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Atms Sci 3600: Climates of the World. Anthony R. Lupo. Day 1. Hydrologic Cycle Describes the movement of water and processes through the earth-climate system General outline of atmospheric water cycle. Day 1. Day 1. - PowerPoint PPT Presentation
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ATMS SCI 3600: CLIMATES OF THE WORLDAnthony R. Lupo
DAY 1Hydrologic Cycle
Describes the movement of water and processes through the earth-climate system
General outline of atmospheric water cycle
DAY 1
DAY 1
Water evaporates, forms clouds, clouds precipitate over land and water, over land we get runoff back to water sourcesand begins all over again.
Cant ignore transpiration (plants, etc.), hydrological processes underground, etc.
Residence time for water vapor ~ 8 days.
DAY 1Water Resources
97% in Oceans
Cryosphere is about 1.5% of entire water mass (frozen water)
Fresh Water: 0.09%
DAY 1In Atmos: 1/1000th of a percent
A lot of importance though
Where do we find this small percentage in the atmosphere?
DAY 1Water Vapor
Water vapor in the vertical
Since temp decreases with height (lapse rate 6.5 deg C per km, 3.8 F per 1kft)
DAY 1Therefore water vapor content decreases with height
mixing ratio drops off more dramatically with height than temperature
Above 850 mb, water content drops off rapidly
Most is contained between 1000-850 mb
DAY 1Water Content (cont)
Where is the water mass on the earth?
See handouts given in classNCAR Tech Memo- Distribution of Topographical Quantities 1995
Winter cloud cover- in mid-latitudes over the oceans (both northern and southern hemisphere)India and Sahara less cloudy regions in winter, some subtropical regions as well
DAY 1Winter cloud cover- in mid-latitudes over the oceans (both northern and southern hemisphere)
India and Sahara less cloudy regions in winter, some subtropical regions as well
DAY 1Cloudiness (cont.)
In summer, in mid-latitudes over ocean is still cloudy
In summer the cloudiness in N.H. moves slightly northward
DAY 1
July-August low cloudiness, major deserts, Saudi Arabia, Australia, Sahara
Cloud cover over land ~50%
DAY 1Page 1.40
Relative humidity with height ,averaged in latitudinal bands
Features are fairly similar in both winter and summer
Values greater than 70% represent the boundary layer, which makes sense
In the S.H. boundary layer is fairly moist from equator to pole, N.H dries out around 30 N.trade wind deserts
DAY 1Function of the land
N.H. 39 % land, and 61 % ocean
S.H. 19% land, and 81 % ocean
Big land ocean dist asymmetry
DAY 1RH x-y plots
Oceanic areas more humid, land masses are dry, except for the tropical rain forests
Siberia in the summer is relatively humid
SE US with humidity in the summer can be some of the most uncomfortable places in the world
DAY 1Figure 1.43- PW
Precipitable Water (PW)= The sum of the values of mixing ratio in a column of atmosphere
Lots of PW near the equator where it is warmest
In summer in N.H. high PW values reach the Southern US
DAY 1/2Figure 1.45
Average precipitation over all longitudes for each latitude belt
High amounts are found in the equatorial regions, where it is warmest (among other processes---ITCZ)
Secondary maximums around 30 N and 30 Smid-latitude jet streams are found here
X-Y plot is the final diagrammore handouts coming in the near future when we discuss gen circ further
DAY 2Cloud Formation
3-legged stool example
3 things to get cloud
MoistureVertical motion (lift) Cloud Condensation Nuclei (CCN)
DAY 2Natural CCN
Sea Salt, Sand/dirt, Bugs, Pollen, etc.
Anthropogenic CCN
Pollution Sources, etc.
DAY 2Cloud types
Cloudiness impacts temperature- cloudy nights warmer than clear, for example
High Clouds
Cirrus-type clouds, ice crystals
DAY 2Middle Clouds
Alto, ice crystals and supercooled droplets
Low Clouds
Main Precip producersNimbostratus (uniform sheet) vs. Cumulonimbus (convective heap)
DAY 2Precip Clouds (cont.)
