What is the relationship between cyclones and anticyclones and cold fronts and warm fronts?

Cyclone

Cyclone

In the northern (southern) hemisphere, the horizontal airflow in the atmosphere is a large vortex that rotates counterclockwise. At the same height, the air pressure at the center of a cyclone is lower than that around it, also known as low pressure. Cyclones are approximately circular or elliptical in shape and vary widely in size. The horizontal scale of small cyclones is several hundred kilometers, and the large ones can reach three or four thousand kilometers. In cyclones, the weather often changes dramatically, and it is the weather system that people are most concerned about and the first to study. Usually classified according to the main areas or thermal structures of cyclone formation and activity. According to the region, it can be divided into extratropical cyclones, tropical cyclones and polar cyclonic vortices; according to the thermal structure, it can be divided into cold cyclones and thermal low pressure.

There are vortex motions in the atmosphere similar to those in rivers. There are two types of rotational motions, clockwise and counterclockwise: cyclones and anticyclones, which are both large-scale horizontal vortex motions in the atmosphere. In a cyclone, in the Northern Hemisphere, the air moves in a counterclockwise direction, with the lowest pressure in the center, gradually increasing outward. The air continues to flow into the center, forming an updraft, also known as low pressure. Its diameter: the small one is tens of kilometers, and the large one is thousands of kilometers. Rainy weather and strong winds often occur when cyclones are affected.

There are various large and small vortices in the atmosphere. Some of them rotate counterclockwise and some rotate clockwise. Among them, the large horizontal vortices are called cyclones and anticyclones respectively. , that is, low pressure and high pressure.

Related terms

Cyclone: ??Cyclone and low pressure. A large vortex that occupies three-dimensional space and has closed isobaric (altitude) lines at the same height (isobaric surface), and the central air pressure (height) is lower than the surrounding one. In the Northern Hemisphere, the air rotates counterclockwise; in the Southern Hemisphere, the direction of rotation is opposite.

Anticyclone: ??Anticyclone is also called high pressure. Cyclones and anticyclones are two aspects of one system.

Jianghuai cyclone: ??refers to the cyclone that appears in the Jianghuai region.

Northeast cyclone: ??also known as Northeast low pressure. A cyclone active in Northeastern my country. It is one of the important weather systems affecting our country.

Frontal cyclone: ??also known as polar frontal cyclone, wave cyclone, and baroclinic cyclone. A strong baroclinic cyclone arises from the fluctuations in the development of the extratropical polar front. In my country, some fronts develop into frontal cyclones after entering a low pressure trough, shallow low pressure or typhoon.

Cold vortex: short for cold low vortex. The center of the vortex is cooler than the surrounding vortex, and its intensity increases with height.

Northeast Cold Vortex: A high-altitude large-scale cold vortex active in or near Northeastern my country. It is a deep system capable of lasting 3-4 days or more.

Southwest vortex: also referred to as southwest vortex. A shallow low vortex is generated at low altitude in southwest my country under the combined action of the special terrain and certain circulation of the Tibetan Plateau and southwest China.

Anticyclone

An anticyclone refers to a horizontal air vortex in which the central air pressure is higher than the surrounding air pressure. It is also the high pressure in the air pressure system. In the Northern Hemisphere anticyclone, the low-level horizontal airflow diverges outward in a clockwise direction, while in the Southern Hemisphere anticyclone, the low-level horizontal airflow diverges outward in a counterclockwise direction. The horizontal scale of anticyclones is larger than that of cyclones. For example, the Mongolia-Siberia High in winter occupies 1/4 of the Asian continent. The central air pressure value of an anticyclone is generally around 1020-1030hPa, and can reach as high as 1078hPa. The wind speed of an anticyclone is small, the maximum wind speed on the ground is only 20-30m/s, and the wind in the central area is weak.

An anticyclone has the highest pressure in its center and gradually decreases outward, also known as high pressure. In the Northern Hemisphere, air in an anticyclonic region flows clockwise. Its diameter is as small as a few hundred kilometers and as large as five or six thousand kilometers, such as the anticyclone on the Asian continent in winter and the subtropical high pressure over the Pacific in summer. Downdrafts form as the air in the anticyclone radiates to all directions. Therefore, when an anticyclone controls the city, the weather is generally better. Winter is sunny and cold, summer is sunny and hot, and spring and autumn are windy, sunny, and crisp.

(1) Types of anticyclones

Anticyclones are divided into extratropical anticyclones, subtropical anticyclones and polar anticyclones according to the geographical location where they are generated. According to the structure of anticyclones, they are divided into cold anticyclones (cold high pressure) and warm anticyclones (warm high pressure). Cold high pressures (such as the Siberian high pressure) usually reduce to very weak intensity at a height of 3 to 4 km, while warm high pressures (such as the subtropical high pressure) are deep systems that can extend to the tropopause.

