[Geography Notes] on Subtropical Jet Stream Pdf for Exam

In Geography, jet streams are defined as the fast-flowing air currents characterized by their narrow and meandering type current. The jet stream is prevalent in some planets including our planet Earth.

On Earth, main jet streams are located near the altitude of the tropopause region and are located in the western winds which are flowing west to east. The path of this wind has a typical meandering shape. Jet streams can start, stop, split into two, or can have more parts. While, at last, they combine into one single stream. 

On the same subject matter, we will present our discussion in an elaborate fashion.  

Subtropical Jet Stream 

The Subtropical jet stream is a belt of strong upper-level winds that lie above the regions of the subtropical high-pressure region. Unlike the polar front jet streams, this wind travels in the lower latitude regions and at a slightly higher elevated region, this is because of the increase in height of the tropopause layer at the lower latitudes. The temperature gradients of this jet stream do not extend to the surface area, for this reason, the surface front is not evident. While in the tropical region an easterly jet is at times found at upper levels. Mainly this wind is found when a landmass is located poleward of an ocean, for this reason, the temperature increases with the latitude.

Subtropical Westerly Jet Stream 

The name ‘Subtropical Westerly Jet stream’ is located over 27-degree to 30-degree north latitude. In our country, the jet streams blow south of the Himalayas. This wind blows in India all through the year except in the summertime. The north and the north-western parts of the country experience western cyclonic disturbances, this happens for the westerly flow in the wintertime. While in summertime the subtropical westerly jet streams move northwards towards the Himalayas with the movement of the sun.   

The Western disturbances abbreviated as WDS are the mid-tropospheric to upper‐tropospheric mesoscale vortices. They typically propagate along with the subtropical westerly jet stream. This brings heavy rainfall in the country, Pakistan, and in northern India during the boreal winter.

They act similarly to the Tibetan Plateau vortices (TPVs). This wind also affects southwest China during the springtime and in the summer season. This wind originates from the Tibetan Plateau. 

The similarity implies the existence of a general group of upper‐tropospheric vortices that features interactions with the orography of the Hindu Kush‐Himalaya‐Tibetan Plateau region.

Equatorial Jet Stream

The Jet streams are the narrow bands of strong and gusty winds blowing in the upper levels of the atmosphere. Normally the jet streams blow from east to west, but at times it often shifts to north and south as well. Like any other winds, the jet streams follow the boundaries between the hot and cold air. The cold and hot boundaries are characterized in the wintertime. The jet streams are the strongest in both the northern and the southern hemisphere. 

The Daunting Question is, why does the Wind Blow from West to East?

To recollect from our previous study, if the earth did not rotate, the global winds, the warm air at the equator would drift towards both the polar regions. Hence, we see that the earth’s rotation has divided the wind circulation into three cells. The rotation of the planet is also responsible for the cause of jet streams. 

When the wind moves away from the equatorial region, the motion of the air is not directed towards north and south but it is affected by the momentum as it drifts away from the equator. This is reasoned out for the momentum of how fast a location present on or above the earth moves relative to the earth’s axis. 

Your location will determine the speed relative to the earth’s axis. If you stand on the equator, and your friend is standing on a 45-degree latitude line, you will find miraculously that you move faster than your friend. While another friend, suppose standing on the pole will not move at all. While he or she will only spin standing on the pole. This speed of rotation is great enough to lower the weight up to one pound if standing on the pole than on the equator.   

What Causes Jet Stream?

We need to understand this fact, that the Sun doesn’t heat the entire earth evenly, at some places it heats more like in the equator, the sun is unbearable. While, at some places, the sun rays may not reach properly, like in the polar regions. For this very reason, the areas near the equator are quite hot and the areas near the poles are very cold.

So, when the Earth’s warmer air masses meet or collide with the cooler air masses, the warmer air rises higher in the atmosphere while the cooler air sinks to replace the warm air which rose above. This movement creates an air current, or wind to gush down. This forms the jet stream. 

On Our Planet, There are Four Jet Streams. 

The Jet streams are formed in the atmosphere when the warm air masses meet the cool air masses. 

On average, jet streams blow at about 110 miles per hour, calculated approximately. The temperature difference between warm and cold air masses is quite dramatic then it will cause the jet streams to move speedier, which can be 250 miles per hour.