BOW ECHO
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A Bow Echo is a radar signature of a severe thunderstorm that has a characteristic bow-shaped (arc-like) appearance. It typically indicates strong straight-line winds and is often associated with damaging windstorms, known as derechos
A bow echo refers to a line of thunderstorms, also known as a squall line, that appears bow-shaped on radar. At times, this bow echo may be part of a larger squall line system. It typically spans a distance of 20 to 100 kilometers and can persist for three to six hours. The term "bow echo" was first introduced in the 1970s by Ted Fujita, a renowned Japanese-American meteorologist who also created the tornado classification scale known as the Fujita Scale
- When cool air from rainfall descends and spreads across the ground, it creates a boundary known as the gust front, which separates the cooler air from the warm, moist air at the surface. This boundary forces the warm air to rise into the atmosphere, triggering the formation of new thunderstorms.
- These fresh storms bring more rainfall, producing additional cool air, which helps reinforce the gust front. As this cycle continues, the airflow begins to enter from the rear of the storm line, causing it to curve into a bow-like shape, similar to an archer’s bow. The process sustains itself as long as new thunderstorms form ahead of the system, allowing it to intensify and advance with strong winds
4. Effects of bow echo
- Damaging Straight-Line Winds Bow echoes produce severe straight-line winds that can cause major damage, with an axis of enhanced winds that spread horizontally and repeatedly enforce the bowing structure.Wind speeds can reach extreme levels, with 100+ mph winds reported in severe cases
- Downbursts and Microbursts All along the leading edge of bow echoes, thunderstorms may produce downbursts and microbursts
- Macroburst and microburst winds are common with these storms creating concentrated areas of extremely damaging winds that hit the ground and spread outward
- Brief Tornado Formation Bow echoes can occasionally produce tornadoesthough these are typically brief and weaker than supercell tornadoes. Weak to occasionally strong tornadoes may occurespecially near the bookend vortices at the ends of the bow structure.
- Surface Wind Damage The straight-line winds create distinctive damage patterns different from tornadoes:
- Trees blown down in the same direction rather than twisted
- Structural damage to buildings from sustained high winds
- Power line failures creating widespread outages
- Agricultural crop damage over large areas
5. Way forward
Bow echoes are not a recent occurrence. For instance, on May 31, 2022, one developed over Delhi and Noida, although it lasted only about an hour and generated wind speeds reaching 100 km/h. A similar squall line was also noted during thunderstorm activity in Odisha earlier this month
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For Prelims: Flash floods, bow echo, Thunderstorms.
For Mains: 1. Analyze the major challenges and threats faced by the Yamuna River, including pollution, encroachments, and over-extraction of water. (250 words).
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Previous year questions1. Consider the following tributaries of River Yamuna and arrange them from West to East : (UPSC 2020)
1. Betwa
2. Ken
3. Sindh
4. Chambal
Select the correct answer from the codes given below.
A. 4, 3, 1 and 2
B. 1, 2, 3 and 4
C. 3, 2, 1 and 4
D. 2, 3, 1 and 4
Answer: A
2. Consider the following pairs: (UPSC 2019)
Glacier River
1. Bandarpunch Yamuna
2. Bara Shigri Chenab
3. Milam Mandakini
4. Siachen Nubra
5. Zemu Manas
Which of the pairs given above are correctly matched?
A. 1, 2 and 4
B. 1, 3 and 4
C. 2 and 5
D. 3 and 5
Answer: A
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