How does water interact with the atmosphere?

Interaction between hydrosphere and atmosphere

Section 1 Water Vapor and Weather

The water and atmosphere on the earth are the most basic substances for all biological activities (including human survival), so the hydrosphere and atmosphere have become the two most direct spheres that affect human survival. These two circles play the most important role in the natural geographical system. They are not only in constant motion, but also penetrate, restrict and interact with each other.

Water vapor is the link between the atmosphere and hydrosphere. It is not only a part of the hydrosphere, but also an important part of the atmosphere. The distribution of water vapor content in the atmosphere and its three-phase changes have caused the occurrence of weather phenomena in the atmosphere and the regional differences in the distribution of these weather phenomena. In the final analysis, all weather phenomena in the atmosphere are the result of water vapor. It can be said that without the participation of water vapor, there would be no weather phenomenon.

I. Water vapor distribution and weather

The water vapor in the atmosphere mainly comes from the evaporation of liquid water in the hydrosphere (surface), which is controlled by temperature and water source and distributed unevenly in the atmosphere. The higher the temperature, the richer the water source and the more water vapor content in the atmosphere. On the contrary, the less. There is a lot of water vapor in the atmosphere of ocean and wet land surface, but there is little water vapor over dry land surface; Water vapor content is high in low latitudes (except tropical desert areas) and low in high latitudes. The more water vapor content and humidity in the atmosphere, the easier it is to form precipitation. Therefore, areas with abundant water vapor in the atmosphere often form a humid climate, whereas areas with less water vapor often form a dry climate; The more water vapor, the better the weather phenomenon. Therefore, the air humidity over the ocean is high, and the maritime climate zone affected by the ocean often forms cloudy, foggy and rainy weather. However, the dry continent is dominated by partly cloudy and sunny weather. Even if fog is formed, it is mainly radiation fog near the ground, which dissipates quickly and has less annual precipitation. Due to the high temperature in low latitudes, it is beneficial to evaporation. However, the vast ocean waters are rich in water and water vapor in the atmosphere, and rainy weather often occurs. The annual precipitation is very abundant, while in high latitudes, it is the opposite. Even if there is precipitation, the precipitation is very small, mostly snowfall.

In the vertical direction, the water vapor content near the ground is the highest, and the higher the altitude, the less the water vapor. Near the tropopause (10Km), the water vapor content in the atmosphere is almost zero, and the atmosphere above the stratosphere basically contains no water vapor. So almost all weather phenomena in the atmosphere are concentrated in the troposphere, and there are almost no weather phenomena in the stratosphere and above.

Second, water vapor phase transition and weather

All weather phenomena are actually the result of water vapor movement and its phase change in the atmosphere. With the fluctuation or horizontal movement of airflow, the water vapor in the atmosphere will change from gaseous state to liquid state and solid state due to the change of temperature (mainly referring to the decrease of temperature), that is, the water vapor will condense and bloom, thus producing various weather phenomena. The main weather phenomena are: clouds, rain, snow, fog, dew, frost, hail, graupel and so on.

(1) clouds and fog

Cloud is the condensate formed by water vapor in the air, which is mainly composed of water droplets, supercooled water droplets and ice crystals. From the material composition, it can be divided into three categories: water cloud, ice cloud and mixed cloud. Cloud is the foundation of precipitation and the middle link of the earth's water cycle. A certain cloud shape is often accompanied by a certain weather, so clouds have a certain indication of weather changes. Fog is water droplets and ice crystals suspended in the air near the ground. When the air is full of water vapor and saturated, the water vapor condenses to form clouds. The richer and wider the water vapor is, the thicker the cloud is.

The formation of clouds greatly reduces the transparency of the atmosphere and weakens the solar radiation reaching the surface, so that the temperature will not rise too high during the day, for example, the temperature is often low on cloudy days; At the same time, the atmospheric inverse radiation is enhanced, which has a certain heat preservation effect on the ground, especially at night, and it is often warmer on cloudy days. The influence of clouds on the surface temperature is shown in figure 10- 1. In a word, the formation of clouds changes the surface temperature and reduces the daily temperature difference, so that the temperature will not rise too high during the day and fall too low at night.

Figure 10- 1 schematic diagram of cloud influence on surface temperature.

(2) Rain and snow (precipitation)

Rain refers to liquid water droplets falling from the cloud to the surface, and snow refers to solid ice crystals falling from the cloud. Different clouds have different horizontal range, cloud height, cloud thickness, cloud water content, cloud temperature and ascending and descending airflow, so the form, intensity and nature of precipitation are obviously different. Among them, the amount of precipitation is directly related to the content of water vapor in the atmosphere. On the world precipitation distribution map, the general trend of precipitation distribution is that the ocean is higher than the land, and the low latitude is higher than the high latitude; The form of precipitation is related to temperature, with liquid rainfall at low latitudes and solid snowfall at high latitudes.