Transcript PP-Intro (NXPowerLite)

Geography 311 – Climatology
Geography Major
Global Environmental Change Cluster
Questions to think about:
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What is climate?
How is climate different from weather?
Are they related?
What controls the climate?
Does climate change – do we care?
Can climate be predicted?
Why is it so darn wet?
Why is central Europe (or Wisconsin) flooding?
Weather and Climate
Meteorology and Climatology
Elements
&
Controls
Elements
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Temperature
Precipitation
Solar Radiation
Wind Speed and Direction
Atmospheric Pressure
Humidity
Visibility
Climate Controls
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Latitude
 Earth-Sun
Relationships
 Major pressure and wind systems
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Marine vs. Continental Setting
 Proximity
 Relative
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to prevailing winds
Topography
 Elevation:
normal lapse rate
 Topographic barriers
Do you want to be a Meteorologist
or a Climatologist ??
Meteorology
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Physics and Math
Current state of the
atmosphere – and short-term
future
Data-collection via
radiosondes and satellites
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Solve equations of motion
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Be a TV Star like Matt - KGW
Tools of the Meteorologist
Radiosonde….
Do you want to be a Meteorologist
or a Climatologist ??
Climatology
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Geography and
Environmental Sciences
Long-term state of the
atmosphere – averages and
measures of variability
Data-collection: Cooperative
climatological network
Statistical analysis and
mapping
Impacts on human activity
Be a College Prof like Dan
Climate Regions
Isotherms - temperature
Annual Precipitation
Long-term Trends
Government Agencies
Meteorology: National Weather Service
Mission: Protect Human Life and Property
Portland Weather Service Office
Seattle Weather Service Office
Datastreme – 0nline Meteorology Course
Unisys Weather Page
Climatology: National Climate Data Center (NOAA)
Mission: Archive and provide historical data
Western Regional Climate Center
Oregon Climate Service
(Note: First Web Assignment)
A Few Basics:
Planetary Energy Balance
Energy In = Energy Out
S (1   ) R  4 R  T
2
2
4
T  18o C
But the observed Ts is about 15° C
(Ts – surface temperature)
What’s Missing?
Vertical structure of the Atmosphere and the
composition of the atmosphere.
The “greenhouse effect”
Energy storage and transport
The “general circulation” of the atmosphere and
oceans
Hence: The Climate System
The General
Circulation
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Solar heating is greater than longwave cooling in the tropics: energy
accumulates there, both in the atmosphere and the oceans
Longwave cooling is greater than solar heating near the poles: energy is lost
there, by thermal radiation to outer space
The “job” of the atmosphere and the oceans is to transport energy from where
it accumulates to where it can be lost
(poleward and upward)
This job is difficult because of the Coriolis force – yet it is Coriolis that turns
North/South (meridional) transport into East/West (Zonal) winds.
How is Energy Transported
to its “escape zones?”
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Both atmospheric and ocean transport are crucial
Buoyancy-driven convection drives vertical transport
Latent heat is at least as important as sensible heat
Atmospheric Circulation
in a nutshell
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Hot air rises (rains a lot) in the
tropics
Air cools and sinks in the
subtropics (deserts)
Poleward-flow is deflected by the
Coriolis force into westerly jet
streams in the temperate zone
Jet streams are unstable to small
perturbations, leading to huge
eddies (storms and fronts) that
finish the job
Ocean Currents
midlatitude “gyres”
W-E flow in tropics
circumpolar current
How are these known? Effects on poleward energy transport?
Climate vs. Weather
(as related to predictability)
“Climate is what you expect
… weather is what you get!”
Climate is an “envelope of possibilities” within which
the weather bounces around.
Climate is determined by the properties of the Earth
system itself (the boundary conditions), whereas
weather depends very sensitively on the evolution
of the system from one moment to the next.
Predictability
“If they can’t predict the weather, how can they possibly hope to
predict the climate?”
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Weather forecasts are only useful for a few days,
maybe a week at best
Forecasting is limited by modeling skill and
inadequate observations, but even if these were
perfect, the limit of predictability would be about 2
weeks
This limit is a property of the atmosphere itself, not a
failure of our science!
Give the weather folks a break!
Limits to Predictability
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The dynamical equations governing the motions of the
atmosphere and oceans are strongly nonlinear.
This makes them very sensitively dependent on their
initial conditions.
Errors in the initial conditions, no matter how trivial or
on how small a spatial scale, quickly grow in magnitude
and propagate to larger spatial scales.
Butterfly analogy of Lorenz (1963):
Predictability Times
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Boundary-layer eddy:
Cumulonimbus clouds:
Mid-latitude cyclone:
Big standing waves:
El Niño:
Deep ocean circulation:
10 minutes
1 hour
3 days
10 days
100 days
50 years(?)
Forecasting (time-frames)
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Can’t forecast the weather in Portland on the day of the Geog 311
final exam in December:
(Snow? Sunshine? -10 C? +20 C?)
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Can we forecast that tomorrow will be colder than it is today?
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Can “forecast” with complete confidence that –100 C < Tmax < +100 C
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Why?
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Boundary conditions – aka External Controls!
 Solar constant
 Atmospheric composition
 Tilt of Earth’s axis, latitude, etc
Slow vs. Fast Climate Components
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Some parts of the Earth system are slower to respond to
changes than the atmosphere (e.g., ocean temperatures,
soil moisture).
Such slow processes give the climate “memory”.
If processes that control these “slow” processes are
known, they may be predicted.
The statistics of the weather respond in systematic and
predictable ways to changes in boundary forcing.
Boston (45 N. )
Zimbabwe (20 S.)
Seasonal Forecasting
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In the past 10 years, we’ve learned a lot about the processes that
control tropical Pacific sea-surface temperatures (El Niño and La
Niña).
Once these processes get started, we can predict their evolution
with some skill.
Weather anomalies associated with these events are then
forecast several months in advance.
Works much better in some places than others (not too reliable
at Fort Collins, Colorado; but more so in Portland, Oregon).
Why?
Climate Modeling
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Weather and ocean circulation are governed by a set of reasonably
well-known deterministic equations (like F = ma).
The governing equations of climate are in general not known.
Climate modeling is for the most part a “brute force” activity that
involves running “weather” forecast models for a very long time
with perturbed or slowly changing boundary conditions.
The initial conditions of a climate simulation are forgotten in a few
simulated weeks.
The statistics of the simulated weather are the output of interest, the
simulated climate.
Examples of Climate Simulations
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Ice-Age simulations require only a knowledge of boundary
conditions:
 Orbital geometry
 Sea-surface temperatures
 Ice orography
The atmosphere quickly adjusts to the changed conditions, and an
ice-age climate develops.
Simulations of global warming involve perturbed boundary
conditions too (atmospheric composition and radiative properties).
Ocean response is critical, and must be predicted, not prescribed.
GUIDING PRINCIPLE FOR INFORMED CLIMATE
DECISION:
Humans can take actions to reduce climate change and its impacts.
CLIMATE LITERACY: The Essential Principles of Climate
Science
• The Sun is the primary source of energy for Earths climate system.
• Climate is regulated by complex interactions among components of the
Earth system.
• Life on Earth depends on, is shaped by, and affects climate.
• Climate varies over space and time through both natural and man-made
processes.
• Our understanding of the climate system is improved through
observations, theoretical studies, and modeling.
• Human activities are impacting the climate system.
• Climate change will have consequences for the Earth system and human
lives.