The recent state of northerners: I haven’t been to the south, but I can feel the “humidity and heat” of the south…

□ Popular Science Times reporter Chen Jie and Hu Lijuan

"The temperature has just reached 35 degrees Celsius, but the humidity has exceeded 87%. It feels like being in a sauna as soon as you go out." After the beginning of the dog days, northern regions such as Beijing and Zhengzhou have faced the dual challenges of high temperature and high humidity, making many northerners who are accustomed to dry and hot weather miserable.

Why has the humid and hot weather in the south been spreading to the north in recent years? Why is the humid and hot weather so unbearable?

Cao Yunchang, chief scientist of the Meteorological Observation Center of the China Meteorological Administration, told Science Times that the northward expansion of hot and humid weather is actually an inevitable product of global warming.

Copyright images in the gallery. Reprinting and using them may lead to copyright disputes.

Data shows that in the past 60 years, my country's annual average temperature has risen by about 0.23℃ every 10 years. Most parts of the country are showing a warming trend, especially in the north. "The subtropical high pressure in the western Pacific Ocean that affects my country has moved northward, and the warm and humid air flow in the south can be further transported northward, increasing the water vapor content and precipitation in the north. Therefore, hot and humid weather frequently appears in the north," said Cao Yunchang.

Whether it is humid heat or dry heat, they are actually different combinations of temperature and humidity. Cao Yunchang explained that in high temperature weather of 35℃ or above, humid heat is high temperature accompanied by high humidity, with the relative humidity of the air above 60%, while dry heat is a combination of high temperature and low humidity, with the relative humidity of the air below 50%.

But why does humidity make people feel hotter when the temperature is the same at 35°C?

As we all know, the human body regulates its body temperature mainly through sweating. In a dry and hot environment, the air is relatively dry, and the sweat discharged by the human body can evaporate quickly and take away the heat from the body surface, thus helping the human body maintain a normal body temperature.

In comparison, the hot and humid weather seems a bit "persistent".

"If the humidity increases at the same temperature, the air under the double attack of high humidity and high temperature will seem to be wrapped in a thick layer of water vapor, which will greatly slow down the evaporation rate of human sweat and the body's perceived temperature will increase significantly." Qian Guanyu, director of the Department of Dermatology at the Third People's Hospital affiliated to Jiangsu University, told reporters that at this time, the heat generated by the human body's metabolism, whether it is heat radiation, heat convection or sweat evaporation and other heat dissipation channels, are almost all "blocked".

A large amount of heat trapped in the body cannot be dissipated, which will inevitably increase the burden on the heart, lungs and blood vessels, and then make people feel stuffy from the "heart". "Not only that, hot and humid weather can easily cause health problems such as skin diseases and endocrine disorders, exacerbating the discomfort of the human body," Qian Guanyu emphasized.

It is no wonder that some netizens joked that staying indoors without air conditioning is like "steaming", while going out is like "teppanyaki". Of course, it is not just humans who feel "nowhere to escape". In recent days, some netizens have reported that smartphones have frequently experienced "heatstroke" symptoms such as overheating, freezing, and black screens in hot and humid weather, and all kinds of mobile phone "cooling tools" on the Internet have been sold out.

How should the public respond to the challenges of humidity and heat?

Qian Guanyu's response plan is: when indoors, try to maintain good ventilation and reduce the humidity and temperature of the environment; choose light and easily digestible food, and eat less greasy and spicy food; when going out, try to wear breathable clothes to reduce sweat accumulation and bacterial growth, and replenish water in time to maintain fluid balance.

Cao Yunchang stressed that the public should pay more attention to weather forecasts and take appropriate precautions and preparations according to the situation. "If you are inevitably in a hot and humid environment, you should pay attention to your physical condition in time. If you experience symptoms such as heat stroke, you should seek medical attention immediately."