Pressure Systems Flashcards
What are Isobars?
How are they created?
Lines of equal pressure.
Weather station pressures are converted to (using ISA) to sea level. Points are then joined up using lines and plotted.
What is the pressure difference between isobars
4 Hectopascals +- 1000
What do closer isobars indicate?
High pressure gradient therefore stronger wind
What direction do does the air around Depressions and Anti - Cyclones rotate?
NH and SH respectively
NH: Depression Anti Clockwise and Anti Cyclone Clockwise
SH: Anti- Clockwise and Anti Cyclone Clockwise
Do anti cyclones produce Cloud?
Yes but mostly absent
IS visibility good in an anti cyclone?
There can be poor visibility due to subsidence producing anti cyclonic gloom
Subsidence inversions stop what? 3
Convention currents, preventing lifting cooling and cloud formation
What is the damping effect and effect on weather
Convergnce aloft produces widely spaced isobars with quite dry weather. Haze can reduce vis
Descending air in a high causes?
Air descending is warmed by adiabatic compression. Resulting ion low RH, the descending air may not reach ground causing a most layer near surface.
Cold Anti cyclone caused by? Shape
cold surfaces causing low level contraction of air. Weaker at altitude
Flat Upper Contour
Warm Anti Cyclone Caused by?
Shape?
Convergence in the upper atmosphere
“Dome Shaped”
Ridge and associated weather???
Wedge shaped extension of a high pressure
Similar weather to high pressure, fair weather.
Trough and Weather?
+ Bonus
Extension of low pressure with similar weather.
Between two highs can also be a trough
Col?
Slack pressure between a high and a low
Fog low cloud, quiet weather rain if frontal
Falling barometer is a sign of?
Area of depression or low
