Agenda for Lecture 9. Equatorial low-pressure trough. Primary High-Pressure and Low- Pressure Areas 9/23/2010. Continuing with Chapter 6

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1 Agenda for Lecture 9 Continuing with Chapter 6 Chapter 7 Primary High-Pressure and Low- Pressure Areas Equatorial low-pressure trough Polar high-pressure Subtropical high-pressure Subpolar low-pressure cells Equatorial low-pressure trough Inter-Tropical Convergence Zone (ITCZ) Trade winds 1

2 Polar high-pressure cells Polar easterlies Antarctic high Subtropical high-pressure cells Westerlies Bermuda high Azores high Pacific high Figure 6.14 Subpolar low-pressure cells General Atmospheric Circulation Aleutian low Icelandic low Polar front Figure

3 Upper Atmospheric Circulation Jet stream Rossby waves Jet Streams Figure 6.18 Ocean Circulation Patterns The Jet Stream and Rossby Waves Frictional drag of wind drives ocean currents. Coriolis also has an effect but not as strong. Most ocean circulation is driven by air circulating around high pressure cells Currents bring cold water from poles toward equator along west coasts andbring warm water from tropics along east coasts Ocean circulation cell called a gyre 3

4 Local Winds Ocean Circulation Land-sea breezes Mountain-valley breezes Land-Sea Breezes Land-Sea Breezes Figure 6.19 Figure

5 Mountain-valley breezes Mountain-valley breezes Mountainous terrain Many of the most productive forest ecosystems are in mountainous regions, but many methods used for monitoring ecosystem metabolism require a homogenous, flat study site Gravity driven winds contain valuable information because they collect respired CO 2 as they move down slope The carbon molecular composition of these air flows may lend insight into ecosystem metabolism in mountainous regions Study Site: overview and atmospheric sampling H.J. Andrews Experimental Forest LTER air temperature, wind speed and direction, RH, [CO 2 ], d 13 CO 2 in air 5

6 Key Results: Cold air drainage Deep well-mixed cold air drainage happens nearly every night in summer Air in canopy stratified in the day, well-mixed at night Measurements at the tower capture 30-60% of the watershed s nighttime respiration Sufficient range of [CO 2 ] for robust analysis Elevation (m) Canopy Top 19:00 20:00 21:00 Time (h) Windspeed (m s -1 ) Nocturnal air drainage offers a unique opportunity for scaling of carbon cycle processes in complex terrain using stable isotopes Measuring d 13 CO 2 of the drainage 6

7 By sampling over time (rather than height), we can collect air samples over the range of [CO 2 ] needed for good Keeling plots CO 2 (ppm) Time (h) June Sunrise 3 m 10 m m 30 m m Long-term Goals Determine sources of variation in ecosystem-respired CO 2 in cold-air drainage Invert this understanding and use CO 2 molecular composition to monitor intraand inter-annual variations in ecosystem metabolism on a basin scale Chapter 7: Water and Atmospheric Moisture Intro Unique Properties of Water Humidity Most of today s earth is covered by water (71%) 7

8 Most of our bodies are constitutes by water (~70%) Most of plants, animals, and our food are constituted by water Ocean and Freshwater Most of Distribution our bodies are constitutes by water (~70%) Unique Properties of Water the most common component has the most uncommon properties. H + O + H = H 2 O difficult to separate stable in earth s environment This molecule Is a versatile solvent Possesses extraordinary heat features (specific heat) Polarity attracts other similar molecules forming. 8

9 Unique Properties of Water Three States of Water This Polarity result in a very strong bonding: the hydrogen bonding, which explains Surface tension.e.g. insects on water Capillarity..e.g. dry paper towel Figure 7.5 Unique Properties of Water Heat Properties Phase change: Energy added or released Heat energy needed in order to affect the strong H bonding Phase Changes (Latent heat of: melting, vaporization, condensation, & freezing) Heat exchanged among phase changes of H2O provides ~30% of all E that powers Global Circulation (GC) of the Atmosphere! Figure 7.6 9

10 Humidity: water vapor in the air Relative Humidity Def.: (Relative) Humidity: (relative) water vapor holding capacity Temps %RH and changes in Evaporation, Condensation, & Temperature Dew-Point Temperature Specific Humidity Maximum Specific Humidity Saturation Evaporation = Condensation at dew point temps Figure 7.7 Actual water vapor content of the air % Relative Humidity = Maximum water vapor capacity of the air at a given temperature X 100 Humidity Dew point air is saturated when air temp=dew point temp Very cold glass of water Dew-Point Temperature: The temperature at which a given mass of air becomes saturated, holding all the water it can hold. Vapor pressure: is the air pressure exerts by the water vapor that is in the air. What about the drops on the inside of a hot, steamy cup of coffee? Specific Humidity: mass of water vapor (weight in grams) per mass of air (in kilograms) at any specific temperature. Maximum Specific Humidity: maximum mass of water vapor (g) that a kilogram of air could hold at any specified temperature 10

11 Relative Humidity: Temps & its influence on (evaporation vs condensation) Daily and seasonal relative humidity patterns High T High Evaporation > Condensation Figure 7.7 Low T Low Evaporation = Condensation Saturation Middle Clouds Altostratus Altocumulus Altostratus 11

12 Altostratus Altostratus Altocumulus accompany active, moving weather systems Altocumulus 12

13 High Clouds Cirrus Cirrostratus Cirrocumulus Cirrus generally above 16,000 feet Thin Cirrus usually not predictive, accompany all storms but may be hidden by other clouds Cirrostratus 13

14 Cirrocumulus usual significance Contrails form at -25 F or colder. Airplane engines releasing Moisture droplets Vertically developed Clouds Cumulus Cumulonimbus Small Cumulus 14

15 Small Cumulus Swelling Cumulus Swelling Cumulus Cumulonimbus 15

16 Mountain-induced Cumulus Mixed Skies Mixed Skies 16