Tropical Cyclones AICE MARINE SCIENCE AS LEVEL 2015

Tropical Cyclones AICE MARINE SCIENCE AS LEVEL 2015 -2016

Normal Wind Pattern

El Nino (southern oscillation) �sequence of events occurring in southern Pacific Ocean �Normal conditions cold nutrient-rich water flows North along west coast of S. America. Upwelling of nutrients due to winds from the South plankton-rich water High productivity � large numbers of: Anchovies Sardines � Supports: substantial fisheries industry various sea bird species

Normal vs. El Nino

El Nino Conditions �Every ~7 -10 years Winds stop blowing from East or SE Warm equatorial water is blown by abnormal winds from the West. Pressure gradients in East and West Pacific are reversed � Reverse in wind direction and equatorial currents � Large area of warm water forms = cold-water species death � Upwelling stops � Nutrient supply to surface is reduced = lack of nutrients = primary production rapidly decreases Affects higher trophic levels Collapse of commercial fish stocks

El Nino Example �Major event in 1982 -83 Surface temps decreased by 5⁰C Heavy rain in normally dry eastern Pacific �Cause not known: possibly global warming? http: //player. discoveryeducati on. com/index. cfm? guid. Asset. Id =174 A 7 F 2 E-4 CF 4 -4704 -AF 3 B 1566 A 0 F 0 A 744&bln. From. Searc h=1&productcode=US

Monsoons �Asia = largest continent Climate swing: hot/wet to cold/dry �Monsoon (rainy season) - seasonal shift in wind of the Indian Ocean �Land absorbs heat faster than sea, so it heats up faster In winter, sea is warmed but not land � Warm air over sea rises and is less dense � Draws in cooler northeasterly air from land India: occurs during post-monsoon season: October - December

Monsoon �Summer (May-August) = land quickly heats and there is big temp. difference between Central Asia and Indian Ocean Land air warms, is less dense, rises Saturated air (water vapor) from southwest over Indian Ocean � Thunderstorms � Very heavy rain (80% of India’s annual) �September, land mass cools, monsoon weakens & replaced with a dry, northeast postmonsoon

Tropical Cyclone �Large mass of warm, humid, rotating air �Thunderstorms, strong winds, & rain centered around a Low Pressure �AKA: Tropical depressions, Tropical storms, Hurricanes, & Typhoons HOW TROPICAL CYCLONES FORM

Conditions Needed �Warm water, @ least 26. 5 OC (79. 7 OF) �Low Pressure �Evaporation tropical air rises & expands cools until unable retain the moisture precipitation �When water vapor rises, it condenses & releases large amounts of heat energy, increasing evaporation & driving the development of the cyclone

Rotation & Movement �Northern Hemisphere: Counterclockwise rotation �Southern Hemisphere: Clockwise rotation �Due to the Coriolis Effect & the way the winds are deflected as they approach the Low pressure �Usually tropical cyclones develop near the equator & move westward & towards the poles (determined by prevailing winds)

Eye of Hurricane Wilma

What hemisphere?

Impact on Coastal Communities �High wind �Heavy rain �Tornadoes �Lightning �Storm surge

Typhoon Sanba

Hurricane Sandy

Water spouts!

Hurricane Sandy

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