5.4 Flashcards
What does drought mean?
Defecit in hydrological cycle, which is a extended period of below average rainfall for that area
What are the 4 types of drought?
Hydrological, not enough in stores in the hydrological cycle
Meteorological, under average amount of precipitation
Agricultural, not enough for farming
Socioeconomic, not enough water for people, or can’t afford it
What are the physical short term causes of drought?
Air mass movement, this is seasonal normally E.g. jetstream in summer 2018
Reduced soil moisture, water budget, seasons
What are the natural medium term causes of drought?
ENSO cycle E.g. El Nino in Australia causing very low pressure and flooding
Reduced precipitation in mountains E.g. less snowmelt means less river discharge in yukon river
What are the natural long term causes of drought?
Global atmospheric circulation E.g. Hadley and feral cell meet at tropics creating deserts
Climate change, increasing temperatures changes weather patterns and rainfall patterns
What are the cycles part of the ENSO cycle?
Walker cell
El Niño
La Niña
What is the walker cell like?
- normal conditions
- high pressure over S.America, dry and sunny
- fishermen in S.America benefit, lack of freshwater entering sea, more upwelling, more nutrients, more fish
- low pressure over Australia, rainy
- farmers in Australia benefit as there’s rain for crops
What is La Niña like?
- more intense version of walker cell
- very high pressure in S.America, very hot, droughts
- still upwelling but difficult for fishermen
- very low pressure in Australia, very rainy, floods
- farmers lose as crops destroyed
- very strong winds
What is El Niño like?
- reverse version of La Niña
- very low pressure in S.America, lots of rain, floods
- no upwelling due to lots of rain into sea, no fish, fishermen lose out
- very high pressure in Australia, no clouds or rain, hot, droughts
- farmers lose as they can’t grow crops
- opposite direction of winds
How do the ENSO cycles impact the rest of world?
Walker cell- Normal!
La Niña- cools rest of world, temp lowers 0.2°, more hurricanes in atlantic, rain in Canada
El Niño- droughts in Asia, 2014-2016, temp rises 0.2°,fewer hurricanes in Atlantic, more in Pacific
How does climate change affect the ENSO cycles?
Suggested could be stronger due to climate change, no proven evidence
What is a positive and negative feedback loop?
Positive- increase within a system, leading to instability
Negative- change reinforces a system, leading to stability
Place example of positive feedback loop
The Amazon
Temp rises-> drought increases->trees die-> less transpiration-> less conventional rainfall
What is the Pantanal wetland like?
Located in central S.America
In upper Paraguay river basin
World’s most significant freshwater ecosystem
Flooding frequent
What is a example of negative feedback loops?
Drought affected wetland
E.g. pantanal wetland
