Can people shelter from the wind and rain under the big tree in lightning weather? Why?

People usually call lightning clouds Lei Yun. In fact, several kinds of clouds are related to lightning, such as stratocumulus, nimbostratus, cumulonimbus, cumulonimbus, and the most important one is cumulonimbus. Lei Yun in general professional books refers to cumulonimbus clouds.

The process of cloud formation is a process in which water vapor in the air reaches saturation or supersaturation through various reasons and condenses. Water vapor saturation in the air is a necessary condition for cloud formation. The main ways are as follows:

(1) The water vapor content is unchanged, and the air is cooled;

(2) keeping the temperature constant and increasing the water vapor content;

(3) Not only the water vapor content is increased, but also the temperature is reduced.

But for the formation of clouds, the cooling process is the most important process. In the process of cooling, the cooling effect brought by ascending movement is the most common.

Cumulonimbus cloud is a kind of cloud formed in the process of strong vertical convection. Because the ground absorbs much more solar radiation heat than the air layer, the ground temperature rises more during the day, especially in summer. Therefore, due to heat conduction and heat radiation, the atmospheric temperature near the ground rises, the gas temperature inevitably expands, the density decreases, and the pressure also decreases. According to the principle of mechanics, it will rise, and the density of the air layer above it is relatively high, and it will sink. In the rising process, the hot airflow expands and depressurizes, and at the same time, it exchanges heat with the high-altitude low-temperature air, so the water vapor in the rising air mass condenses, and water droplets appear, forming clouds. In the process of strong convection, the fog droplets in the cloud further cool down and become supercooled water droplets, ice crystals or snowflakes, and gradually increase with the height. At the freezing height (-10℃), due to the latent heat released by the freezing of supercooled water, the cloud top suddenly develops upward and spreads horizontally near the tropopause, forming a cloud anvil, which is a remarkable feature of cumulonimbus clouds.

In the process of cumulonimbus cloud formation, positive and negative charges are accumulated in different parts of the cloud under the simultaneous action of atmospheric electric field, temperature difference electrification effect and debris electrification effect. When the charge accumulates to a certain extent, it will discharge between clouds or between clouds and the ground, which is what people usually call lightning.

Lightning has brought great disasters to human society with its great destructive power, especially in recent years, lightning disasters have occurred frequently, and the harm to the national economy has become increasingly serious. It is necessary to strengthen the awareness of lightning protection, actively cooperate with meteorological departments, do a good job of prevention, and minimize the losses caused by lightning.

When human society enters the era of electronic information, the characteristics of lightning disasters are very different from those in the past, which can be summarized as follows: (1) The affected areas have expanded greatly, from the two traditional fields of electric power and construction to almost all industries, with the characteristics of the fields most closely related to high technology, such as aerospace, national defense, posts and telecommunications, computers, electronic industry, petrochemical industry, financial securities and so on. (2) From two-dimensional space invasion to three-dimensional space invasion. The pulsed electromagnetic field, which is transmitted from direct lightning and overvoltage waves to space lightning changes, invades any corner from three-dimensional space, causing disasters everywhere, so the lightning protection project has entered the lightning protection electromagnetic pulse (LEMP) from direct lightning and induced lightning. The former refers to the expansion of industries affected by lightning, and here refers to the expansion of the spatial scope of lightning disasters. For example, on July 25th, 2000 14: 40, a lightning strike caused two units near Guijing Road in Cao Bao Road to be struck by lightning at the same time, instead of the previous lightning strike that only damaged one building. (3) The economic loss and harm degree of lightning disaster are greatly increased. The direct economic loss of the target itself is sometimes not too great, and the indirect economic loss and impact caused by it are difficult to estimate. For example, 1999 At 2 am on August 27th, a paging station was struck by lightning, which caused the station to stop paging for several hours. Direct loss is limited, but indirect loss will greatly exceed direct loss. (4) The fundamental reason for the above features, that is, the key features, is that the main targets of lightning disasters have been concentrated on microelectronic devices and equipment. Lightning itself has not changed, but the development of science and technology has changed the production and living conditions of human society. The application of microelectronics technology permeates all kinds of production and life fields, and the characteristics of microelectronic devices are extremely sensitive, which is easily influenced by the ubiquitous LEMP, leading to the loss of control or damage of microelectronic equipment.

Therefore, the importance, urgency and complexity of lightning protection in today's era have greatly increased, and lightning protection has changed from direct lightning protection to system protection. We must stand at a new height in the historical era to understand and study modern lightning protection technology and improve the comprehensive ability of human beings to defend against lightning disasters.

How does lightning strike cause disaster?

Lightning is a common weather phenomenon in summer, and lightning disaster poses a great threat to natural resources and material civilization created by human beings. So how did lightning cause disaster?

First, lightning produces scorching heat. When lightning strikes, a powerful current passes through the object, generating huge heat instantly. According to analysis, the temperature of lightning current channel can reach 6000℃? 10000℃, sometimes even higher, is enough to melt metal. If the lightning current channel encounters flammable substances, it may cause a fire. For example, from June to August of 1989, oil depots in Jinxi, Qinhuangdao and Huangdao were struck by lightning, which caused fires and explosions in many oil tanks and caused heavy losses. Secondly, the violent shock wave: lightning makes the air near the lightning current channel expand violently and spread around at the speed of ultrasonic waves, and the relatively cold air around it is compressed strongly, and the air expands and contracts to produce violent vibration, which is the shock wave. Affected by shock wave, the lightning current channel and its surrounding environment are similar to bomb explosion, which has great destructive power.

There is also lightning induction, including electrostatic induction and electromagnetic induction, which will produce induced high voltage. For a building, if it is induced by lightning, the internal frame and metal devices with poor grounding are easy to produce sparks, which is very dangerous for the warehouse where flammable materials are stored and will cause an explosion. Finally, indirect lightning strike refers to the physical process of high voltage and strong current between thunderstorm clouds and the earth. When lightning strikes, instantaneous strong current is introduced indoors through transmission cables, communication lines, telephone lines and metal pipes, or electromagnetic induction causes lightning accidents of computer networks, communication equipment and industrial control systems. From the analysis of lightning data in recent years, this kind of accident has a high incidence and serious consequences. Therefore, where there are low-voltage electrical appliances and microelectronic equipment, indirect lightning strikes must be prevented.