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ATPL - BGS [Mod 1] Meteorology > 16. Pressure Systems > Flashcards

16. Pressure Systems Flashcards

1
Q

Pressure Systems

  1. The level of mean non-divergence is approximately ____hPa, ____ft
  2. This is called the ____level
A
  1. 600 hPa / 14,000 ft
  2. BAROSTATIC LEVEL

  • At this level the pressure system is neither high or low, but between the two

BAROSTATIC LEVEL

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2
Q

Pressure Systems

The barostatic level can be as low as 10,000ft (700 hPa) over which 2 geographic locations

A
  1. POLES
  2. SIBERIA

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3
Q

Pressure Systems

  1. High pressure systems are called CYLCONES or ANTI-CYCLONES and turns CLOCKWISE or ANTI-CLOCKWISE in the NH
  2. Low pressure systems are called CYCLONES or ANTI-CYCLONES and turns CLOCKWISE or ANTI-CLOCKWISE in the NH
A
  1. ANTI-CYCLONES / CLOCKWISE
  2. CYCLONES / ANTI CLOCKWISE

  • In Southern Hemisphere, the direction of turn changes so if clockwise, now anticlockwise, and visa versa.
  • The type of cyclone stays the same and name does not change

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4
Q

Pressure Systems

  1. The vertical spacing of the isobars in a WARM ANTICYCLONE aka a WARM HIGH are GREATER or SMALLER than surrounding isobars
  2. The vertical spacing of the isobars in a COLD ANTICYCLONE aka a COLD HIGH are GREATER or SMALLER than surrounding isobars
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5
Q

Pressure Systems

  1. Sub-tropical anticyclones is found typically around what latitudes
  2. This belt of anticyclones is sea based but can encroach onto land masses in WINTER or SUMMER
  3. The name of a good example of a warm high is ____
A
  1. 30° N and 30° S
  2. WINTER
  3. AZORES HIGH

  • Sun heats equatorial regions making air rise to tropopause
  • Air then flows out towards the poles
  • At around latitude 30° the air sinks down towards the surface, warming in the subsidence, producing a tenoeratyre ubversuib at kiw keveks aka WARM ANTICYCLONES
  • Can encroah onto land masses in winter of the hemisphere when the land surface cools

WARM ANTICYCLONE

SURFACE PRESSURE TYPES

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6
Q

Pressure Systems

  1. Cold Anticyclones are formed when the COLD or WARM surface temperatures make the lower tropshere WARM AND WET or COLD AND DENSE
  2. The name of a well known cold anticyclone is ____
  3. The change between upper and lower pressures can occur as low as ____ft
A
  1. COLD AND DENSE
  2. SIBERIAN HIGH
  3. 10,000 ft

  • Extremely low surface temperatures as low as -40℃ produce a pool of dense cold air and temperature inversion at the surface
  • Cold air pools are more prevalent over land than voer sea
  • Greatest activity of instability occurs when there is the greatest temperature contrast between the cold air at mid and upper levels and the air at the surface
  • Surface atmospheric heating is greatest around 2pm

COLD ANTICYCLONE

SURFACE PRESSURE TYPES

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7
Q

Pressure Systems

In a Siberian High aka a Cold High (Cold Anticyclone) pressure system, the wind at the surface will flow CLOCKWISE or ANTICLOCKWISE where as at altitude, it will flow CLOCKWISE or ANTICLOCKWISE

A
  1. CLOCKWISE
  2. ANTICLOCKWISE

  • A Cold High will have a low pressure at altitude, as air is converging and sinking, and a high pressure at the surface
  • Low pressure systems have anticlockwise rotation in the NH and high pressure systems have clockwise rotation in the NH

COLD ANTICYCLONE

SURFACE PRESSURE TYPES

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8
Q

Pressure Systems

A polar high pressure region is formed by COLD or WARM surface temperatures and SUBSIDENCE or LIFTING of air in the general circulation.

