Meteorology Lenka Petrov 1 Definitions Meteorology Study of

Meteorology Lenka Petrášová 1

Definitions • Meteorology – Study of the atmosphere & the processes that causes weather • Weather – State of the atmosphere at a particular place & time. Described by T, Humidity, Ppt. , Wind speed • Climate – Average values of weather conditions at some place for at least 30 years • Climatology – Study of climate, control, spatial and temporal variability 2

Climatic Zones 3

Atmosphere • Mixture of gases surrounding the earth • Devided into layers • Troposphere: surface to 36 000 ft - where most of weather is -Tropopause- top of troposphere, jet stream, turbulence, top of thunderstorms Stratosphere: to 160 000 feet 4

Composition of the atmosphere • Gases - Nitrogen 78% - Oxygen 21% - Other 1% - Water vapour 0% - 4% • Pollutants 5

On the Weather Maps • Isobars- lines which join the points of equal atm. pressure, identify pressure systems • Low pressure • High pressure • Trough of low (brázda) • Ridge of high (hřeben) 6

Fronts Symbols on map Boundaries between air masses • COLD- where cold air is overtaking warm air • WARM- where warm air is overtaking cold air • OCCLUDED- when a warm and cold front meets and the warm air is forced up above ground level • STATIONARY- when a warm or cold front stops moving 7

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Clouds • Amount of clouds: Sky cover- sky clear (no clouds); few (1/8 -2/8 cloud cover); scattered (3/8 -4/8); broken clouds (5/8 -7/8); overcast (8/8) • Gouped into 3 levels: – Low level: surface to 6500 ft( stratus, cumulus) – Medium level: 6500 - 20 000 ft AGL (altostratus, altocumulus, cumulonimbus) – High level: above 20 000 ft AGL ( cirrus, cirrostratus) 9

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Meteorological phenomena • Precipitation (rain, hail, snow grains, sleet, flurry, blizzard, whiteout) • Wind ( windshear, gust, squall, breeze, jet streams) • Mist- vizibility more than 1 km • Fog- vizibility less than 1 km • Humidity- the amount of water in the air • Dew point- the temperature to which air must be cooled before water vapour turns back to water 12

Danger for flight • Turbulence- Turbulence is caused by the relative movement of disturbed air through which an aircraft is flying -arise from strong wind over irregular terrain or obstacles, air movements associated with convective activity (thunderstorms and lightning) 13

• CAT- Clear Air Turbulence is defined as turbulence which is NOT associated with cloud and therefore cannot be detected visually or by conventional weather radar. - caused by flow of air in an unstable atmosphere • Source of CAT could be a JET STREAM- high level wind which is important to navigation because it blows more than 200 knots -> reduce fuel consumption - generated as a result of the temperature gradient between air masses 14

• Icing - Icing conditions exist when the air contains droplets (kapičky)of supercooled liquid water - Removal: a) If there is ice prior to take off on an aircraft: - Application of deicing fluid - Use of infrared heating b) In flight: - Electrical heating - pneumatic deicing boots ( inflated rubber which breaks the ice) - hot air from compressor 15

• METAR- Aerodrome routine meteorological report • TAF- Aerodrome forecast • NOTAM- a notice containing information concerning the establishment, condition or change in any aeronautical facility, service or procedure • SIGMET- information concerning en- route weather which may affect the safety of aircraft operations 16

Used sources: www. skybrary. aero Keller, Ladislav. Učebnice pilota 2008 17