Weather changes are the result of weather systems, right?

Weather changes around the world are the result of weather systems. The picture below shows the weather situation in my country at a certain time.

(1) Estimate the number of cold air intrusions in the area shown in the picture.

(2) Draw a schematic diagram of the front profile along line L.

(3) Analyze the impact of weather changes in Beijing on air quality in the next few days. The constantly changing atmospheric state is not only the atmospheric state within a certain time and space, but also the continuous change of the atmospheric state within a certain time interval. Therefore, it can be understood as a collective name for weather phenomena and weather processes. Weather phenomena refer to various natural phenomena that occur in the atmosphere, that is, the comprehensive expression of the spatial distribution of various meteorological elements (such as wind, clouds, fog, rain, snow, frost, thunder, hail, etc.) in the atmosphere at a certain instant. Weather process is the process of changes of weather phenomena in a certain area over time. Weather is a general term for the atmospheric state (such as cold and warm, wind and rain, dryness and humidity, cloudy and sunny, etc.) and its changes in a certain area within a short period of time. Weather systems usually refer to atmospheric motion systems with typical characteristics such as high pressure, low pressure, high pressure ridges, and low pressure troughs that cause weather changes and distribution. Various weather systems have certain spatial and temporal scales, and systems of various scales are intertwined and interact with each other. The combination of many weather systems forms a large-scale weather situation and constitutes hemispheric or even global atmospheric circulation. Weather systems are always in the process of being reborn, developing and dying, and there are corresponding distributions of weather phenomena at different stages of development. Therefore, the weather and weather changes in a region are related to the weather system and its development stage, and are the comprehensive result of the dynamic and thermal processes of the atmosphere. Various weather systems are formed, developed and evolved in certain atmospheric circulation and geographical environments, and they all reflect the environmental characteristics of a certain region. For example, the polar region and its surroundings are covered with ice and snow all year round, and the air is cold and dry. This unique geographical environment has become the background condition for the formation and development of low-altitude cold high pressure in the polar region and high-altitude polar vortices and low troughs. The equatorial and low latitude areas are hot and humid all year round, and the atmosphere is in an unstable state, which is a necessary condition for the occurrence and development of convective weather systems. Mid-to-high latitudes are areas where cold and warm air currents often intersect. Not only do cold and warm air masses alternate frequently, but their baroclinic instability is also an important basis for the formation and development of fronts and cyclone systems. The formation and activities of weather systems will, in turn, have a profound impact on the structure and evolution of the geographical environment. Therefore, it is very important to understand and master the formation, structure, movement and change rules of the weather system and the relationship with the geographical environment to understand the formation, characteristics and changes of weather and climate and to predict the evolution of the geographical environment.