L. 3: Why climate change will affect hydrology, C. 2-Barnett Flashcards
Precipitation models
Much disagreement; balance of hydrological cycle is not zero as should be. Clouds not in models.
Warming in atmosphere
Evaporates more water; can hold more moisture; more clouds. Cycles speed up – goes up faster and comes down faster. Water is how energy is transported around globe; there is more energy in atmosphere because of warmer temperature and trapping of rays. Heavier rainfall events because more water in atmosphere, and though cooler areas need larger vertical movement of water, in future will need less because so much already.
Where movement is up, rainfall increases.
Poleward expansion of Hadley cell, more warming at poles and less sea ice covering, so more ocean evaporation. Poles get wetter.
Seasonal changes
Warmer temperatures will increase snow melt in glaciers, changing time of peak flow to earlier in spring/ end of winter. Means drier conditions during driest/warmest time of year; more flooding in winter and spring.
albedo
Loss of glaciers will decrease albedo, warm land more, but Asian monsoons weakening.
Impact on/of plants
More CO2 means photosynthesis increases, but plants will close stomata and use less water for food, so more runoff. Plants are more efficient. Deforestation decreases precipitation.
Snowpack
Decreasing. In US last 100 years, 56% of glacier coverage gone. Tree rings show some of smallest glaciers in 800 years. Snowmelt earlier, runoff earlier.
El Nino and La Nina
Hadley cells moving a degree latitude per decade, pushing rainfall further north, out of SW U.S. Strong El Nino means wet in SW, but La Nina more drying in SW U.S. Pacific will grow into more consistent La Nina conditions (means high pressure system further into north pushes polar jet stream north and pacific jet stream north over northwest Pacific ocean). Protracted La Nina, global cooling, stronger trade winds push warm water farther west, SW drought. Rich get richer, poor (water-stressed areas) get poorer.
Evaporation in global warming
Increases, NE getting wetter when precipitation and stream flow averaged over year, but more extreme events, more intensity, more rain, soil moisture dryer because warming makes drier and increases evaporation.
Barnett- Impact of warming climate on water availability in snow-dominated regions
1/6 of world population lives in areas where water supply is mostly runoff from melting snow or ice (generally regions in latitudes greater than 45 degrees). Shifts in timing of runoff will affect dry season water availability. Global warming decreases amount of precipitation falling as snow, causes runoff from melting snow and ice to occur earlier in winter and spring. Less storage of water in form of snow/ice for summer supply when demand is greatest. Projections based on temperature models (not precipitation models, which have not included effects of aerosols including clouds).
