A little knowledge of meteorology

According to statistics, the month with the strongest cold air in China is 1 1. From June to February in 5438, the average temperature in most parts of the north was between _ 5℃ and _ 20℃, and frost sometimes appeared after the strong cold air in the south.

2. heavy snow

Strong cold air can often form large-scale snowfall or local blizzard. Snowfall has many benefits, especially for relieving winter drought and freezing farm diseases and insect pests. However, the snowy road is slippery and icy, which easily leads to civil aviation flight delays, road traffic accidents and lane congestion; In some areas, snow storms and road closures will also pose a threat to the safety of people and animals in pastoral areas.

3. freezing rain

Freezing rain is snow falling from the upper cold layer, sometimes it melts into rain in the middle layer, and becomes supercooled water with raindrops at a temperature below 0℃ in the lower cold layer. The supercooled water drops fall from the air, reach the ground and touch anything on the ground, and immediately freeze to form freezing rain. When freezing rain occurs, uneven ice shells appear on the ground and objects, which will have a great impact on traffic, electricity and communication, and will also cause damage to fruit trees.

4. Frost

Rime is the milky white ice crystal precipitation formed on objects by direct condensation of water vapor in the air at low temperature or direct freezing of supercooled water droplets. There are many foggy days in winter in China: Heilongjiang, Jilin, northern Xinjiang and northern Shaanxi. Rime is a kind of natural beauty that people generally appreciate, but sometimes it will become a natural disaster, which will seriously break wires and trees and affect traffic, power supply and communication.

5. Heavy rain

The formation process of rainstorm is quite complicated. Generally speaking, sufficient and continuous water vapor, strong and lasting upward movement of airflow and instability of atmospheric structure are the main physical conditions for heavy rain.

The favorable combination of various scales of weather system and underlying surface, especially topography, can produce heavy rain. The main weather systems that cause large-scale rainstorm in China are fronts, cyclones, shear lines, eddies, troughs, typhoons, easterly waves and intertropical convergence zone. In addition, thermal thunderstorms will also cause short-term and small-scale heavy rains in arid and semi-arid areas.

Extended data:

1. The dew in the morning is usually clear.

Why is it usually sunny when there is dew? This is because on a clear and cloudless night, the ground dissipates heat quickly, the field temperature drops rapidly, and the tolerance for water vapor in the air weakens, so that water vapor condenses on grass leaves and stones one after another. On a cloudy night, the ground seems to be covered with a big quilt, so the heat is not easy to dissipate, the temperature does not drop, and the water vapor stored in the cold is not easy to condense into dew.

There is always a rainbow after the rain.

In the air after a heavy rain, there are many small water droplets floating in the air. They are like prisms hanging in the air. When sunlight passes through them, it is first decomposed into seven bands: red, orange, yellow, green, cyan, blue and purple, and then reflected back. At this time, if someone stands between the "rain curtain" formed by the sun and raindrops, they will see colorful rainbows.

It usually snows in winter.

Winter is coming, why does it snow? This is because the temperature is low in winter, the ground temperature is below zero, and the temperature of high-altitude clouds is even lower. Water vapor in the cloud condenses directly into small ice crystals and snowflakes. When these snowflakes increase to a certain extent, the airflow can't hold, and falling from the clouds to the ground means snow. If there is a strong updraft, the air temperature will be higher, just like a big hand holding snowflakes. Snowflakes grow up in the clouds for a longer time and fall more.

See the lightning before you hear the thunder

The reason why you see lightning first and then hear thunder is because in the air, light travels fast and can reach the ground soon, while sound travels slowly in the air and will reach the earth in a short time. So you will hear lightning first, and then thunder. In fact, lightning and thunder appear at the same time.

The reason why the time to reach the ground is so different is that the speed of light is 3,000,000 kilometers per second, while sound can only travel 0.34 kilometers in the air for 65,438+0 seconds. The speed of sound is only one-ninth of the speed of light.

Lightning is long and short, loud and quiet. You can roughly judge the height from the clouds to the ground according to the time when the sound reaches the ground. It doesn't take much time for light to reach the ground, which can be considered as 0. How many seconds is the interval between seeing lightning and hearing thunder multiplied by 340 meters, which is the distance from lightning to you.

Lightning will reflect when it meets clouds or tall buildings, so it usually takes some time for lightning to disappear after lightning.