Monsoon

• Mult. Choice Question

Monsoon

• Mult. Choice Answer

Asian Monsoon

• Best known monsoon is the Asian Monsoon
• In summer, India experiences very _____ sun angles being near the Tropic of ________
• Its land _____ ____ to very _____ temps
• This makes the air very ____ density and causes a ____ to form on land

Asian Monsoon—Fig. 7-11 (b)

Asian Monsoon—See Fig. 7-11 (b)

• Winds blow toward the Low
• So warm, moist air from the Indian Ocean is advected northward to India, bringing heavy precipitation
• This Low also draws the ITCZ northward

Asian Monsoon—Fig. 7-11 (a)

Asian Monsoon—See Fig. 7-11 (a)

• In winter, the Siberian High forms due to very cold, dense air in N Asia and causes divergence, so wind is blowing away from it down the Himalayas to India
• This is very dry air, so very little rain falls during the winter

Asian Monsoon

• So the Asian Monsoon is a seasonal wind that shifts from ________ winds in summer to ________ winds in winter
• Half the world’s population inhabits areas affected by the Asian Monsoon

North American Monsoon

• The SW US and NW Mexico experience a monsoon also
• It is milder than the Asian Monsoon, but still important
• The SW Monsoon brings a dry spring followed by a rainy summer (rainy as desert areas go) in this region

North American Monsoon—Fig. 7-13

North American Monsoon—See Fig. 7-13

• Similar to Asian Monsoon, in the summer, the SW US gets very hot, so the air is less dense and a Low develops
• This Low brings moist Pacific (and even Gulf of Mexico) air into the SW, forming precip

North American Monsoon—Fig. 7-12

Westerlies

• Remember how the mid-latitude winds aloft in the three-cell circulation model didn't fit with observations? Now we'll explain why.
• The Westerlies in the mid-latitudes are driven by the _______ contrast between the equator and the poles
• Cold, dense polar air is more ________
• Pressure decreases _______ with height at the poles

Westerlies

• So, if you’re at a certain height high in the troposphere, your pressure at that height over the ________ is going to be _____ than your pressure at that height over the _________
• This creates a pressure gradient at that height, with the PGF pointing toward the ________ (_______ pressure)

Westerlies—Fig. 7-14

Westerlies—See Fig. 7-14

• At first, the wind aloft then goes from equator to pole, but it gets turned by the Co to a west-to-east flow by the time it gets to the mid-latitudes
• Therefore, winds aloft are westerly in the mid-latitudes, not what the three-cell circulation model suggested

Westerlies

• The pressure gradient between the equator and poles we just discussed gets _______ the higher one goes in the troposphere
• This causes wind speeds to _________ with height above ground
• The ________ wind speeds will therefore generally be found just ______ the tropopause

Jet Streams

• Jet Streams: areas of _______ winds within the Westerlies in troposphere
• Usually located just _______ the tropopause and above surface _____ _________

Jet Streams

• Mult. Choice Question

Jet Streams—Fig. 7-16 (a)

Jet Streams

• Large __________ gradients at the surface translate into large __________ gradients aloft, which result in the _______ winds
• Polar jet stream is usually near the ______ front—the boundary between the cooler polar air (easterlies) and the warmer Westerlies air

Jet Streams—Fig. 7-16 (b)

Polar Jet Stream

• Polar jet stream has _______ winds in winter, when temp gradients at surface are _________
• Its position is farther ______ in winter also, due to polar air dipping farther ______

 Polar Jet Stream—Fig. 7-18

Polar Jet Stream—Fig. 7-15

Polar Jet Stream—See Fig. 7-15

• Notice since the jet stream is located above the largest surface temp gradients, colder air is on one side, and warmer air is on the other side

Polar Jet Stream—See Fig. 7-15

• If you are moving with the jet stream winds, colder air is to your left, warmer air to your right
• In our neck of the woods, this usually translates to us having cooler weather when the polar jet is to our south, and warmer weather when it's to our north

Subtropical Jet Stream

• In winter, there is usually a large enough ________ gradient near 25° lat. to form a subtropical jet that is south of the polar jet
• It usually has _______ speeds than the polar jet

Subtropical Jet Stream

• Subtropical jet will sometimes move north far enough that it ________ with the polar jet
• In summer, ________ gradient not large enough, so subtropical jet is weak to non-existent