HW3-solution - HOMEWORK 1 (DUE 03/08 @ 5 pm at TAs office)...

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HOMEWORK 1 (DUE 03/08 @ 5 pm at TA’s office) Total Points: 144 1. Describe the air flow patterns of the 3-zone Hadley cells. Then explain why the trade winds in the northern hemisphere are northeast while in the middle latitude (30 – 60 o ) the winds are southwest. (12%) Hot (less dense low pressure) air rises from near the equator, where it is consistently heated by the sun. It rises and then disperses, heading both north and south. Focusing on the northern hemisphere, the hot air from the equator slowly cools as it travels north at a high altitude, until it becomes heavy enough (denser high pressure) to sink back to the earth’s surface. This generally occurs at approximately 30 o latitude (Subtropical High). Once the air returns to the earth’s surface, it once again disperses north and south. The air stream that heads south returns to the equator, where the system is initiated once again by equatorial warming. That system comprises the official Hadley cell. At the North Pole, the air becomes very cold and more dense (high pressure), which causes the air current to fall to the earth’s surface in a type of Hadley circulation pattern. From there, it travels southerly along the earth’s surface until it reaches about 60 o N latitude, where it is sufficiently heated and becomes less dense (low pressure), and the current begins to rise. Once again, it disperses north and south, with the air current that returns to the north once again cooling and re-initiating what is officially known as the Polar circulation cell. The Ferrell cell operates between the Hadley and Polar circulation cells. Its motion is more complex than that of the other two circulation cells, and it is dependent on the other two more stable cells. There is no direct thermal means to drive the circulation, which is the case in the other two (equatorial heating for the Hadley cell and polar cooling for the Polar cell). The general means of motion for the Ferrell cell is the movement of some of the cooled air at 30 o N (for the northern hemisphere) from the Hadley cell moving northwards as it disperses at the earth’s surface. Similarly, some of the rising warmer air at the southern end of the Polar cell at about 60 o N (for the northern hemisphere) will circulate southwards into the Ferrell cell at high altitudes. This forms the general motion of the Ferrell cell in the northern hemisphere, high pressure near 30 o N and lower pressure near 60 o N, causing the wind on the earth surface to move from the south to the north. The trade winds in the northern hemisphere are northeast because of the return of the
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HW3-solution - HOMEWORK 1 (DUE 03/08 @ 5 pm at TAs office)...

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