A
  1. COLD SURFACE TEMPERATURE
  2. SUBSIDENCE

  • Cold air aloft is subsiding onto cold air at the surface, but the aloft air is colder than the cold air at surface

COLD ANTICYCLONE

SURFACE PRESSURE TYPES

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9
Q

Pressure Systems

Temporary cold anticyclones form in the COLD or WARM are on the POLEWARD or TROPICAL side of a Polar Front, often in the shape of RIDGES OF HIGH or TROUGHS OF LOW pressure

A
  1. COLD
  2. POLEWARD
  3. RIDGES OF HIGH

COLD ANTICYCLONE

SURFACE PRESSURE TYPES

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10
Q

Pressure Systems

Anticylones are;

  1. LARGE or SMALL, sometimes ____nm across
  2. They are FAST or SLOW to form and dissipate
  3. They are SLOW or FAST moving
  4. Surface pressure gradients are SLACK or TIGHT creating LIGHT or STRONG winds at the surface
  5. The weater will be WET AND ROUGH or FINE AND CALM
  6. Solar heating may produce instability at low level and may lead to what type of clouds
A
  1. LARGE / 1500 nm
  2. SLOW
  3. SLOW
  4. SLACK / LIGHT
  5. FINE AND CALM
  6. FAIR WEATHER CUMULUS

  • If an Anticyclone forms over sea or moisture sources, there will be a tendancy for fog to form below the inversion
  • Surface outflow (divergence) is linked in both warm and cold types of subsidence. There will be little if any cloud and precipitaton early in the day

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11
Q

Pressure Systems

Cyclones are;

  1. LARGE or SMALL, sometimes ____nm across
  2. They are FAST or SLOW to form and dissipate
  3. Surface pressure gradients are SLACK or TIGHT creating LIGHT or STRONG winds at the surface
A
  1. SMALL / 300 nm
  2. FAST
  3. TIGHT / STRONG

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12
Q

Pressure Systems

Depressions can be classified by the way they form. Marry up each of the types of depression to the description;

  1. Formed along the line of the polar front [ ]
  2. Sometimes called Lee Depressions, formed by the swirling of the airflow behind hills and mountains [ ]
  3. Caused by surface heating [ ]
  4. Sometimes called polar lows, associated with small-scale instability developing in polar airflow [ ]
  • Thermal Depression
  • Cold Air Lows
  • Frontal Depression
  • Orpgraphic Depression
A
  1. Formed along the line of the polar front [FRONTAL DEPRESSION ]
  2. Sometimes called Lee Depressions, formed by the swirling of the airflow behind hills and mountains [OROGRAPHIC DEPRESSION]
  3. Caused by surface heating [THERMAL DEPRESSION ]
  4. Sometimes called polar lows, associated with small-scale instability developing in polar airflow [COLD AIR LOW ]

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13
Q

Pressure Systems

An orographic depression;

  1. Will occur on the WINDWARD or LEEWARD side of the mountain barrier
  2. Occurs when air is flowing PARALLEL or RIGHT ANGLES to the mountain barrier
  3. After crossing the mountain barrier the air will CONTRACT or EXPAND
A
  1. LEEWARD
  2. RIGHT ANGLES
  3. EXPAND

  • Air layer is a certain thickness but then reaches the mountain barrier
  • The air is “squashed” as it passes over the barrier at a right angle
  • As it passes across, the air expands back to the original thickness as on the upstream side of the mountain
  • This rapid expansion develops a strong sping around the vertical axis
  • Common known places this occurs are Rockymountains (east side)

OROGRAPHIC DEPRESSION

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14
Q

Pressure Systems

  1. Thermal lows form when the surface is COLD or WARM
  2. Thermal Lows form over LAND or WATER in WINTER or SUMMER
  3. Thermal lows core temperature is WARMER or COLDER than then surrounding environment
A
  1. WARM
  2. WATER / WINTER
  3. WARMER

  • Therma lows are warmlows, with cores warmer than the environment
  • Thermal lows form over water in winter, when water temperature is often substantially higher than surrounding land

THERMAL LOW

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15
Q

Pressure Systems

What type of weather is characterised with a Polar Low when it forms over oceans on the poleward side of a polar front at very high latitudes

A

BLUSTERY SNOWY CONDITIONS

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16
Q

Pressure Systems

Cold lows can be classified as warm or cold lows pdeending on whether the core at a particular level is warmer or colder than the surrounding environment.

