Lecture Oct 18

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Lecture Oct 18
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Todays lecture

• Quiz returned on Monday
• See Lis if you didnt get yours
• Quiz average 7.5 STD 2
• Review from Monday
• Calculate speed of air moved from equator to 30
  North
• How Satellites view Earth
• Wavelengths and Atmospheric Window

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Tropics have a surplus of energy and the poles a
deficit. A net poleward transport of energy is
therefore required.
ENERGY
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Winds Patterns Balance of 3 forces

• The pressure gradient force causes wind to blow
  from high pressure toward low pressure.
• The coriolis force causes wind to be deflected to
  the right of the motion in the northern
  hemisphere.
• Friction which slows the wind.

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http//teacherresourceexchange.org/science/corioli
s/index.php
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The poleward transport of energy occurs in the
fronts and low pressure systems of the middle
latitudes.
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Water Vapor Transport Pathway
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Satellite image of the United States
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As light travels through our universe wavelengths
of light stretch!
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Wavelengths of Light
Radio Microwaves Infrared Red Orange Yellow Green
Blue Violet Ultraviolet X Rays Gamma Rays
There Are Many Colors We Cant See!
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Light emitted by the Sun
Wavelength of Peak emission 2898 microns /
Temperature of Blackbody (K).
http//feps.as.arizona.edu/outreach/bbplot.html
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Emission by the Earth (288K)
http//www.utsc.utoronto.ca/shaver/blackbody.jpg
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http//ceos.cnes.fr8100/cdrom-00b/ceos1/science/d
g/dg9.htm
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Visible Light
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Infrared Light
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How much of the Earths Energy is absorbed by our
atmosphere?
Visible- Satellite images in the visible band are
from reflected sunlight
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How do meteorologists predict the weather?
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Computer Models
Weather and climate prediction require models of
the earth-atmosphere system.
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Computer Models

• A model is a computer program that represents the
  predictive equations that describe weather
  variables.
• What does a weather model look like?
  www.weather.unisys.com
• What variables do they describe?

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Computer Models
Equations can predict because- they describe the
change in time of a variable. These equations do
this in terms of the forces involved that may
change the variable and the advection of
different properties by the wind.
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Advection

• Wind is bringing in warmer temps

WARM AIR
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Computer Models
Weather and Climate models use horizontal and
vertical grids. The equations are solved at each
grid intersection.
http//www.research.noaa.gov/climate/images/modeli
ng_schematic.gif
http//climateprediction.net/images/sci_images/ver
ticalres.jpg
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Computer Models

• Horizontal grid spacing for weather forecast
  models is quite variable but ranges between 10-50
  km. Weather forecast models typically have 20-50
  vertical levels.
• Climate models have much coarser grids with
  horizontal spacing of hundreds of km and just
  10-20 vertical levels.

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Weather and Climate models are different from one
another in other ways 1. The goals of the
prediction are different. Weather forecasts
need to be accurate in an absolute sense I.e.
yes it will rain tomorrow. Climate predictions
usually are trying to determine change I. e.
the climate will warm 2 degrees. (Show
calculations)
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• Weather and Climate models are different from one
  another in other ways
• What weather models can assume unimportant is
  often quite important for climate models.
• The ocean temperature, for instance can assume
  to be constant for weather prediction but becomes
  very important to climate predictions.

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Meteo 1020 Lecture 3 Weather and Climate
The coarse grid of climate models requires that
many physical processes important to climate must
be represented approximately (parameterized).
An example would be a thunderstorm system that
is 50 km wide. A weather model could predict this
accurately with a 10 km horizontal grid. For a
climate model with a 200 km grid, this
thunderstorm exists at a scale too small to
resolve and its affects will not be represented
unless a parameterization is developed to
approximate it. Poorly developed
parameterizations are THE LEADING CAUSE of
climate model error!
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Meteo 1020 Lecture 3 Weather and Climate
Model error (both climate and weather prediction)
also arise from other sources 1. Poor initial
conditions this is often due to bad data.
Consider the importance of far off observations
to the 7 day forecasts given that weather
disturbances can travel hundreds of kilometers in
day! 2. Predictability due to nonlinearity
(advection of the wind by the wind), our ability
to predict the atmosphere, even with perfect
observations, is limited. A certain amount of
Chaos exists in the system that effectively
limits absolute predictions of the atmospheric
state.
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Meteo 1020 Lecture 3 Weather and Climate

• The hydrologic cycle refers to the set of
  physical processes that redistribute water in its
  three phases (gas, liquid, and solid) within the
  earth system.
• The following three points are quite important
• Understanding the hydrologic cycle is of utmost
  importance in understanding climate!
• Recall the primary greenhouse gas is NOT carbon
  dioxide but water vapor!
• The parameterization errors that lead to
  uncertain climate predictions are primarily due
  to many of the physical process that compose the
  hydrologic cycle.

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Meteo 1020 Lecture 3 Weather and Climate

• The law of conservation of mass applied to water
  in the earth system- For most purposes the mass
  of water is fixed so the rate of change of total
  water mass is zero.
• With this understanding, we can write a
  predictive equation that tracks water through its
  various phases in terms of sources, sinks and
  storage.
• The physical processes surrounding the phase
  changes of water are key to understanding the
  hydrologic cycle
• Saturation vapor pressure is a strong function of
  temperature
• Increasing energy is required for a water
  molecule to move from solid to liquid to gas.

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Meteo 1020 Lecture 3 Weather and Climate

• Conservation of energy applies The energy
  required to evaporate a water molecule is
  released as heat when the molecule condenses.
• This source of heat (the latent heat of
  condensation) is a critical energy source for the
  atmosphere.
• Latent heat drives thunderstorms development
• energy in the form of latent heat is
  transported from the tropical oceans to the
  higher latitudes on air currents. The energy is
  released when the water condenses to form clouds
  and precipitation.
• The image on the following page illustrates the
  poleward transport of water vapor. The white
  areas are clouds while the gray areas are
  composed primarily of upper tropospheric water
  vapor

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Sunlight that Enters our Atmosphere
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Weather vs. Climate

• Climate
• Time Average
• Variance
• Defined by the extremes of weather
• Used to describe how the system works on long
  time frames

• Weather
• Characterized by change
• Time Scale-
• Hour to hour
• Day to night
• Month to Month

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Weather vs. Climate

• Weather
• Time Scale-
• Hour to hour
• Day to night
• Month to Month