ATS 553
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Why is the Winter Why is the Winter Hemisphere Hadley Hemisphere Hadley Circulation stronger Circulation stronger than the Summer than the Summer Hemisphere Hadley Hemisphere Hadley Circulation? Circulation? ATS 553 ATS 553
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Why is the Winter Hemisphere Hadley Circulation stronger than the Summer Hemisphere Hadley Circulation?. ATS 553. Based on:. “Role of Continents in Driving the Hadley Cells”, by Kerry H. Cook, Journal of the Atmospheric Sciences , 1 April 2003, 957-976. In Intro, you learned…. - PowerPoint PPT Presentation
Transcript of ATS 553
Why is the Winter Why is the Winter Hemisphere Hadley Hemisphere Hadley
Circulation stronger than Circulation stronger than the Summer Hemisphere the Summer Hemisphere
Hadley Circulation?Hadley Circulation?
ATS 553ATS 553
Based on:Based on:
““Role of Continents in Driving the Role of Continents in Driving the Hadley Cells”, by Kerry H. Cook, Hadley Cells”, by Kerry H. Cook, Journal of the Atmospheric SciencesJournal of the Atmospheric Sciences, , 1 April 2003, 957-976.1 April 2003, 957-976.
In Intro, you learned…In Intro, you learned…
Maybe you even learned…Maybe you even learned…
Northern Hemisphere SummerNorthern Hemisphere Summer
Maybe you even learned…Maybe you even learned…
Southern Hemisphere SummerSouthern Hemisphere Summer
However, Ramage shows…However, Ramage shows…
Northern Hemisphere SummerNorthern Hemisphere Summer
However, Ramage shows…However, Ramage shows…
Southern Hemisphere SummerSouthern Hemisphere Summer
So the question is…So the question is…
Why is the Hadley Circulation so Why is the Hadley Circulation so strong in the WINTER Hemisphere?strong in the WINTER Hemisphere?
But a better question is…But a better question is…
Why is the Hadley Circulation so Why is the Hadley Circulation so WEAK in the SUMMER Hemisphere?WEAK in the SUMMER Hemisphere?
Strength of the Hadley Circ.Strength of the Hadley Circ.
Described Described by the low by the low level level meridional meridional windswinds
But first, let’s talk about trade But first, let’s talk about trade winds.winds.
Sum
mer
Sum
mer
Maintaining trade windsMaintaining trade winds
frictionvft
u
0
What determines friction?What determines friction?
frictionvft
u
0
What determines friction?What determines friction?
frictionvft
u
0
Summer hemisphere has weaker trade winds, so friction is less.
What determines friction?What determines friction?
frictionvft
u
0
If friction is smaller, what happens to f times v?
What determines friction?What determines friction?
frictionvft
u
0
Therefore, the v component has to be smaller!
What determines friction?What determines friction?
frictionvft
u
0
Therefore, the Hadley Circulation has to be smaller in the Summer Hemisphere!
Temptation:Temptation:
To say that it must just be the To say that it must just be the opposite in the Winter Hemisphere:opposite in the Winter Hemisphere:
““In the summer hemisphere, heat In the summer hemisphere, heat lows over continents result in a weak lows over continents result in a weak meridional pressure gradient force, meridional pressure gradient force, weak trade winds, and a weak weak trade winds, and a weak Hadley Circulation.”Hadley Circulation.”
Temptation:Temptation:
To say that it must just be the To say that it must just be the opposite in the Winter Hemisphere:opposite in the Winter Hemisphere:
““In the summer hemisphere, heat In the summer hemisphere, heat lows over continents result in a weak lows over continents result in a weak meridional pressure gradient force, meridional pressure gradient force, weak trade winds, and a weak weak trade winds, and a weak Hadley Circulation.”Hadley Circulation.”
Temptation:Temptation:
To say that it must just be the To say that it must just be the opposite in the Winter Hemisphere:opposite in the Winter Hemisphere:
““In the In the winterwinter hemisphere, hemisphere, polar polar highshighs over continents result in a over continents result in a strongstrong meridional pressure gradient meridional pressure gradient force, force, strongstrong trade winds, and a trade winds, and a strongstrong Hadley Circulation.” Hadley Circulation.”
However…However…
That’s not how it works in the Winter That’s not how it works in the Winter Hemisphere.Hemisphere.
Polar highs are VERY VERY shallow Polar highs are VERY VERY shallow features, with almost no impact on features, with almost no impact on the meridional pressure gradient the meridional pressure gradient force.force.
