Local Wind Systems Flashcards
what is the diurnal variation?
the suns heating effect on earth will vary throughout the day - heating the surface during the day and cooling at night. This variations causes changes in the way the air moves over the surface. These changes will follow a 24 hour cycle. this is called diurnal variation
How big is the diurnal effect at sea?
its very small due to a lack of convection current, but other unexpected air movements may occur when sea comes into contact with the coast.
the land has a lower Specific Heat’ than the sea and will therefore absorb the sun’s radiation at its surface, faster than the sea. Whereas the sea will take longer to heat up but will then retain its ‘Specific Heat’
for longer than the land? True or False
True
what is normally produced over the land after sunrise? and why?
a thin very warm surface layer is produced, as the solar heat energy is transferred to the surface air by contact through conduction and convection.
what is a sea breeze?
reduction in surface density causes a decrease in surface (barometric) pressure and the heated surface air then starts to ascend until it reaches a layer of equal density.
creating an area of higher Pressure over the land, typically at 2000 feet. The Pressure over the sea is now higher than the land surface Pressure, the Pressure Gradient (blowing from High to Low Pressure), causes a breeze to flow from the sea to the land, bringing the cooler denser air – this
is called a Sea Breeze
how does the continuous circulation pattern reinforce sea breeze?
The Circulation pattern is reinforced as air in the High-Pressure area above the land, flows towards the Lower- Pressure area above the sea and the colder air then descends to replace the air flowing towards the land.
what are the significant times of sea breeze?
The Sea Breeze starts at about 10 am, peaks at about 3 pm, and dissipates around sunset.
how fast can sea breezes get?
It can reach speeds of around 10 – 15 knots
how high and far can sea breezes get?
it can extend up to 3000 feet high and between 25 – 40 kilometers inland
what is the most associated cloud with sea breeze?
With continuous moisture carried inland from the sea to land, the associated cloud is Cumulus and often referred to as Fair Weather Cumulus
what happens to cloud formation in a sea breeze when there is a peninsular?
In areas where there is a peninsular, a Sea Breeze either side can develop, a convergence zone can then exist that raises the Cumulus into Towering Cumulus (TCu) or even Cumulonimbus (Cb)
is there any precipitation with a sea breeze?
no unless cloud formation conditions such as TCU or Cb exist.
what are flight conditions like in a sea breeze?
turbulent, even in mild conditions, expect a light to moderate turbulence and associated windshear, as you move from sea breeze to normal wind above the sea breeze or from a higher level into the sea breeze
how is land breeze formed?
At night, the land cools more quickly than the sea, because the land has a lower specific heat than the sea.
As air in contact with the land cools, a higher pressure develops above the land, and a lower pressure over the higher temperature – the sea’s surface.
This causes the direction of airflow to reverse, because at the surface the wind is now blowing from the land towards the sea.
how fast is land breeze usually and how does its speed reinforce the circulation of the land breeze?
The wind speed is around 3 - 4 knots. As a result, the air tends to move from the sea to the land at a
higher level and this reinforces the Land Breeze circulation in the lower layers