Source: China Meteorological News Agency
Release date: July 29, 2010 at 10:56
Intern reporter of China Meteorological News Sun Nan Anjia
Hot! With the arrival of the dog days, the high temperature in the whole country has come back again. On July 26th, the Beijing Meteorological Observatory issued the yellow warning signal of high temperature again. The citizens in Beijing complained: "The highest temperature in the weather forecast is only 35℃, but it feels like it is almost catching up with the high temperature of 40℃ a few weeks ago!"
Why is there always a gap between the temperature people feel and the temperature predicted by the meteorological department? Is the data monitored in the louver box discounted to the temperature?
Record the history of air temperature
The standard temperature is measured in the louver.
Taking the pulse for the sky is a scientific and rigorous work. Li Xiaoquan, the chief expert of China Weather Network and former director of the Central Meteorological Observatory, told us that there are strict standards for the setting of louver boxes, which are set according to the regulations of the World Meteorological Organization and the norms of meteorological observation.
The thermometer should be erected at a height of 1.5 meters from the ground and installed in a louver box with ventilation on six sides. It should not only ensure that it can communicate with the outside air, but also ensure that it will not be excessively affected by the wind, and at the same time avoid direct sunlight. In addition, the environment around the louver box also has strict requirements. It is internationally unified that the observation field must be empty and flat, and there should be no trees and tall buildings around it, and it should be placed on the lawn with a thickness of no more than 20 cm.
Only in this way can we ensure that the global meteorological observation data are representative, accurate and comparative, facilitate the global sharing of temperature data, correctly analyze the changes of weather systems and provide reliable weather forecasting services.
Every day, at a fixed time, observers should observe the temperature of the louver. Stations that switch to automatic meteorological observation will also regularly transmit observation data to forecasters for weather analysis and forecast.
Li Xiaoquan said that the temperature forecast mentioned in the weather forecast refers to the forecast of air temperature. The air temperature is very local, which is related to altitude and surrounding environment. Human activities are generally at the height of 1 meter to 2 meters. Therefore, the air temperature in the 1.5-meter-high louver box can reflect the real atmospheric situation of the human activity layer, which represents the undisturbed standard air temperature in the natural state.
Different feelings under the same sky
The difference of somatosensory temperature caused by many influences
The somatosensory temperature refers to the temperature that people feel. Due to the differences of regions, environments and individuals, there is a gap between the somatosensory temperature and the actual temperature.
There are many factors that affect the somatosensory temperature. Li Xiaoquan thinks that the most important factors that make people feel the temperature difference are relative humidity and wind power.
When the temperature is high and the humidity is high, the sweat on the skin surface cannot evaporate well, so the heat dissipation efficiency of the human body is low, and the somatosensory temperature is higher than the actual temperature. So even in the hot weather of 35℃, as long as the humidity is low, you will feel dry and not too uncomfortable. However, in most cities in the south and in the rainy season in the north, the relative humidity will reach more than 80%. At this time, as long as the temperature exceeds 32℃, the human body will feel sultry and unbearable.
Wind, like a huge fan, virtually accelerates the flow of air, and can quickly take away sweat from human skin, making people feel as if the temperature has dropped. In addition, the influence of solar radiation is also very obvious. Under the same temperature, humidity and wind speed, the temperature difference between sunlight and the somatosensory temperature in the shade can be 4℃ to 6℃.
The somatosensory temperature also varies from person to person: people in different regions feel different. Indian tourists who are used to the high temperature of 45℃ will not feel very hot when they come to China to see the Expo, but tourists from cold northern Europe are hard to adapt. Even in the same area, the feelings of the elderly and children will be very different. Even two adults in the same area will feel different when standing in the sun. Physical condition, clothes color, skin color and even good or bad mood can affect people’s feeling of temperature. As the saying goes, "being calm and naturally cool" is a good portrayal of the influence of people’s emotions on somatosensory temperature.
In the new round of high temperature, the public clearly felt the difference between the somatosensory temperature and the real temperature, and some people started the experiment of frying eggs with manhole covers. Crack, crack, crack, crack, crack, crack, crack, crack, crack, crack, crack. Under the direct sunlight, the asphalt road was baked with oil. Some people took out a thermometer to measure the ground temperature, which actually reached 70℃ to 90℃. Many netizens suspected that not predicting the road temperature was for fear of unnecessary panic caused by excessive temperature.
In this regard, Li Xiaoquan explained that the temperature should be representative, and the temperature of different underlying surfaces is different. It is a universal standard method to observe the ground temperature by burying the thermometer half in the soil. The meteorological department has a record of monitoring the surface temperature, but predicting the ground temperature in summer has little practical significance for citizens’ travel activities. Regardless of the ground temperature, people should choose to walk with shoes.
Thermal index forecast for weather "cooling down"
Humanized service reminds people of sun protection and heatstroke prevention
Meteorology affects all kinds of human activities everywhere. As people pay more and more attention to meteorology, the task before meteorologists is not only to talk to the sky, but also to talk to people.
Li Xiaoquan believes that meteorological departments in various regions should provide the forecast of somatosensory temperature index according to local people’s living habits, topography and landforms, not necessarily as accurate as the live temperature, but at least should distinguish grades. "I think the weather forecast in the future will tell people whether the weather tomorrow will be dry, comfortable and hot, sultry or very sultry, not just the dry’ maximum temperature of 35℃’."
At this year’s World Expo, the heat index forecast of the Expo site, which has been prepared for nearly a year, was launched on Shanghai Weather Online in many languages. Thermal index forecast of Expo site: Shanghai model 34, German model 39, Hong Kong model 33 … Shanghai Meteorological Bureau introduced internationally famous thermal index forecast models. This thermal index forecast product is released regularly twice a day.
Geng Fuhai, head of the Urban Environment Center of Shanghai Meteorological Bureau, said that the thermal index is an index describing human comfort. Use the thermal index calculation models of various countries to calculate the possible somatosensory temperatures of people in various countries. For example, the actual temperature is 33℃, the Shanghai model shows a thermal index of 34, the American model shows a thermal index of 120, and Americans know that it is 120 degrees Fahrenheit at a glance.
Ms Guan, a tourist visiting the Expo from Anhui, said: "The introduction of the heat index is very humanized. Although the weather has been sultry for several days, I feel very happy when I go online to see the meteorological service in the Expo Park before going out every morning."
"Although the thermal index has been launched, the relevant verification issues are still being discussed internationally. The somatosensory temperature is influenced by personal factors, and everyone has differences, so the operation of this model is difficult to be accurately verified. " Yan Fuhai said.
Tang Xu, director of the Shanghai Meteorological Bureau, also said that the meteorological forecast service is not only the Expo meteorological service, but also provides the internationally accepted standard temperature forecast, and also provides various refined products according to the needs of various units in the city and the feelings of pedestrians on the road. Tang Xu said: "our work should keep pace with the times and meet the needs of the broad masses of the people. This is the direction of our efforts. Meteorological standards should be adhered to, but follow-up services should also be strengthened. "
Weather can also make life better. "People-oriented" is not only the ruling idea, but also the proper meaning of the meteorological department’s continuous improvement of public service level. Just as Li Xiaoquan said, under the premise of doing a good job of live temperature forecast, the forecast of somatosensory temperature index can make meteorological services icing on the cake.
(Editor: Luan Fei)
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