  1. Frontal depressions are typically WARM or COLD surface lows
  2. Cold lows can exist at height when high level POLAR or TROPICAL air extends into temperate regions. This is known as a high level cold low
A
  1. COLD SURFACE LOW
  2. POLAR

  • The core of a cold low is colder than the surrounding environment
  • Higher latitude colder air extending into temperate regions sliding over warmer air can cause a high level cold low
  • This typically happens around mountains

COLD LOW

HIGH LEVEL COLD LOW

SURFACE PRESSURE TYPES

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17
Q

Pressure Systems

  1. When cold polar air extends into temperate regions, this can form a high level cold low. This is also known as what
  2. At height, high level cold lows are STABLE or UNSTABLE
  3. At surface, cold lows are STABLE or UNSTABLE
A
  1. COLD AIR OUTBREAK
  2. UNSTABLE
  3. STABLE

  • A cold air outbreak at height is unstable. Warm below and cold alof equals a high lapse rate

11/12

18
Q

Pressure Systems

A air mass thickness chart will show the thickness of air masses between 2 pressure levels, 1000 hPa (surface level) and 500 hPa (18,000 ft).

Refer to the following diagram. The region with the least air mass thickness is signified by which colour

A

BLUE

  • Remember when looking at this diagram, that the colours are representing a thickness layer between 1000 hPa and 500 hPa.
  • If blue, this means that contour lines when seen from side profile would be packed closer together
  • Orange shades represent further spaced apart contour lines when viewed from side profile

12

19
Q

Pressure Systems

  1. A ridge of high pressure is typically associated with FAIR SETTLED or UNSETTLED weather
  2. A trough of cold pressure is typically (not always) associated with FAIR SETTLED or UNSETTLED weather
A
  1. FAIR SETTLED
  2. UNSETTLED

13

20
Q

Pressure Systems

  1. TROUGHS or RIDGES typically coincide with fronts
  2. TROUGHS or RIDGES are typically associated with cloud conditions, precipitation and lines of convective cloud and thunderstorms
A
  1. TROUGHS
  2. TROUGHS

13

21
Q

Pressure Systems

The name of a region between 2 highs and 2 lows

A

COL

  • Cols produce virtually no low level wind

COL

13

22
Q

Pressure Systems

  1. Cols over land in winter are associated with what sort of weather conditions and phenomenon
  2. Cols over land in summer are associated with what sort of weather conditions and phenomenon
A
  1. DETERIORATING VISIBILITY / RADIATION FOG
  2. CONVECTIVE ACTIVITY / THUNDERSTORMS

COL

13

23
Q

Pressure Systems

A cold air pool aka Cold air drop is a term applied to cold are which what in particular

A

HIGH VERTICAL EXTENT

  • Appreciable vertical extend that has been isolated in lower latitudes as part of the formation of a cut off low
  • can be easily seen as an area of low pressure aloft

14

24
Q

Pressure Systems

A cold air pool in summer will typically be associated with what sort of weather

A

SHOWERS and PRECIPITATION

  • In summer, cold air pools which lie over land become unstable due to the heating of the air in the lower layers near the surface
  • This results in developed convective clouds in the region of the cold air pool, accompanied by showers and precipitation
  • The heating is dependant on solar radiation, which can only occur during the day, so convective pattenrs follow a pattern with greatest activity in the afternoon
  • Cold air pools can be weather active for several days, sometimes a week

14

25
Q

Pressure Systems

  1. The greatest convective activity associated with a cold air pool occurs at what time of the day
  2. This is due to a dependance on what in regards to heating the lower layers of air
A
  1. AFTERNOON
  2. SOLAR RADIATION

  • In summer, cold air pools which lie over land become unstable due to the heating of the air in the lower layers near the surface
  • This results in developed convective clouds in the region of the cold air pool, accompanied by showers and precipitation
  • The heating is dependant on solar radiation, which can only occur during the day, so convective pattenrs follow a pattern with greatest activity in the afternoon
  • Cold air pools can be weather active for several days, sometimes a week

14

ATPL - BGS [Mod 1] Meteorology (27 decks)

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