The main source of water vapor in the atmosphere?

Interaction between the hydrosphere and the atmosphere

Section 1 Water Vapor and Weather

The water and atmosphere on the earth are responsible for all biological life activities (including human survival) The most basic substances, therefore, the hydrosphere and the atmosphere have become the two spheres that most directly affect human survival. These two circles play the most important role in the physical geographical system. Not only are they each in constant motion, but they are also interpenetrating, restricting, and interacting with each other.

Water vapor is the link between the atmosphere and the hydrosphere. It is both a part of the hydrosphere and an important component of the atmosphere. The distribution of water vapor content in the atmosphere and its three-phase changes cause the occurrence of weather phenomena in the atmosphere and the regional differences in the distribution of these weather phenomena. The occurrence of all weather phenomena in the atmosphere is ultimately the result of the participation of water vapor. It can be said that without the participation of water vapor, there would be no weather phenomena.

1. Water vapor distribution and weather

Water vapor in the atmosphere mainly comes from the evaporation of liquid water in the hydrosphere (surface). It is affected by temperature and water sources and is unevenly distributed in the atmosphere. . In areas with higher temperatures and more abundant water sources, the content of water vapor in the atmosphere is more; conversely, the water vapor content is less. Oceans and humid land surfaces have a lot of water vapor in the atmosphere, but over dry land surfaces, there is very little water vapor. Low latitudes (except tropical desert areas) have a lot of water vapor, but high latitudes have less. The more water vapor content in the atmosphere and the greater the humidity, the easier it is to form precipitation. Therefore, areas with rich water vapor content in the atmosphere throughout the year are more likely to have a humid climate. On the contrary, areas with less water vapor are more likely to have a dry climate. The more water vapor, the more favorable it is. Weather phenomena occur. Therefore, the air humidity over the ocean is high, and cloudy, foggy, and rainy weather often occurs in marine climate zones affected by the ocean. However, the interior of the dry continent is dominated by sunny and cloudy weather. Even if there is fog, it is mostly radiation fog generated near the surface, which dissipates quickly, and the total annual precipitation is small. Due to the higher temperatures in low latitudes, which are conducive to evaporation, and the vast ocean waters, there are sufficient water sources, and the water vapor content in the atmosphere is very rich, often forming cloudy and rainy weather, with very abundant annual precipitation. On the contrary, in high latitudes, even if there is precipitation, , the precipitation is also very small, mostly snow.

In the vertical direction, the water vapor content near the surface is the largest. The higher you go to high altitudes, the less water vapor. Near the tropopause (10Km altitude), the water vapor content in the atmosphere is almost zero, and the atmosphere above the stratosphere is basically Contains no water vapor. Therefore, almost all weather phenomena in the atmosphere are concentrated in the troposphere, and there are almost no weather phenomena in the stratosphere and above.

2. Water vapor phase change and weather

The occurrence of all weather phenomena is actually the result of the movement of water vapor in the atmosphere and its phase change. As the air flow rises and falls or moves horizontally, the water vapor in the atmosphere will change from gaseous to liquid and solid due to temperature changes (mainly refers to the decrease in temperature), that is, water vapor condenses and sublimes, resulting in various weather phenomena. The main weather phenomena are: clouds, rain, snow, fog, dew, frost, hail, graupel, etc.

(1) Clouds and fog

Clouds are condensations formed by water vapor in the air, and are mainly composed of water droplets, supercooled water droplets and ice crystals. In terms of material composition, they can be divided into three categories: water clouds, ice clouds and mixed clouds. Clouds are the basis of precipitation and the intermediate link in the water cycle on the earth. Certain cloud shapes often appear with certain weather conditions, so clouds have certain indicative significance for weather changes. Fog is water droplets and ice crystals suspended in the air near the ground. When there is sufficient water vapor in the air and reaches saturation, the water vapor condenses to form clouds. The more abundant water vapor is, the wider the range and thickness of clouds formed.

The formation of clouds and fog greatly reduces the transparency of the atmosphere, weakens the solar radiation reaching the surface, and prevents the temperature from rising too high during the day. For example, the temperature is often lower on cloudy days; at the same time, it enhances the atmospheric reverse radiation. , which has a certain thermal insulation effect on the ground, especially at night. It often feels warmer on cloudy nights. The effect of clouds on surface temperature is shown in Figure 10-1. In short, the formation of clouds and fog changes the surface temperature and reduces the diurnal temperature range. The temperature during the day does not rise too high and the temperature does not drop too low at night.

Figure 10-1 Schematic diagram of the effect of clouds on surface temperature

(2) Rain and snow (precipitation)

Rain refers to falling from clouds to Liquid water droplets on the ground's surface, and snow refers to solid ice crystals that fall from clouds. Different clouds have obvious differences in the form, intensity, and nature of precipitation due to their different horizontal range, cloud height, cloud thickness, cloud water content, cloud temperature, and updraft. 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 low latitudes are higher than high latitudes; the form of precipitation is related to the temperature, and low latitudes Liquid rainfall is dominant, while solid snowfall is dominant at high latitudes.