Lecture 19- Chapter15
1. Observation: collecting vast quantities of datathat describes the current state of the
Geostationary:orbit with the Earth thus always above the same spot, orbit height
of 36,000km above the equator. Bad views of polarregions
Polarorbiting:orbits at altitudes of only about 800km, travel along the
longitudinal lines (passes overlocations twice aday)
- good view of polarregions
Visible imagery:depicts visible light from the sun reflected by the Earth’s
surface. (like aphotograph) Disadvantageous during the day, surface with
high albedos =bright like clouds, snow and ice &, low albedos - dark like
Infrared imagery: depicts radiation at wavelengths emitted by Earth and
clouds, between 10and 11um. Helps distinguish between high and low
clouds.Cold objects appearbright, warm objects appeardark
WaterVapourimagery:Satellite must sense radiation with awavelength of
6.7um (strongly absorbed by water). Mois appearbright on infrared imagery -
depicts where in the atmosphere has high watervapourcontent.
Radar:useful forthe reflected pulse returns as it indicates the distance to the
storm, the reflected pulse indicates the types and intensity of precipitation.
(Dopplerradar=popularforfinding areas of heavy rain, hail in storm and
2. Analysis: involves compiling and mapping the data(Gathering)
3. Diagnosis: involves developing an understanding of the processes at work
4. