What are the causes of cold and warm cyclones?

I. Front Type and Weather Control According to the moving direction of cold and warm air masses on both sides of the front, the front can be divided into cold front, warm front and quasi-static front. According to the moving speed of cold air mass, cold front can be divided into fast cold front and slow cold front. Four types of fronts, except the fast-moving cold front will bring storms, other fronts will bring continuous precipitation when crossing the border. When the cold and warm air masses are evenly matched, or encounter terrain obstacles, the front moves slowly, or swings in an area for a long time, resulting in rainy weather. This kind of front with small moving amplitude is called quasi-static front. Examples: ① Early summer (June), rainy weather from the middle and lower reaches of the Yangtze River to southern Japan; (2) In the winter half year, the southward cold air was blocked by Yunnan-Guizhou Plateau, and the cold front came to a quasi-static stop between Kunming and Guiyang, forming a quasi-static stop front in Kunming. Second, the interpretation method of cold and warm front 1 According to the definition of cold and warm front, judge who is the most powerful and who is the main force of cold and warm air movement. The warm front is that the warm air mass climbs actively, and the cold front is that the cold air mass cuts into the lower part of the warm air mass actively. 2. Judging from the moving direction of the front: as shown on the right, if the front moves from A to B, it means that the warm air mass has defeated the cold air mass, and the front is a warm front; If the front moves from B to A, it means that the cold air mass has defeated the warm air mass, and the front is a cold front. 3. From the moving direction of the cold air mass, as shown in the figure, the warm air mass climbs upward, but the moving form of the cold air mass is different. The cold air mass at the warm front is forced to turn around, and the cold air mass at the cold front does not turn around. 4. Judging from the steepness of the front, the angle between the cold front and the ground is greater than that between the warm front and the ground. 5. From the position of rainfall relative to the front, as shown in the above figure, rainfall mainly occurs on the side where the included angle between the front and the ground is small, or on the side of the cold air mass. Whether precipitation is before or after the front is judged according to the moving direction of the front. For example, the cold front map shows that the cold air mass is stronger than the warm air mass, and the cold front will move eastward. Compared with the moving direction of the front, the precipitation is behind the front, and sometimes there is a little precipitation before the cold front, which may be because of the wind (sweeping rain); Similarly, warm front precipitation only appears in front of the front. 6. Judging from the symbols of cold and warm fronts, cold and warm fronts has fixed symbols, with a sharp triangle for the cold front and a semicircle for the warm front. From which side does the symbol protrude, that is, which direction does the front face face. 7. According to the weather characteristics when the front is controlled, it is judged that there will be rain and snow, cooling and pressurization when the cold front passes through, and there will be rain, heating and depressurization when the warm front passes through, or the specific type of the front can be judged according to the temperature and pressure changes before and after the front passes through. Third, the description of the weather changes before and after the ferry. The examination of front in college entrance examination is mainly reflected in the description of weather characteristics or the judgment of front type according to weather characteristics. Although this kind of questions is not difficult, the students' actual answers show a lack of rigor and hierarchy. For example, on the right, there is a schematic diagram of the temperature and pressure changes in Shanghai. Please describe the weather before and after the transit of this weather system. (1 1) Answer: The weather system is a cold front (2). ① Before crossing the border: sunny weather, high temperature and low air pressure (3 points); (2) When crossing the border: in rainy and snowy weather, the temperature drops and the air pressure rises (3 points); ③ After crossing the border, the weather turns fine, the temperature is low and the air pressure is high (3 points). Questions to pay attention to when answering this question: 1. Make clear what the weather system is and express it in your answer. Although the title does not directly ask what the weather system is, it is the key to solving the problem. Once the judgment is wrong, the whole game will be lost. As can be seen from the answer, this question has a clear scoring point, that is to say, the score, which examines the students' answering habits. This kind of problem is called the hidden problem in the problem. Get attention! 2. There are three levels to describe the weather change process: before, during and after the transit. The position cannot be reversed when expressing, and it is progressive in time. In concrete expression, it generally includes three aspects, namely, sunny weather, high and low air pressure and high and low temperature. The relationship between temperature and air pressure here is caused by heat, so the temperature and air pressure are inversely proportional. Moreover, the temperature and pressure before and after the transit show state values, that is, higher temperature, lower pressure, lower temperature and higher pressure. When crossing the border, it shows variability, such as "when crossing the border, the temperature drops and the air pressure rises". As for whether the weather is cloudy or sunny, there will be rain and snow only when crossing the border, and it will be sunny whether it is controlled by cold air mass or warm air mass before and after crossing the border. Summary: This is a common examination method. Although the topic is not difficult, it is easy to lose points when doing it. Pay attention to the examination of students' thinking and the cultivation of answering habits. As long as you master the general idea of answering questions and pay attention to the hierarchical and progressive expression, you can do this kind of topic well. 4. Frontal cyclone Frontal cyclone is the product of the combination of frontal and cyclone. As long as there is a cyclone, it is necessary to associate the front with it. As shown below: Take two points on the trough line and ridge line respectively, and draw the wind direction to know that cold and warm air masses meet near the trough line and form a front. The airflow diverges near the ridge line, and the cold and warm air masses will not meet to form a front. Near the trough line, cold air from the north pushes warm air from the south, forming a cold front. 1. The position where the front is generated is in the trough of low pressure (gas convergence). The main cyclone on the front is cyclone, and the front rotates with the cyclone. 2. Method of judging cold and warm front in frontal cyclone: The cyclone in the northern hemisphere rotates counterclockwise and points to the center of low pressure, so when the airflow passes through slot line A, it is natural that the cold air in the north pushes the warm air in the south to form a cold front; When the airflow passes through slot line B, it is naturally the warm air in the south that pushes the cold air in the north to form a warm front. Similarly, a cold front is formed at C and a warm front is formed at D in the southern hemisphere, as shown above. 3. Distribution law of precipitation area in frontal cyclone: precipitation is distributed on one side of cold air mass, and the inward direction of cyclone rotation is the direction of cold and warm front, so the cold front forms a narrow cold front cloud system behind the front, and the warm front forms a wide warm front cloud system before the front. There was also a small amount of precipitation before the cold front, which may be due to the wind. Interpretation method of frontal cyclone: 1. First, it is necessary to judge whether there is a frontal cyclone. According to whether there is a front or not and whether there is a low-pressure center, the questioner's intention is clear, and the image information and text information are completely interpreted. 2. Determine the hemisphere where the frontal cyclone is located. According to the direction of the wind direction relative to the horizontal pressure gradient force, see if it is left or right. 3. Judging the front type near the trough line: According to the strength of cold and warm air flow, draw the clockwise direction of hemisphere cyclone rotation. If the cold air mass beats the warm air mass to form a cold front, if the warm air mass beats the cold air mass to form a warm front. 4. Determination of front precipitation position: Determine the moving direction of front according to the rotating direction of cyclone, and determine the front and back according to the moving direction of front, with cold front precipitation behind the front and warm front precipitation before the front. 5. Determination of the wind direction at any point: In the isobar diagram, the wind direction at any point is determined by the sketch method. Firstly, the direction of horizontal pressure gradient force is determined, and then the wind direction is determined according to the influence of geostrophic deviation, that is, the northern hemisphere is right-biased and the southern hemisphere is left-biased.

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