Unformatted text preview: III. Global Distributions of III. Global Distributions of Temperature & Rainfall
A. How does the global circulation impact other parts of the Earth System?
A. B. B. Ultimate cause of the circulation is the uneven distribution of energy Temperature, precipitation, and evaporation are closely linked with the atmospheric circulation Global temperature Rainfall distribution A. A. B. Evaporation and precipitation are influenced by temperature Transport of H2O will modify the temperature distribution A. B. Impacts radiation budget (balance of the incoming and outgoing of the radiation) Creates a feedback that affects the circulation III. Global Distributions of III. Global Distributions of Temperature & Rainfall
A. LandOcean Contrasts
A. B. global temperature patterns are influenced by the distribution of land & ocean Thermal conductivity Heat capacity
A. A. B. the rate at which heat passes through material Water has a high thermal conductivity. (land has low C. A. The energy required to raise the temperature of 1g of a substance by 1*C
Water has a higher heat capacity (34 X the heat capacity of land) III. Global Distributions of III. Global Distributions of Temperature & Rainfall
a. b. c. Ocean Surface
a. Lower Albedo (absorbs more energy) Transfers heat by turbulent mixing Some energy penetrates below the surface (100 meters deep) Rapidly loses heat to atmosphere by convection and conduction Transfers heat downward by conduction Reflection and absorption only at surface
Slow process** but more rapid than warming ocean Depends on physical and chemical properties Temperature change is slow b.
a. b. Land Surface a. b. c. III. Global Distributions of III. Global Distributions of Temperature & Rainfall
a. Land/Sea Breeze III. Global Distributions of III. Global Distributions of Temperature & Rainfall
a. b. c. d. e. Seasonal variability is much greater over land surfaces than water due to different thermal properties
Greater temperature extremes over land Land is warmer in summer (cooler in winter) Greatest variability in center of continents Lowest variability in tropics Ocean provide moderating effect on coasts b. Temperature differences impact mean sea level pressure pattern
In turn impacts circulation Shift in pressure systems with season Southern hemisphere pattern is less complicated
a. b. a. b. c. c. Latitudinal variation of seasonal temperature range
a. b. Less land/water contrast Zonal flow Small range in tropics Larger range in poles a. Monsoon – a seasonal reversal of surface winds III. Global Distributions of III. Global Distributions of Temperature & Rainfall III. Global Distributions of III. Global Distributions of Temperature & Rainfall
A. Global Precipitation Patterns
A. B. Atmospheric circulation includes the transport of material as well as energy Why are water and clouds important?
Water is unique
A. B. Pollution and aerosols water B. A. B. C. D. Water, in all phases, is the primary medium energy and matter are circulated in energy system. Concentrated in reservoir A. B. C. Phase changes that occur in different locations can transfer energy from place to place Exists in all three phases at Earth’s surface Cycles easily between system components Oceans (97%) Land surface (ice, snow, lakes, rivers – 3%) Atmosphere (0.001%) iii. The Global Hydrologic Cycle III. Global Distributions of III. Global Distributions of Temperature & Rainfall iv. Precipitation and Saturation Vapor Pressure 1. 2. 3. 4. III. Global Distributions of III. Global Distributions of Temperature & Rainfall Vapor pressure: pressure exerted by water vapor in the air. Each gas exerts a pressure (Dalton’s Law) Atmosphere pressure is the sum of all partial pressure When the rate of condensation= rate of evaporation
1. 2. 5. Clouds form when the air is at the saturation vapor pressure
1. 2. Atmosphere is saturated or at equilibrium Vapor pressure= saturation vapor pressure 6. To saturate the air:
1. 2. Vapor pressure is related to dew point Saturation vapor pressure corresponds to the temperature Reduce temperature Add water vapor through evaporation (change the dew point) Partial Pressure Partial Pressure
• Recall pressure is the weight of the column of air above
– Air is 78% Nitrogen, 21% Oxygen, 04% Water Vapor 1000 mb parcel
• • • – 780 mb N2 210 mb O2 10 mb H2Ov Saturation Vapor Pressure Saturation Vapor Pressure v. Location of Deserts
1. III. Global Distributions of III. Global Distributions of Temperature & Rainfall 2. 3. Suppressed uplift and little moisture 1. Descending branch of the Hadley cell (~30°N/S subtropical highs) 2. Leeward slopes of mountains (rain shadow) Interior of land masses (no influence from ocean) West coast of large continents 1. Areas equatorward of midlat lows 2. Cold offshore ocean currents (littoral deserts (along shore))
1. 2. 3. Reduce evaporation Cool the air Inhibit convection and precipitatios ...
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- Spring '11
- A. B. C, III. Global Distributions