10℃ from north to south, among which the southern part of North China and most areas to its south will drop by 12-16℃, and some areas will drop by more than 18℃; on the morning of the 4th, the minimum temperature of 0℃ will be pushed south to the area from Jianghan to Yanhuai. In addition, the northern and western parts of the Qinghai-Tibet Plateau will drop by 6-10℃.

Among them, it is predicted that from 20:00 on March 1 to 20:00 on March 3, the central and eastern parts of Northeast China, the central and southern parts of North China, Huanghuai, Jianghuai, Jianghan, central and western Jiangnan, northern South China, and northern and western Qinghai-Tibet Plateau will drop in temperature by 6-8°C. Among them, parts of eastern Jilin, southern North China, central and western Huanghuai, Jianghan, and western Jiangnan will drop in temperature by 10-14°C, and the local temperature drop may reach more than 16°C.

Image source: China National Meteorological Administration

Why does the temperature in spring fluctuate like a roller coaster? Sometimes it's freezing cold, and sometimes it's scorching hot. How should we deal with it?

01Why is the temperature in spring like a naughty child?

( 1 ) Frequent cold air activities

Spring is the transition season from winter to summer. Although the cold air gradually weakens, it still moves south from time to time. When strong cold air strikes, the temperature drops rapidly.

( 2 ) Intensification of warm and humid air currents

As the sun's direct point moves northward, the warm and humid air currents from low latitudes continue to gain strength and advance northward. When the warm and humid air currents meet the cold air, the two forces are equal, and a front is formed. Near the front, the weather changes are complex and the temperature fluctuates significantly.

( 3 ) Changes in the westerly circulation

In spring, the atmospheric circulation in the westerly belt is in the stage of adjustment and conversion. The atmospheric circulation in the mid- and high-latitudes may change from being controlled by high pressure to being influenced by low pressure systems, or vice versa. When the high pressure ridge controls, the weather is clear, the solar radiation is strong, and the temperature rises; when the low pressure trough or cold vortex moves in, the temperature drops.

( 4 ) Subtropical high pressure moves northward

The subtropical high pressure gradually moves northward in spring, and the warm and humid air flow at its edge is transported northward, which can increase the temperature in central and eastern my country. However, the position and intensity of the subtropical high pressure are not stable. When it retreats or weakens, the warm and humid air flow weakens, and the temperature may drop accordingly.

( 5 ) Changes in solar radiation angle

In spring, the sun's direct point gradually moves northward, the solar radiation received by the ground gradually increases, and the daytime temperature rises. However, since the solar altitude angle has not yet reached the maximum value in summer, the heat received by the ground is limited, and the angle and duration of solar radiation received in different regions vary greatly, resulting in complex temperature changes.

( 6 ) Differences in surface heat absorption and heat dissipation

The specific heat capacity of land and ocean is different. Land heats up and cools down quickly, while ocean heats up and cools down slowly. In spring, the land and ocean are heated differently. Temperature gradients are easily formed at the junction of land and sea or in different underlying surface areas, which promotes changes in air flow and weather systems, leading to temperature fluctuations.

( 7 ) Vegetation has limited regulatory effects

The vegetation in spring is not yet fully lush, and its regulating effect on the atmosphere through photosynthesis is weak. The energy distribution in the atmosphere is not uniform enough, making it difficult to effectively buffer changes in temperature, making it more likely for the temperature to fluctuate significantly.

In addition to the above reasons, under the background of global climate change, the instability of the climate system has increased, extreme weather events have occurred frequently, and the deviation of temperature from the average temperature has increased, making the fluctuation of spring temperature more obvious. Greenhouse gases emitted by human activities and changes in land use will change the composition and properties of the atmosphere, affect atmospheric circulation and heat balance, and increase the complexity and uncertainty of spring temperature changes.

Knowledge expansion : The impact of " explosive warmth " on the human body

The sudden rise in temperature in spring has a significant impact on the human body, mainly manifested in:

(1) The human body's blood vessels will dilate and the blood flow rate will change, which may induce blood pressure fluctuations . For patients with hypertension, they will experience uncomfortable symptoms such as dizziness and fatigue.

(2) Viruses and bacteria become more active, and the human respiratory mucosa becomes more fragile , making it more susceptible to colds, fevers, lung infections , and other symptoms. The body's immune system is activated, triggering an inflammatory response, which increases the heart's pumping burden and interferes with the normal regulation of the cardiovascular system.

(3) Plants grow vigorously in spring, and allergens such as pollen and catkins increase . A sudden rise in temperature may cause these allergens to be released in large quantities. People with allergies are prone to allergic reactions such as runny nose, sneezing, and rash after contact.

(4) The intensity of ultraviolet rays also increases, and the skin's tolerance to ultraviolet rays has not yet adapted, which can easily cause spring dermatitis .

(5) It affects the body’s biological clock and endocrine system , which may cause emotional instability, irritability, anxiety , etc.

(6) The body's metabolism speeds up, blood circulation on the body's surface increases, and blood supply to the brain decreases, making it easy to experience "spring fatigue" symptoms such as drowsiness, fatigue, and lack of energy .

Image source: China National Meteorological Administration

03 “ Peeling the Onion ” Dressing Method

How should we dress in the face of the fluctuating temperatures in spring? There is a way of dressing called "onion dressing" - just like peeling an onion, wear clothes in layers. This way of dressing can easily add or remove clothes according to different temperatures and environments, so that the body always stays comfortable and avoids catching a cold or overheating due to temperature changes. The specific method is as follows:

When you go out in the morning, the temperature is lower, so you can wear three layers of clothing to keep your body warm;

As the temperature rises during the midday, you can remove your outer layer and even your mid-layer clothing;

When the temperature drops in the evening, you can put on the clothes you took off to effectively cope with the large temperature fluctuations during the day.

04 What clothes should you choose for each layer of "onion skin"? There are also skills

Inner layer : Choose soft, breathable, sweat-absorbent materials, such as cotton or bamboo fiber underwear. These materials can quickly absorb sweat from the skin surface, keeping the skin dry, making the body feel comfortable even when the temperature rises and the body sweats, and preventing colds caused by sweat soaking the clothes.

Middle layer : Choose clothes with good warmth retention , such as thin sweaters, fleece clothes , etc. These clothes can provide good warmth retention when the temperature is low, and when the temperature rises and you need to reduce the clothes, you can easily take them off without affecting the overall wearing effect.

Outer layer : Wear a windproof and waterproof coat, such as a windbreaker, jacket or thin cotton coat . The weather in spring is changeable and there may be wind and rain. The outer layer of windproof and waterproof coat can effectively block the cold wind and rain and protect the body from the external environment. When the sun is shining and the temperature is high, you can unbutton or take off the coat and only wear the inner and middle layers.

In addition to the onion-style dressing method, you can add scarves, hats, gloves, shawls and other accessories as needed on the basis of wearing basic clothes. When the weather is cold, wearing thick scarves, woolen hats and gloves can effectively reduce heat loss; when the temperature is slightly higher, you can choose thin silk scarves or shawls, which can not only play a certain decorative role, but also keep you warm when the temperature difference between morning and evening is large.

Author: Wang Yuanhong, Senior Weather and Climate Engineer, Member of the Chinese Writers Association

Reviewer: Tang Qin, Director of the Science Popularization Department of the Chinese Medical Association, National Health Science Popularization Expert

Produced by: Science Popularization China