What are the characteristics of frontal precipitation? Why does a front get precipitation?

When a front is active, the precipitation caused by the rising cooling and condensation in the warm and humid air is called frontal rain. Fronts are often accompanied by cyclones, so frontal rain is also called cyclonic rain. There are systematic cloud systems on fronts, but not every type of cloud is.

can produce precipitation.

Frontal rain is mainly produced in Nimbostratus, in which Nimbostratus is the thickest, and it is a mixture of cold and warm air.

The upper part is ice crystals, the lower part is water droplets, and the middle part often coexists with ice and water, which can quickly cause the collision effect, because the thickness of the cloud is large, and the cloud droplets pass a long distance in the process of flushing and merging, which is conducive to the increase of cloud droplets, and the bottom of the Nimbostratus cloud is close to the ground, and the raindrops are not easy to be evaporated in the process of descending, which is very conducive to the formation of precipitation. The thicker the rain layer, the closer the cloud base is to the ground, and the stronger the precipitation.

Altostratus clouds can also produce precipitation, but Cirrostratus clouds generally do not precipitate. Because Cirrostratus clouds are thinner, the cloud base is far from the ground, and the water content is there.

There are few raindrops, and even if there are raindrops falling, it is not easy to reach the ground.

Frontal precipitation. The characteristics are: the horizontal range is large, and a wide range of precipitation areas with band-like distribution are often formed along the front, which is called the precipitation zone.

As the average position of the front shifts seasonally, so does the position of the precipitation band. For example, from winter to summer, the position of the precipitation belt in China gradually shifted northward, in May in South China, and in early June to Nanling.

The first line of Wuyi Mountain, the first line of the Yangtze River in late June, and the Huai River in July.

In August, it will move south to North China, from summer to winter, and in late August, it will begin to withdraw southward from Northeast North China, and in September it will reach the coast of South China, so the southward retreat is much faster than the northward advance.

Another characteristic of frontal precipitation is that it lasts for a long time, because the rise rate of stratiform clouds is small, the water content and precipitation intensity are relatively small, and some pure water clouds rarely experience precipitation, and precipitation occurs also drizzle.

However, frontal precipitation lasts for a long time, ranging from a few days to 10 days and a half a month, and sometimes as long as more than one month"During the Qingming Festival, it rained a lot"It is an accurate and appropriate description of the frontal precipitation phenomenon in the south of the Yangtze River in China.

According to the causes and forms of air upward movement, precipitation is divided into three main types: convective rain, topographic rain, frontal rain, convective rain is the expansion of air by heating, generally in higher temperatures, hotter areas, it is easy to form convective rain, convective rain is the most at low latitudes, the precipitation time is generally in the afternoon, convective rain is thundershowers; Topographic rain is a moist airflow blocked by the mountain and forced to "climb", forming topographic rain on the windward slope, and the topographic rain mostly occurs on the windward slope of the mountain. Frontal rain is the meeting of cold and warm air, warm air is relatively light, and is "lifted" by cold air to form precipitation Precipitation in most parts of eastern China is frontal rain, the first characteristic of frontal precipitation is that the horizontal range is large, often forming a wide range of precipitation areas distributed in a belt along the front, and another characteristic of frontal precipitation is that it lasts for a long time.

Why: Precipitation requires air to rise and cool, and then precipitation is formed. When a warm front encounters colder air during movement, it will actively rise, forming the conditions for precipitation, so there will be precipitation at the moving front.

On the contrary, a cold front tends to move downward when it encounters relatively hot air, and the air behind the front is forced to lift and form precipitation.

The strength of the cold and warm air masses in the cold front and warm front is different, so the type of front and the direction of the forward forward are also different. A cold front is a front in which a cold air mass actively moves towards a warm air mass (Figure a). In the diagram, the cold air mass part is generally drawn with an arrow in the direction of the forward propulsion of the cold air mass, which is in the opposite direction to the arrow of the air flow movement of the warm air mass that is forced to lift on the front.

A warm front is a front in which a warm air mass actively moves towards a cold air mass (Figure B). In the diagram, the direction of the air flow of the warm air mass climbing along the front is the same as the direction of the cold air mass on the other side of the front.

Please take a closer look:Frontal rainWhen a front is active, the precipitation caused by the rising cooling and condensation in the warm and humid air is called frontal rain. Fronts are often accompanied by cyclones, so frontal rain is also called cyclonic rain.

There are systematic cloud systems on fronts, but not every oneYunducan produce precipitation.

It refers to the meeting of the cold air mass and the warm air mass, and the warm air mass is lifted to form rainfall, such as the plum rain in the south and the cold wave in the north. Convective rain refers to the heat of a place and the heat of the air to rise, forming rainfall, such as heavy rains in summer.

Frontal rain features.

1. When the front is active, the precipitation phenomenon caused by the rising cooling and condensation in the warm and humid air is called frontal rain.

2. The front is often accompanied by a cyclone, so the rain on the front side is called a cyclonic rain. There are systematic cloud systems on fronts, but not every type of cloud produces precipitation. When two air currents with different properties meet, the interface between them is called a front.

3. On the front, warm, wet, and lighter air is lifted over cold, dry, and heavier air. In the process of uplifting, the water vapor in the air cools and condenses, and the precipitation formed is called frontal rain.

The precipitation process that occurs before the temperature change is the "warm peak" frontal system.