(2) Extratropical cold anticyclone (cold high pressure) and cold wave

In the winter half of the year, the continental surface undergoes strong radiation cooling, and air accumulates on the continent to form cold high pressure. The Mongolia-Siberia High in East Asia is the most powerful cold high in the world. Its eastward movement is characterized by causing large-scale cold air activities, resulting in strong winds and cooling weather in the areas it passes through. Where the front edge of cold air meets warm air, clouds and rain are formed, and the main body of cold high pressure reaches the area to maintain sunny weather.

The Central Meteorological Administration has stipulated that during cold high pressure activities, cold air invades, causing the temperature to drop by more than 10°C in 24 hours, with the lowest temperature below 5°C, accompanied by a northerly storm of about level 6 Wind, as a criterion for issuing a cold wave warning. There are an average of 3 to 4 nationwide cold waves in China every year during the winter half. March to April every year is the season with the most frequent cold wave activities, followed by November.

A nationwide cold wave usually begins in late September and does not end until May of the following year. Each cold wave takes about 3 to 4 days from its onset to its end (moving out of China).

It is impossible for cold air activity in summer to reach cold wave standards, but a 24-hour temperature drop of 10°C is still possible. In summer, cold air moves toward the southeast, which forces warm air masses to rise, causing water vapor to rise and condense into clouds and cause rain. It is an important cause of precipitation in eastern China.

(3) Subtropical anticyclone (subtropical high pressure) and Meiyu

The subtropical high pressure zone is located in the latitude range of 25° to 35° in the northern and southern hemispheres. Due to differences in sea and land distribution and topography, the subtropical high pressure breaks into several closed centers, namely the subtropical high pressure. The subtropical high pressure belt in the Northern Hemisphere splits into: Eastern Pacific High, Western Pacific High, North African High and North Atlantic High in the summer half. In the winter half of the year, there are: North Pacific high pressure, North Atlantic high pressure and North African high pressure. The subtropical high pressure is strong in summer and weak in winter, and weak in summer and winter.

The subtropical high pressure is a stable, less dynamic, extremely deep warm high pressure with a wide range of downdrafts. Under its control, the weather is clear. Eastern China is located on the west side of the North Pacific subtropical high. In summer, it gradually expands westward and northward, transporting water vapor to eastern China with southeasterly winds. It is one of the important sources of water vapor for precipitation in eastern China. Heavy rains in the Yangtze-Huaihe River Basin in summer are closely related to it. In midsummer, if the subtropical high-pressure ridge extends to the Jianghuai region, the downdraft on the ridge makes it difficult for water vapor to condense into clouds. Instead, there will be hot and rainless drought weather. In winter, the North Pacific subtropical high shrinks and weakens toward Hawaii, which has little impact on China's weather and climate. Phenomenons similar to those in eastern China can also occur in the eastern United States and the east coast of other continental subtropical latitudes.

In areas on the continent that are controlled by subtropical high pressure all year round, the climate is abnormally dry, forming world-famous deserts, such as the African Sahara Desert.

(4) Distribution of anticyclones

The paths of anticyclones are not as clear as those of cyclones. As the air sinks at 25° to 30° south and north latitudes, it spreads near the surface to form anticyclones. Therefore, subtropical anticyclones exist in the ocean throughout the year. On the continent, subtropical anticyclones tend to develop well in the winter months; in summer, due to high temperatures, various types of monsoons form and anticyclone belts break up.

Leng Feng

What is Leng Feng?

Cold front is the most common type of front in my country, and it can move across the country. However, due to the different configurations and moving speeds of the cold front and the upper-altitude trough, the distribution of clouds and precipitation near the cold front is also significantly different. Some mainly appear behind the front; others mainly appear in front of the front.

According to the analysis of meteorologists, the weather conditions of cold fronts can be roughly divided into two types:

The first type: the cold front moves slowly, has a small slope, and is in the 700hpa trough in the air Front, often called a Type 1 cold front. For this type of cold front, because the cold air mass moves forward on the one hand, the warm air mass in front of the front moves forward on the other hand, and is forced to slide upward along the front. When the water vapor conditions are sufficient, cloud systems and clouds are generated on the front. precipitation.

Because this type of cold front is in front of a high-altitude trough, which is conducive to the upward movement of the air. Before the front arrives, the warm air mass is not cloudless. With the arrival of the cold front, there are often cirrus clouds in the air first. Stratus clouds, the clouds gradually thicken as the front approaches, and when the front passes, they become nimbostratus clouds. The width of the rain area is about 150 to 200 kilometers.

