Hazardous weather phenomena for aviation
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Hazardous weather phenomena for aviation

Hazardous weather phenomena for aviation

Fog - The phenomenon when airborne water droplets or ice crystals to reduce the visibility of the 1 and less.

The mist is formed by the condensation of water vapor in the vicinity of the Earth's surface. According to its physical nature is similar to the fog cloud. Often one phenomenon into another. For example, when a fog rises, it is converted into low pannus stratus. Conversely, clouds, falling to the ground, are perceived as a phenomenon of fog.

The formation of fog due mainly to the cooled surface air, so depending on how the process of air cooling mists are divided into three types: radiation, advective, frontal.

Radiation fog is formed due to cooling of the surface of the earth and the adjacent layer of air, with an inversion of temperature and, with sufficient humidity, a surface fog, called radiation, is formed. The greatest frequency of radiation mists occurs at night, when there is no inflow of solar radiation, and the earth's surface and air lose heat as a result of radiation. Radiation fog is the most dense near the surface of the earth and visibility here often deteriorates to several tens of meters. With the height, the density decreases, and from the altitude of the flight the earth is seen through it well. With the rising of the sun (the beginning of warming up), the radiation mist, as a rule, dissipates.

Advective fog is formed by cooling with respect to warm and moist air moving over a colder underlying surface. In winter, advective fog is formed, as a rule, in the air mass moving from the ocean to the continent; In summer - from the mainland to the ocean. Advective fog, unlike radiation, arises at more significant wind speeds at the surface of the earth, which are most often 4-8 m / s, but it can also form with a stronger wind reaching 12-15 m / s. A feature of advective fog is also an increase in density with height. At the same time, the visibility at the surface of the earth can be quite satisfactory, but it is worthwhile to climb several tens of meters (30-50 m), as the horizontal visibility completely disappears.

Advection fog can be formed in any part of the day and preserved for a long time.

Front fog - Mist arising on the atmospheric fronts. They come in three types: pre frontal, frontal and zafrontalnye.

Prefrontal fog formed due to moisture saturation of cold air, which is under the front surface.

The most favorable conditions for the formation of prefrontal fog, rain falls when the temperature is much higher than the temperature of cold air, which is located near the surface of the earth.

Front t u m I arises directly during the passage of the front. This fog is a cloud frontal system extending to the earth's surface, most often observed during the passage of fronts over the hills.

Zafrontalny th mist is formed directly after the passage of a warm front and a warm occlusion. Education zafrontalnogo fog is not much different from the conditions of formation of advection fog.

In addition to the above, the main, the most common, types of fog, and there are others, such as:

  • advection-radiation;

  • fogs slopes;

  • fog fumes;

  • frost or ice fog.

Snowstorm - The transfer of snow on the ground by the wind is strong enough. There are three types snowstorm: drifting snow, blowing snow and blizzard total.

Drifting - The transfer of dry snow, the wind just above the snow surface. Drifting occurs at a wind speed-4 6 m / sec, while the snow rises to a height of several tens of centimeters.

Blowing snow - A phenomenon similar to drifting snow, stand only difference is that it happens in a strong wind. When blowing snow snow rises to a height of several meters.

How drifting and blowing snow impair visibility in the lowest layers of the atmosphere.

Hazardous weather phenomena for aviation

Total storm is characterized by a strong wind that lifts the snow from the earth's surface and snowfall from the clouds.

Dust storm - A phenomenon similar to blowing snow, but with the only difference being that the dust storm is in the southern steppes and deserts, mainly in the summer, when a strong wind from the surface rise sand particles or dust which, clouding the atmosphere, dramatically impair visibility.

Vertical power of dust storms can be very razlichnoy- from a few tens of centimeters (dust and sand drifting snow) up to several tens or even hundreds of meters.

Storm - Atmospheric phenomenon in which there are multiple electrical discharges (lightning), between clouds or between clouds and the ground, accompanied by an audible phenomenon - thunder. Usually, when there are storm rainfall in the form of rain, hail and very rarely in the form of snow.

Sometimes there thunder and rain; they are known to have H & M and thunderstorms.

Thunderstorms come in two basic types: vnutrimassovye and front.

Vnutrimassovye storms formed in the wet and

the air inside the stable air masses. The most common vnutrimassovoy storm is thermal, or m s t and I storm resulting from heating the air from the underlying surface. Heat storms occur in summer in the afternoon and in the evening scattered. Viutrimassovye thunderstorms usually occur in isolation, or are located from each other at a distance of 20-30 km, so the aircraft is free to bypass them.

Frontal thunderstorms develop on the cold and warm fronts, as well as on the fronts akklyuzii.

Hazardous weather phenomena for aviation

Thunderstorms on cold fronts - The most powerful; they arise from the powerful lifting wedge warm air of cold air. As a result, in front of the cold front in the warm season, formed a powerful cumulonimbus (thunderstorm) clouds with showers, often with hail and squalls reaching hurricane strength.

Thunderstorms in the cold front are amplified in the afternoon and weakened in the second half of the night and morning.

Thunderstorms in the warm front - A relatively rare phenomenon; they develop in the heat unstable air ascending along the wedge of cold air. Cumulonimbus clouds are stratiform clouds are hidden. Characteristic of thunderstorms in the warm front is that they are the most active in the evening and night hours.

The danger for the aircraft and crew are powerful upward n downdrafts of air inside the cumulonimbus clouds and in close proximity to them, as well as a possible lightning strike on the plane.

City - Rain falling during the warmer months of the powerful cumulonimbus clouds in the form of dense particles of ice of various, sometimes very large sizes. Hail usually during a thunderstorm with heavy rain.

Flurry - A sudden and short increase in wind speed (more than 15 m / s), is accompanied by a change in its direction. Squalls occur in front of a cumulonimbus (thunderstorm) clouds. They can be seen as a dark, brooding, spinning shaft - "shkvalo- HICLES Gate", which is a vortex with horizontal axis.

Icing - Deposition of ice on the rigid parts of the aircraft, power plants and external details of his special equipment (antenna and so on. D.) During the flight in the air containing supercooled water droplets.

The most severe icing occurs in the clouds and in the part, where there is more water content and larger droplets. Practice shows that the most severe icing happen at temperatures of up to 0 -10 ° C and below. At very low temperatures in the clouds (-30 -40 °) severe icing occurs.

The intensity of ice deposits is considered to be weak ice when the ice is deposited at a rate of up to 0,01 0,5 mm / min, the average - from the 0,51 1,0 to mm / min and at a speed of strong deposits of ice more than 1,0 mm / min.

Icing hazards associated with the fact that the deposition of ice iskazhetsya profile shape of the wing and tail, which leads to a deterioration of the aerodynamic properties of the aircraft, the loss of its stability.

Aeronautical meteorology

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