Question

4) Jet Streams and Global Change a Esai camatc hecation of isitubejt aby examining surface temperatures across North America. b) Why are the midlatitude jet streams stronger in the wintertime than in the summertime? c) How would an increase in Earth's obliquity change the wintertime jet streams? d) For a global warming scenario, in which polar ice is completely melted, describe how you would expect the Jet Streams to be different.

Answer 1

4.a. As we know the jet streams 'follow the sun'. What this means is that as the sun's elevation changes with the seasons the boundary between cold and warm air masses also shifts and this causes the jet stream to shift. The approximate location of the midlatitude jet stream can be found by examining the surface temperatures across North America. The mid-latitudinal jet stream will be mostly at the location where the sun's elevation is close to 90 degrees i.e. sun is in an overhead position. This is supported by the fact that as spring season comes forth in the northern hemisphere the mid-latitudinal jet stream moves towards the north i.e. towards the poles.

b. The mid-latitudinal jet stream is formed when the warm front of Hadley cell interacts with the cold front of the Ferrel cell. In winter season the temperature differential between the warm air mass of the Hadley cell and the cold air mass of the Ferrel cell gets pronounced which leads to a stronger mid-latitudinal jet stream in winters as compared to the summers.

c. An increase in earth's obliquity would lead to colder winters and warmer summers on the earth. So in wintertime, this would lead to the Polar cell and Ferrel cell getting extended to further south than their present extents in the northern hemisphere. This, in turn, would lead to the formation of the Polar jet stream and mid-latitudinal jet stream at much southern latitudes i.e. much closer to the equator, in the northern hemisphere.

d. In a global warming scenario where the polar ice has completely melted, we would no longer have the great heat sink at the poles which drive the polar cells. Due to this, the polar cells would weaken considerably or may even cease to exist. Due to this, we may not have a polar jet stream anymore and only a mid-latitudinal jet stream may remain in either hemisphere.