§ 35. Rainfall (textbook)

§ 35. Atmospheric precipitation


What precipitation in your area at different times year?


In liquid water (rain, mist) or solid (snow, hail) states that falls from clouds or released from the air on the Earth's surface (fog, dew, frost, hoarfrost)  called precipitation.

Formation precipitation. Cloudy weather is often, but not always fall at the same time Air. So what is needed for their formation? If the cloud is very small kraplynky water or ice crystals (less than 0,05 mm) it will not rain. While they are small and light, then held high above ground rising flow of air. Under certain conditions kraplynky face and merge into larger drops. The clouds darken and become blue-black. Big drop (0,1-7 mm) can no longer stay in the air and fell, creating rain. Hair rain often accompanied the storm.

Snow formed in clouds that at temperatures below 0 0C consist of crystals dribnesenkyh-holochok, connecting in snowflakes. Snow falls in winter in temperate latitudes and in polar - year round. It forms on the Earth's surface snow. Its thickness is in the temperate latitudes 30-50 cm and the mountains - a few meters. Snow covers the field like a blanket, vberihayuchy winter crops from winter kill. It contains large reserves of water that spring feeding the river fills the damp soils and adds groundwater.

Hail formed when warm air rises up quickly. It picks up the clouds and rain carries them to a height where the temperature decreased to -10 0C. At this drops freeze and become icy in the balls - hradynky. They are size from 1 mm to the size of chicken eggs. Record high in the world was hailstone weighing 7 kg, fell during the hail in China (1981), and in Ukraine - 500 gr. (1960). Hailstone weighing 3 kg elephant killed in India (1961). Falling from high speed, hailstones are not able to melt, despite the high temperature near the ground. Hail causes considerable losses: destroys crops and fruits breaks branches of trees, sometimes kill small animals and damaging roofs.

Depending on humidity, types of clouds, speed wind, precipitation are oblozhni (Uniform and durable) storm (Strengths and short-term) mryachni (Very small as semolina).

Fig. After the snowfall


Rosa, frost, hoarfrost. Rainfall can "fall out" and just the air. This happening on the ground in chilled osculation it with air, saturated moisture. 

Dew - Drops of water, which sometimes covered with earth and plants. It  formed after the event Sun, when the surface of the earth and the air around it quickly cooled. COLD air can no longer hold as much water vapor as maintained in the afternoon at higher temperatures. Its excess condenses into droplets of dew.

In the cold season (at temperatures below 0 0C) instead of dew formed a thin layer of ice crystals - frost. You can see the fall or early spring. Hoarfrost puffy ice crystals grows on trees and other subjects.

Measurement rainfall. At the weather station measured rainfall for opadomira help. Opadomir - A cylindrical bucket where you are going to Air. To wind not blown snow ohorodzhuyut it. Water poured from a bucket in measuring cup. According to the graduated walls of glass layer determines the height of precipitation (in mm). If snow falls, the opadomir contribute to a warm room. For example, one layer allows light rain 1-2 mm of water, and cataract - 40 mm. When the snow melts, measured height water layer. So opadomirom measured layer of water that would have arisen in the area for Earth's surface if the water will not divalasya: not flowed, not in prosochuvalasya ground or evaporated. The rainfall for the month equals the sum of all days of the month. Total precipitation for all months gives the annual rainfall. Thus, the average annual rainfall in Kiev - 600 mm.

Meteorologists also measure the height of snow cover. Such  measurements do snihomirnoyu rail, divided into centimeters.

Distribution precipitation around the globe. Atmospheric Air on the planet unevenly distributed. It depends on geographical provision of terrain and prevailing winds. Most rainfall in equatorial (more than 2 000 mm) and moderate (800 mm) widths. Little rainfall (200 mm) falls in the tropical and polar latitudes. However, this distribution disturbed nature of the earth's surface: the ocean rainfall more than over land. In the mountains much more rain "adopt" those slopes that address to prevailing winds. Yes, Ukraine Windward slopes of the Carpathians to receive 1500 mm year, and the Leeward - half -750 mm.

Record high annual rainfall on Earth had in village Cherapundzhi, that at the foot of the Himalayas - 23 000 mm. A very rainy place on the planet considered HawaiiWhere 335 days a year is the rain, which brings 12 000 mm water. Record arid  places where the precipitation is falling for years, is Desert Atacama South America (1 mm per year) and Sahara Africa (5 mm per year).

Annual rainfall distribution charts show.


Fig. The distribution of precipitation around the globe


Questions and Tasks

1. Name precipitation on the Earth's surface clouds in the liquid and solid form.

2. What damage can cause hail?

3. As frost and dew formed?

4. How to measure rainfall?

5. Consider why the main "supplier" of precipitation called the World Ocean, and the main "engine" of the process - the Sun.