In N.H. nimbostratus dominate in winter, cumulonimbus dominate in warmer seasons Nimbostratus, are uniform with a large area of weak forcing, warm frontal (stratiform) precipitation
Cumulonimbus can grow up to 60000+ feet, severe thunderstorms, heavy convective precipitation, high albedo only snow is higherclimate impacts
DAY 2Drought
Places that are typically moist, but can become dry over a long duration, 2003, 2005-2007 was a recent drought locally
1988 was a widespread drought in the US
Drought begets drought speech to the National Press Club
DAY 2
Different types of drought
Meteorological precipitation versus normal
Agricultural stress on plants
Hydrological level of the rivers and lakes
DAY 2Drought
Basic drought equation: precipitation minus evaporation
If evaporation exceeds precip for quite a time, the result is a drought
Meteorological drought compares P-E to climatology
DAY 2Palmer Index
Rates a severity for drought
Long term index (5-6 month composite) cannot tell you if you have had relief due to a month being rainy
DAY 2
For more informationwww.drought.noaa.gov/palmer.html
Also see the Drought Mitigation CenterUniversity of Nebraska-Lincolnwww.drought.unl.edu/whatis/indicies.htm
For a summer season forecast see:Global Climate Change Group (MU)http://weather.missouri.edu/gcc
DAY 2
DAY 2Last Time
Latent heat of fusion: going to solid to liquid or liquid to solid
Snow melting takes energy from atmosphere (cooling), snow on ground takes heat from atmos and surface
Freezing opposite
DAY 2General Circ and Climate
Two ideas that are closely related
General Circulation: features of the general circulation are statistical entities, long-term statistical analysis of the atmosphere (no specific time scale)
DAY 2
Gen Circ has a specific time and space scale unlike climate which is just a time
Gen Circ- large time and large space (global) scale
DAY 2Time Scales
For the most part you cannot see general circulation patterns on a weather map
Long-term for gen circ refers to:Monthly SeasonallyAnnually
These mean features can show through in as little as 15 days
DAY 2General Circulation Pattern
3 Belts
3 cell model (or 3 belts) of the earths atmosphere, Coriolis gives rise to this (earths rotation)
See figure (Draw on Board)
DAY 2Sir George Hadley
If warm air rises and cold air sinks, there has to be this rising air at the equator and sinking at the pole
Had right idea but did not to take in account earths rotation
DAY 2
Earned him the naming rights of the tropical cells (Hadley cells on diagram).
Mid-latitude cells are called the Ferrel cell, and we have the nameless Polar Cells
DAY 23 Questions to Answer
Q: What gives rise to the Gen. circ?
Q: Why westerlies in midlatitudes, why easterlies in tropics?
Answer: Temp and Momentum Transport
DAY 2Third Question
Why are these temperature and momentum transports necessary?
Good Exam Question!
We will get at this answer in the next two lectures
Good detailed answer coming up in the future
DAY 2Other Planets
Can almost see the banded structure on Earth
Not as evident as Jupiter, but banded nonetheless
If we double the rotation of earth, we would have nine bands
Jupiter is about double our rotationhence has about nine belts (cells)
DAY 2JupiterSaturn
DAY 2VenusPluto
DAY 3Features of the Gen Circ
Existing characteristics
Gen Circ Features migrate with the seasonsSystem sloshes northward during summerWell start at the equator and move to higher latitudes
DAY 3ITCZ
Inter-tropical convergence zone
Belt of low pressureRising motions
DAY 3
DAY 3Is a place where the horizontal winds are weak (Doldrums)
Rising motions give way to strong convection (thunderstorms)
Can see this in satellite images as bands of convective areas near the equator
DAY 3ITCZStarting point for the energy (temp and momentum) transport toward the North begins
ITCZ will be located as far north as the mid-latitudes in the summer (India and Florida)
Does not progress too far south of the equator due to the large amount of ocean (weak temp gradients)
Meeting ground of the two belts of the trade winds
Height of tropopause (16-17km) greatest herewarmest temps
DAY 3Subtropical Highs
Located right around 30N/S
Highs tend to be stronger over the ocean
Associated with anticyclonic and downward motion
DAY 3
DAY 3Correspond with the majority of the worlds deserts (Great Basin, Sahara, Middle East, Kalahari, Great Sandy Desert)
Circulations give rise to the trade winds (NE wind in N.H., SE wind in S.H.)
