Why does the weather change?

Weather is the general name of atmospheric conditions (such as cold and warm, wind and rain, dry and wet, sunny and sunny, etc.). ) and its changes in a short time in a certain area. Weather system usually refers to the atmospheric motion system with typical characteristics, such as high pressure, low pressure, high pressure ridge and low pressure trough, which cause the change and distribution of weather. Various weather systems have certain spatial and temporal scales, and they are intertwined and influence each other. Many weather systems are combined to form a large-scale weather situation and a hemisphere.

The weather system is always in the process of rebirth, development and extinction, and there are corresponding weather phenomena in different development stages. Therefore, the weather and weather changes in a region are related to the weather system and its development stage, and are the comprehensive results of atmospheric dynamic and thermal processes.

All kinds of weather systems are formed, developed and evolved in a certain atmospheric circulation and geographical environment, and all reflect the environmental characteristics of a certain region. For example, the polar regions and their 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 polar low-altitude cold high pressure and high-altitude polar vortex and low trough. The equator and low latitudes are hot and humid all the year round, and the atmosphere is unstable. It is a necessary condition for the emergence and development of convective weather system. Cold and warm air currents often cross in the middle and high latitudes. Cold and warm air masses not only come and go frequently, but also have unstable baroclinic, which is an important basis for the formation and development of frontal and cyclone systems. The formation and activities of weather system will in turn have a profound impact on the structure and evolution of geographical environment. Therefore, we must understand and master the formation, structure, movement and change of weather system and its relationship with geographical environment.