What are suspended particles in the air?

Answer 1

More than human economic activities produce greenhouse gases, but also to create a large amount of suspended particles. They have a cooling effect on the atmospheric radiation and the net effect of greenhouse gases the contrary. Suspended particles are floating in the air of small particles (diameter between 0.001 ~ 10μm) a general term, has the natural and man-made. Natural suspended particles have ash, flue dust (soil dust; most from North Africa and the Asian desert areas), sea salt aerosol and so on. Man-made industrial dust suspended particles have (industrial dust; mostly produced by incomplete combustion of impurities), soot, sulfate and nitrate and other suspended particles.

Larger sizes of suspended particles by the gravity traction quickly dropped the surface, stay in the atmosphere is very short, little impact on climate. Small particles of suspended particles, although the largest quantity, but quality and the proportion of surface area is too small, the impact on climate is not much. Therefore, the impact of climate biggest diameter of suspended particles around in between 0.1 ~ 1μm.

Suspended particles absorb radiation, and scattering of solar radiation. Suspended particles in the presence of a high temperature may rise, other regions are cooling. For example, near the surface of soot absorbed short-wave radiation, so that tropospheric warming, but the surface absorption of solar radiation has decreased, the temperature drop. In another example, the stratospheric volcanic ash in the absorption of atmospheric long-wave radiation, so that stratospheric temperature rise, but its strong scattering effect, increase the albedo, reducing the troposphere into the amount of solar radiation, anti-so near the surface temperature dropped. Generally speaking, the majority of suspended particles (apart from soot) imposed on the radiation effects of the troposphere for the cooling effect.

Another role of suspended particles is to serve as cloud condensation nuclei . Water vapor are less than the look, we can see the clouds are water droplets or ice crystals to form. Small water droplets to form cloud condensation nuclei to have it the size of about 0.1 ~ 0.2μm, and we consider the size of suspended particles. Once generated, the small droplets can be formed within minutes of raindrops 2000μm. By volume, the growth of a 1012-fold. Even if there are no impurities, water vapor will reach saturation point, if condensation. However, impurities (such as salt, suspended particles, etc.) exist, allows water vapor did not reach saturation condensation began (just as easy to damp salt caking). For example, a small droplet radius of 0.4μm, if melting has 10-15 grams of salt, the water droplet surface is equivalent to the volume of saturated water vapor relative humidity of 99.6%. That is to say, this one small water droplets can not saturated in water vapor environment, the lessons of the water vapor around constantly growing larger. Once the water vapor in the air condenses into small droplets together to form visible clouds.

With many suspended particles on the characteristics of cloud condensation nuclei, they can increase Xiaoyun droplet (cloud droplet) the quantity, but a further increase in cloud albedo. Consider the equivalent amount of water vapor, if the cloud droplet number, each assigned to a cloud droplet of water vapor less cloud droplet size also small; the other hand, if a small number of cloud droplets, the cloud droplet size larger . Generally speaking, the smaller cloud droplets, cloud albedo larger. In addition, the small size of the cloud droplet formation of precipitation is not easy, because they are too light, but probably would not fall, the decline may also be the way to quickly evaporated.

Increase in atmospheric aerosol content, which may result in the following effects: clouds within the cloud droplet increase in the number, size small is not easy to form precipitation, cloud lifetime is therefore variable length. The Earth's average albedo of 0.3, in which contributions to clouds of 0.2. If the atmospheric cloud cover and cloud albedo increase, and longer life, the Earth's albedo may be larger. In other words, the atmosphere and surface absorbs less solar radiation. From the above discussion, we know that excessive suspended particles serve as condensation may wish to check the indirect effects of the Earth's atmosphere are cooling radiation may make the troposphere and surface temperatures lower. However, can not be denied is that the scientific community of suspended particulate understanding the indirect effects are still quite limited.

Different greenhouse gases in the atmosphere of a long lifespan, within the troposphere aerosol lifetime is only around a week. Once they enter the troposphere, and some by the influence of gravity falling ground, and some dissolved in rainwater, and the formation of acid rain. Greenhouse gases and long lifespan, so that it can send with the atmospheric circulation evenly spread around the world. Suspended particles due to the short lifespan, can be transmitted is not long distance, mostly scattered in the vicinity of regional pollution sources. Therefore, the distribution of it are regional rather than global. Characteristics of this one can clearly suspended particles from man-made sulfate content distribution maps to see: the areas with the highest concentration in the northern hemisphere, such as the eastern United States, Europe and China, the Southern Hemisphere is much smaller than the Northern Hemisphere content content.

Answer 2

Air pressure is caused by gravity acting on suspended particles in the air.

Answer 3

Suspended particles in the air are called aerosols. They can reflect the sun's heat and cool the atmosphere. They can also absorb the sun's heat and warm the atmosphere.

Answer 4

air pressure