Names: Bermuda and Azores High (Atlantic), SE Pacific High
DAY 3Mid-latitudes
30N/S-60N/S
Battle zone of air masses
Winds are generally westerly aloft and at the surface
Balance between (PGF-Coriolis)We find jet streams in this region
DAY 3Jet Streams and Polar Front
Were predicted in 1910s before upper air measurements, all based on math, jet stream was discovered during WWII over the Pacific during bombing runs
Is a gen circ feature (large time and spatial scales)
DAY 3
Reflection of the polar frontboundary between low polar temps and moderate continental temps
Jet stream located above the sfc polar front in general
DAY 3Norwiegen Model
Stage 1Stage 2
DAY 3Norwiegen Model
Stage 3Stage 4
DAY 3Norwiegen Model
Stage 5Stage 6
DAY 3Jet Stream (cont.)
Jet stream and polar front are not constantjet stream is strongest off Asia (200 mph in winter)polar front has large impacts over N. America.
During winter jet is strongest
DAY 3
Jet and Polar Front are the tracks that storms take
Ridge in Jet Streamwarmer temps
Trough in Jet Streammore polar air mass
DAY 3Polar Regions
Find two low pressure regions that are located around 60N
Where cyclones go to die:
Aleutian Low Icelandic Low
old lows never die..they just fade away!
DAY 5Highlights from Last Time
Dry Subtropical Highs
Moist ITCZ, some moisture also associated with the polar front
Jet Stream around 40-50 N, westerlyPGF=Co
Jet stream has waves in it
DAY 5Jet Streams
Waves= has about 3-4 waves
Can see these waves on hemispheric plots
Resemble a clover
Once again land sea differences determine the amplitude and location of the 3-4 wave pattern
Polar front and jet streams are good boundaries of cold arctic air and warm subtropical air
DAY 5Roaring 40s
Region in the Southern Hemisphere that experiences high wind and waves and is relatively stormy
The winds and waves are high due to low frictionin S.H. the entire band of latitude from 40-50 S is devoid of land
Made early explorations tough
DAY 5Revisit the Questions for Gen Circ
Why westerlies in the mid-latitudes and easterlies in the tropics?
What gives rise to the gen circ
Because of heat and momentum transport
Why do we need temperature and momentum transport?A. On the following slides
DAY 5Why do we need heat transport
Fairly straight forward
Incoming radiation at the equator is greater than at the poles
DAY 5
Outgoing radiation at the equator is also greater than at the poles but drops off slower than incoming as you move poleward
This results in a net surplus in the tropics and a net deficit at the poles
DAY 5Why do we need heat transport
2nd Law of Thermo: need equilibrium
Therefore, we must have a net transport of heat poleward
Strength of the heat transport is proportional to the strength of the equator-pole temperature gradient
Therefore, highest in winter (see hmwk. 1)
DAY 5Part 2: Momentum Transport
A bit trickier
Dont look at the relative wind, focus on the absolute
Momentum must be conserved
DAY 5Earth is rotating as a solid body
Set up: easterlies in the tropics, westerlies in the mid-latitudes
Earth rotates from west to east
DAY 5Part 2: Momentum Transport
Easterly winds are opposite earths rotation and extract momentum from the earthmomentum rich (for atmos.)
Westerly winds work with rotation and add momentum to earths rotationmomentum poor (for atmos.)
Mid-latitudes are a sink..tropics are a sourcemust be a net transport poleward
DAY 5Climate Change and Heat Transport
Global warming is occurring
Affects the poles more than the tropics
Therefore if you heat the poles you decrease the temperature gradient
DAY 5
Weaker heat transport, weaker storms, not an increase in storm intensity that some point too
But that is all to be seen
DAY 5Climate Change and Momentum Transport
Basically global warming, or any other factor will not act to speed up the earths rotation for our purposes
Therefore, the transport of momentum will stay fairly constant
No big impact on climate change, or at least not the focus
DAY 53 processes transporting heat, momentum, and moisture
Transport by mean motions (15-20%)
Hadley cell, Ferrel Cell, and Polar Cell
Transport by Standing Eddies (15%)
DAY 5
Aleutian and Icelandic Low, Bermuda High, Monsoon
1 and 2 are Gen Circ Features (stat)
Transient Eddies (65-70%)
Day to day featuresfronts, Ls, Hs, hurricanes, etc.