Cold front: When transiting, there are often strong winds, cloudy days, precipitation, and cooling weather; After the transit, the temperature and humidity decreased, the air pressure increased, and the weather became clearer.

Warm front: When transiting, there are often cloudy days, rainy weather and other weather; After the crossing, the temperature rises, the air pressure drops, and the weather becomes clearer.

According to the thermodynamic classification method, if the cold air mass actively pushes the warm air mass, it is called a cold front. Otherwise, it is called a warm front. If the cold and warm air masses are equal, it is called a quasi-quasi-stationary front. If a cold front catches up with a warm front, a prison front will form.

Cold front: During the movement of the front, the cold air mass plays a dominant role, pushing the front to move towards the side of the warm air mass, this kind of front is called a cold front. After the cold front crossed, the cold air mass occupied the position where the warm air mass was originally located.

Cold fronts occur throughout the year in China, especially during the winter months. In the process of cold air movement, due to the different degrees of degeneration, or a small stream of cold air supplements the southward, and a secondary front can be formed after the main front, that is, in the same air mass. Generally speaking, the temperature difference between the two sides of the main front is larger, while the temperature difference between the two sides of the secondary front is smaller.

After the cold front passes, the temperature drops, the air pressure rises, and the weather turns sunny and good.

Warm front: In the process of moving the front, if the warm air plays a dominant role and pushes the front to move towards the side of the cold air mass, this kind of front is called a warm front. After the warm front crosses, the warm air mass occupies the position of the original cold air mass.

Warm fronts are mostly associated with cold fronts in Northeast China and the middle and lower reaches of the Yangtze River. After the passage of the warm front, the temperature rises, the air pressure drops, and the weather turns cloudy and rainy.

Quasi-stationary front: When the forces of cold and warm air masses are equal and the front moves very slowly, it is called a quasi-stationary front. In fact, there is no such thing as absolute stillness.

During this period, the cold and warm air masses are also fighting each other, sometimes the cold air masses are dominant, and sometimes the warm air masses are dominant, causing the front to swing back and forth.

Prison Front: Two fronts formed by warm, colder and colder air masses (three air masses with different properties) when they meet, and then one of the fronts catches up with the other.

Since the front is the junction area of cold and warm air masses, the air activity is very active, and a series of clouds, rain, wind, precipitation and other weather can be formed. In China, there are frontal activities throughout the year, with cold fronts being the most frequent and can occur in large areas of the country. At the turn of spring and summer, there is often quasi-stationary front activity.

The activities of the front often go through the process of generation, strengthening, and dissipation. It generally lasts about 3-5 days.

Hello lz......

The slope of the front is directly proportional to the difference in wind speed, but inversely proportional to the difference in temperature. The effect of the two on the climb and lift of the warm air mass is reversed, which means that it is not the fast movement of cold air (or the fast movement of warm air in the warm front) that causes more rain on the front. [To put it simply, in the presence of a certain amount of warm air, the stronger the cold air, the smaller the slope, the more the cold air tends to wedge into the warm air, and the cold front advances faster, and vice versa.]

The fundamental reason for the small slope of the front and the high precipitation is that in the presence of a certain amount of warm air, the larger the slope, the smaller the rising area, and the more concentrated the rainfall. When the slope is small, the rising area is "spread out", and the rainfall is weaker.

Therefore, in the rainy season in South China, the slopes of the stationary front, quasi-stationary front, and even the A angle are close to vertical. Such frontal rainfall is the heaviest, far exceeding that of warm and cold fronts.

The amount of precipitation on the front is related to the amount of water vapor in the warm air on the front. Whether it is a cold front or a warm front, if there is less moisture in the warm air, there will be less precipitation on the front.

Under the premise that there is a lot of water vapor in the warm air, if the slope of the front is relatively large, it means that the cold air moves fast, and the warm air in front of the front is forced to rise rapidly in a short time, and a large amount of water vapor condenses, forming more precipitation. For example, the formation of summer rainstorms and winter blizzards in northern China.

Because of the large slope, the air convection memory, if the air contains more moisture, it will condense when it encounters cold air, so the slope is large, and the rainfall will be more.

Because the steep peak surface is more likely to form water vapor accumulation, there is a lot of precipitation.

Due to the great difference in the nature of the air masses on both sides of the front, the air movement near the front is active, and there is a strong upward and downward movement in the front, and the airflow is extremely unstable, often causing drastic weather changes. However, it is not necessary to say that there must be precipitation on the front, and the sandstorm is not brought by the cold front.

As for the angle of the front, you can draw a triangle, which is a projection of the front, and obviously, the angle of the front is small, and the range of control is large

If there is anything wrong, please bear with me

In meteorology, the cold air with high pressure is called a high-pressure ridge, which is like a wedge, and the low-pressure air with moisture is called a low-pressure trough, and the contact part will cause rainfall. As a meteorological phenomenon, it is not a geometric shape that can be observed with the eye, and it is not a concept of the size of a front that is difficult for such professionals to understand.

In meteorology, the air is called a cold high pressure wedge ridge with high pressure to low pressure moisture like it is called a low pressure trough and will have rain in contact. As a meteorological phenomenon in the eyes of professionals such as geometric shapes are not observed, it is difficult to understand the concept of the size of the front.

Answer B: This question examines common weather systems. The frontal precipitation is located on the side of the cold slag air mass, so the precipitation of the warm and chauffeur is in front of the front, and the precipitation of the cold front is behind the front.