Pressure Systems Flashcards
What is a pressure gradient and how is it measured against isobars
Rate of change of pressure over given distance measured at right angles to isobars
What is an anti cyclone and which way does it rotate (SH)
High pressure area
Anticlockwise
What weather can be expected in an anticyclone and why
Good weather, due to subsidence(replacing of diverging air)
Cloud - little to none
Precip - none
Vis - poor, hazy(summer), foggy(winter)
Temp - hot in summer, cold in winter
Wind - light and variable
What are characteristics of warm anticyclones(subtropical highs)
Large area, elongated shape, deep vertical extent
Most often stagnant and strengthen with an increase in alt
What are characteristics of cold anticyclones(polar continental highs)
And how are they formed
Caused by low surface temps only over large land masses in winter
Tends to weaken with increase in alt and may turn into depression at high alt
Where are Travelling/Temporary cold anticyclones formed
In cold air along polar front between to polar front depressions
What is a blocking anticyclone
What latitudes can it be expected
Warm anticyclone; Slow moving air preventing faster moving pressure systems
Must be at higher lat than parent subtropical high - 45°- 65°
What are Ridges/Elongated High
And what weather can be expected
Neck/Ridge of high pressure with low pressure lying on either side
Weather generally fine-fair
What is a Col
What weather can be expected generally, and during summer and winter
Neutral region between 2 highs and 2 lows
Conditions normally settled, dependant on changing pressure;
Summer : extended Contact with hot ground cab lead to cloud/thunderstorms
Winter : extended contact with cold surface can lead to fog/low stratus
Gentle surface winds and generally quickly absorbed into other systems
What is a Thermal High and what causes it
Area of high pressure with shallow vertical extent
Produced primarily by cold surface temps
(1)What is a Depression
(2)What type of weather is associated with it
(3)Which direction does it rotate(SH)
(4)What front is usually associated with them
(1)Air mass with lower pressure than surrounding air
(2)Storminess and precipitation
(3)clockwise
(4)cold and warm fronts
What weather can be expected from cyclones
Cloud - full cover from near surface to tropopause
Precip - light to moderate, +SH and thunderstorms in unstable air
Vis - good out of Precip, poor in precip
Temp - mild
Wind - depends on isobar gradient but generally strong
What is a warm depression/thermal low
Cyclone with warm air in centre, with greater distance between pressure levels
What is a cold depression/dynamic low
Cyclone with cold air in centre
What is a secondary low
What weather can be expected from it in summer vs winter
Á secondary low pressure area that revolves around main center in anticlockwise direction
Associated with thunderstorms in summer and gales/heavy precip in winter
