Miss McDonald EQ2 (ON SPEC) Flashcards
Meteorological drought
Degree dryness compared ‘normal’ precipitation
Agricultural drought
Insufficient water for crops so that they wilt without irrigation
Hydrological drought
Where drainage basins suffer shortfalls
Global atmospheric circulation
-low pressure=warm air rises+cools forming precipitation
-high pressure=cool air falls+warms surface bringing clear skies no rainfall
E.g. ‘sub tropical’ band 30degrees N/S air risen equator cooled+sinks forming belt high pressure hot,dry conditions
ITCZ
- Belt low pressure(rain) migrates W/seasons 23degrees N/S or 0- alternating wet+dry seasons
- may fail blocked high pressure from descending part Hadley(high pressure) or loops jet streams occasionally break up allowing high pressure from subtropics move N+ block bringing droughts mid latitudes (UK)
ENSO
El Niño+ La Niña(opposite) shift rainfall patterns
- El Nino brings warmer water to America’s reducing rainfall W pacific
- la Nina brings warmer water to extreme W of tropical pacific reducing rainfall W americas
Flooding UK-jet stream+ low pressure weather
As Mid latitudes=boundary zones polar+tropical air masses where jet steam formed-brings low pressure(frontal rain)by meeting warm+ cold air+uplift condensation
Sometimes high pressure blocks jet stream+ continually delivers low pressure to 1area high pressure either side
Flooding India-monsoon
Intense seasonal rainfall-widespread damaging flooding
Around 70%annual avg rain 100days July-Sept, 80%Bangladeshi ppl affected, 1/2 country less 12m above sea lvl, low-lying plains largest rivers most at risk along river courses+at edge delta
Flooding Siberia-Ice melt
- Siberian snow melt spring causes extensive flooding across interiors Asia e.g. River Ob
- Quick transition winter-spring upstream causes rapid snow melting while lower reaches remain frozen W/v limited infiltration
- Flood water often held up temp ice dams
- Sometimes rain falls melting snow when rapid thaw occurs-> this combo can cause heavy flooding
Physical primary meteorological causes Cumbria floods 2015
- flooding happened 3rd time 2015 in a decade 2005,2009+2nd wettest nov since 1910
- moist air mass stayed over Cumbria up to 48hrs delivering records amount rain
- jet stream remained over N longer usual normally moves N+S brought low pressure (rain) from across Atlantic thru ‘conveyor’ warm+v moist air from Caribbean where sea temps unusually high
- Cumbria= wettest seathwaite avg 2mrainfall/yr
Secondary causes for Cumbria floods 2015
- steep slopes Cumbria Mountains helped steer run rapidly into river (orographic rainfall)
- ground already saturated from previous antecedent conditions meant additional rain flowed surface run-off straight into rivers
- rivers Derwent+Cocker= already swollen W/ previous rainfall
- impermeable rock type Lake District impeded infiltration
- Cockermouth built confluence 2rivers making susceptible flooding after heavy rains
Soc impacts Cumbria floods 2015
- 3000homes flooded 2005+5,200 2015
- 40skls closed
- routine business across NHS hospitals cancelled
Econ impacts Cumbria floods
- UK dented as much £3bn damage storms Eva, Desmond+ Frank
- insurance claims caused flooding 2015 exceeded £6bn
- house prices fell flood-risk areas
Environ impacts Cumbria floods
- river chocked W/debris+contaminated sewage+ effluents+ pollutants
- saturated ground-decomposition dead plants+animals giving off noxious gases- contaminated food chains+threatened wild life
- soils=eroded habitats destroyed+ecosystems destroyed
How climate change might affect drainage basin if drier than normal
- Decreases precipitation 10-30degrees N+S equator(inputs)
- initial high rates evaporation followed lower lvls when available water falls+EVT decrease as less soil moisture affecting veg as outputs
- reduce lvl water stored soil, rivers+lakes causing increased reliance+use groundwater W/more humidity+ increased drought severity+freq
- Increasing high pressure zones e.g. subtropics+ drier soils altho more intense rainfall events