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Global weather (Tropical cyclone (Formation of TC: (No cyclogenesis near…
Global weather
Tropical cyclone
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Tropical storm= convection concentrated in centre, 34kts < v10m < 63kts
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Formation of TC:
No cyclogenesis near equator, two thirds form between 10° - 20° N or S
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Impacts
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Can cause large impacts: 300,000 deaths in Bangladesh during Tropical cyclone Bhola in 1970
Polar jetstream
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Jetstream= a region of high speed winds in upper troposphere, stretching around the globe
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Polar jetstream in upper troposphere is caused by strong temp gradient between polar and subtropical air
Hurricane structure
Eye wall: deep convection, 10-20km wide, strongest wind and rainfall
Required centripetal acceleration is provided by imbalance between pressure and orioles force, providing gradient wind
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Enormous pressure gradients are needed to balance high winds in TCs, category 5 hurricanes can reach pressures <900hPa
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Wind speed decreases with height, contrasts with mid lat cyclones
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Hadley circulation
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Ferrel cell is particularly changeable, polar front between polar and ferrel cells can vary from 40⁰ -75⁰ N