Why is the weather always changeable?

Weather is the general name of atmospheric conditions (such as cold and warm, wind and rain, dry and wet, sunny and so on). ) 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. All kinds of weather systems have certain time and space scales, and they are intertwined and influence each other. The combination of many weather systems constitutes a large-scale weather situation and hemispheric and even global atmospheric circulation.

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. It is a necessary condition for the emergence and development of convective weather system that the equatorial and low latitudes are hot and humid all the year round and the atmosphere is unstable. Mid-high latitudes are areas where cold and warm air currents often cross. 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, understanding the formation, structure, movement and change of weather system and its relationship with geographical environment is of great significance for understanding the formation, characteristics and change of weather and climate and predicting the evolution of geographical environment.

References:

Meteorology and Climatology in Zhou Shuzhen (Third Edition)

Answer 2

Weather is the change of atmospheric physical conditions in a short time, and the main factors affecting weather are air mass and front.

1) air mass: it can be divided into warm air mass and cold air mass. When controlled by a single air mass, the weather is monotonous and often sunny. When the air mass in a place is replaced by a new air mass, the weather will change.

2) Front: the interface between cold and warm air masses. When the cold air mass moves to the warm side, it is a cold front; On the contrary, when the warm air mass moves to the cold side, it is a warm front. Frontal transit areas are often accompanied by temperature changes, rain and snow, strong winds or sandstorms.

3) Cyclone and anticyclone: Cyclone is accompanied by low pressure, showing rainy weather; The anticyclone is accompanied by high air pressure, indicating that the weather is fine. The position of a place in cyclone and anticyclone determines the wind direction of this place.