DAY 53-cell diagram
Good websitehttp://www.ux1.eiu.edu/~cfjps/1400/circulation.html
Hadley Cell, higher vertical extent thermally direct (warm rising, cold sinking)
DAY 5Ferrel Cell, thermally indirect
Polar Cell, thermally direct (lowest)
In between Hadley and Ferrel= Subtropical Jet, Ferrel and Polar= Polar Jet
DAY 5Walker Circulation
Sir Gilbert Walker, 1920s Indian Monsoon Southern oscillation
ENSO roots
Only longitudinal circulation
DAY 5In general, western Pacific has higher SSTs, lower pressure and eastern Pacific is opposite
Stormy over the western Pacific basin (suck zone, net divergence aloft)
Every so often this pressure pattern reverses (El Nino), storms and SSTs slide eastward
DAY 5El Nino and its Impacts
History of El Nino known for a long time.
Life cycle (draw on board ocean atms interaction) and recurrence time 2 7 years
Good papers on the El nino (Kelsey et al. I, II links on the http://weather.missouri.edu/gcc
El Nino impacts on North America, Missouri
DAY 6
DAY 6
DAY 6
DAY 6
DAY 6Pacific Decadal Oscillation What is it?
+ (warm) phase(PDO1)-- (cool) phase (PDO2)
DAY 6Vascillation and the NAO (Luo et al. 2007)
Why does this occur? What does it mean for our weather?
DAY 7Quasi Biennial Oscillation:
As name suggests, happens every 24 28 months and is confined to the tropics (20 N 20 S).
Associated with hurricane activity more when easterly, less when westerly so hurricane season of 2005, had easterly QBO and La Nina, both favorable to hurricane activity (Lupo et al. 2008)
DAY 7Climate Diagnostics Bulletin
DAY 72005 hurricanes (28) 1933 hurricanes (21)
DAY 7Madden Julian Oscillation / Madden and Julian (1972)
A tropical oscillation in cloudiness and precipitation that occurs every 30 60 days. Also goes by the name intraseasonal oscillation.
Influences tropical storm activity (e.g. Dec tropical storms of 2003), and can influence summer precipitation in mid-west.
DAY 7Types of Ocean Currents
2 Types of Ocean Currents
1. Surface Currents--Surface Circulation
These waters make up about 10% of all the water in the ocean.
These waters are the upper 400 meters of the ocean.
DAY 7Types of Ocean Currents
2. Deep Water Currents--Thermohaline Circulation
These waters make up the other 90% of the ocean
These waters move around the ocean basins by density driven forces and gravity.
DAY 7The density difference is a function of different temperatures and salinity
These deep waters sink into the deep ocean basins at high latitudes where the temperatures are cold enough to cause the density to increase.
DAY 7Influencing Forces
1. Primary Forces--start the water moving
The primary forces are:1. Solar Heating2. Winds3. Gravity4. Coriolis (frame of reference)
DAY 72. Secondary Forces--influence where the currents flow
Surface Circulation
Solar heating causes water to expand. Near the equator the water is about 8 cm high than in middle latitudes. This cause a very slight slope and water wants to flow down the slope.
DAY 7Winds and Surface Flow
Winds blowing on the surface of the ocean push the water. Friction is the coupling between the wind and the water's surface. Westerlies and Trades most influential.
DAY 7Winds and Surface Flow
A wind blowing for 10 hours across the ocean will cause the surface waters to flow at about 2% of the wind speed.
Water will pile up in the direction the wind is blowing.
Gravity will tend to pull the water down the "hill" or pile of water against the pressure gradient.
DAY 7Coriolis and Surface Flow
But the Coriolis Force intervenes and cause the water to move to the right (in the northern hemisphere) around the mound of water.
DAY 7Gyres
These large mounds of water and the flow around them are called Gyres. The produce large circular currents in all the ocean basins.
Northern Hemisphere Gyre flows clockwise southern Hemisphere flows counterclockwise.