The second type: the cold front moves faster, has a larger slope, and is located behind or near the 700hpa trough in the high altitude. It is often called the second type of cold front. The cold advection above this type of cold front is strong, the airflow sinks, and only the warm air near the ground front is lifted. However, the front slope is large, and there is a strong upward movement of airflow. There are obvious differences in weather conditions between winter and summer. The warm air mass in summer is relatively humid and inherently unstable. Coupled with the strong cold advection above, it becomes even more unstable. Therefore, strong cumulonimbus clouds often form near the front, which are arranged near the front like a cloud embankment. When the cold front comes, thunderstorms and bursts of precipitation occur, but the rainfall area is only tens of kilometers away. In winter, the warm air in front of the front is located in front of the trough, and the airflow rises to form cirrus clouds, cirrostratus clouds, altostratus clouds, and nimbostratus clouds. There is a wide continuous precipitation area near the ground front. After the precipitation stops, strong winds often appear. People also call this kind of front a dry cold front.

Because cold fronts move faster or slower, when the cold front moves slowly, the warm air rises more slowly and steadily, so stratiform clouds are more likely to appear, and rainfall is also gentler; when the cold front moves slowly, When the weather is relatively fast, warm air will be quickly lifted up by cold air, so thick cumulonimbus clouds are often easily formed, and at the same time, there will be heavy wind and rain with thunder and lightning.

Occurrence time: Cold front activity occurs all year round in the northwest region. It is strong in winter and weak in summer, but the frequency of occurrence is similar. Its shape and movement speed are greatly affected by terrain.

General characteristics of cold front activities: Cold front activities occur in East Asia. The frequency of cold front activity is more in the north than in the south, and the frequency of cold fronts in the southwest is the least; it is more frequent in the winter half of the year than in the summer half of the year, most in spring and least in autumn.

Where it occurs: The intensity of cold fronts is strongest in winter, and can often drive directly into South China and the South China Sea, causing cold wave weather. In summer, cold fronts are weak and mainly active in the north. Cold fronts in summer often bring thunderstorms.

North China is the only place where cold front activities in China must pass. In the Northeast, there are cold front activities all year round, especially in spring and autumn, where cold front activities are frequent.

There are three sources of cold fronts in these two areas: west, northwest, and north-northeast. In winter, cold fronts mainly cause cooling and strong winds, and they can also produce thunderstorms in summer. In spring, cold fronts often cause strong winds and precipitation in the Northeast, while in North China they often only cause sandstorms.

After the cold front:

1 Temperature: drop

2 Air pressure first drops and then rises

3 Precipitation: It will rain after the front

When a front moves, if the warm air mass plays a leading role and pushes the front to move to the cold air side, this kind of front is called a warm front. In my country, warm fronts often appear on the east side of the cyclone center, and often appear in pairs with cold fronts. When a warm front passes, it is usually accompanied by rain, the air pressure also decreases, and the temperature will increase.

Warm front

Warm front

When the front moves, if the warm air plays a leading role and pushes the front to move to the side of the cold air mass, this kind of front movement Called a warm front. After the warm front passes, the warm air mass takes over the original position of the cold air mass. Warm fronts are mostly active in Northeast China and the middle and lower reaches of the Yangtze River, and are mostly associated with cold fronts. After the warm front passes through, the temperature rises, the air pressure drops, and the weather becomes cloudy and rainy. Opposite the cold front.

Warm front weather model

In the cold air mass under the warm front, because the air is relatively humid, stratocumulus and cumulus clouds are often produced under the action of airflow convergence and turbulence. . If the raindrops falling from the warm air above the front evaporate in the cold air mass, the water vapor content in the cold air mass increases, and when it reaches saturation, cumulus and stratus clouds will form. If this saturated condensation phenomenon occurs in the ground layer near the front, frontal fog will form. The above is the general situation of warm front weather, but when the warm air is unstable in summer, cumulonimbus clouds, thunderstorms and other intermittent precipitation may also occur. In spring, when there is very little water vapor in the warm air mass, there are only some high clouds and little precipitation.

Obvious warm fronts appear less frequently in my country, and are mostly accompanied by cyclones. It generally appears in the Yangtze-Huaihe River Basin and Northeast China in spring and autumn, and in the Yellow River Basin in summer.

Low pressure forms a cold and warm front, and the weather is fine under the control of high pressure. It cannot be said that there is a relationship between them, nor can it be said that there is no relationship at all! Because there are integrity and differences between geographical environments.