28/10/2024
✦ Jet Stream: A jet stream is a fast, narrow air current flowing from west to east, circling the Earth in both hemispheres at altitudes between 8 and 15 km, typically centered around the tropopause within latitudes of 10 to 60 degrees. According to the World Meteorological Organization (WMO), the jet stream is a powerful, narrow funnel-shaped air current. WMO defines it as: “The jet stream is a strong narrow current concentrated along a quasi-horizontal axis in the upper troposphere or in the stratosphere characterized by strong vertical and lateral wind shears and featuring one or more velocity maxima.” The jet stream flows counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
✦ Identification of the Jet Stream: The jet stream was first identified by Japanese meteorologist Wasaburo Ooishi at the "Upper-air Observatory at Tateno" in Japan in the early 1920s. He observed it in the upper atmosphere near Mount Fuji and presented detailed information in his 1926 report "Raporto de la Aerologia Observatorio de Tateno" to the Aerological Observatory of Japan. However, due to language barriers, this information remained within Japan. A few years later, in July 1933, American aviator Wiley Hardeman Post rediscovered the jet stream while observing Earth’s atmosphere from the stratosphere using his Solo balloon, bringing this phenomenon to the attention of the global community. The jet stream’s existence became more widely understood during World War II.
✦ Naming: Although the jet stream was discovered separately in Japan and the United States, it was not formally named. In 1939, German meteorologist Heinrich Seilkopf referred to this airflow as "Strahlstromung" (literally "Jet Flow") in his "Handbook of Aeronautical Meteorology." He described it in detail on pages 142 to 150. Later, in 1947, Swedish meteorologist Carl-Gustaf Rossby referred to it as the "Jet Stream" in an article titled "On the distribution of angular velocity in gaseous envelopes under the influence of large-scale horizontal mixing processes" published in the "Staff Members" research journal by the meteorology department at the University of Chicago.
✦ Characteristics of the Jet Stream: The jet stream is a powerful air current encircling Earth in the upper atmosphere with the following key characteristics:
- i. It flows at an altitude of around 8 to 15 km, resembling a winding, spiral river.
- ii. The jet stream has high-speed air currents, ranging from 322 to 483 km/h, with maximum speeds at 9-12 km altitude.
- iii. It combines strong vertical and horizontal wind currents, with vertical winds averaging 5-10 meters per km and horizontal winds at 5 meters per 100 km.
- iv. The jet stream typically resides between 30 and 40 degrees latitude, although it can be found between 10 and 60 degrees latitude. It is colder toward the poles and warmer toward the equator.
- v. The jet stream follows a specific life cycle with four stages.
- vi. Although it flows west to east, it bends north and south, with maximum bends to the north. Its position shifts with seasonal changes.
- vii. The jet stream spans thousands of kilometers in length, 100-150 km in width, and is several kilometers deep.
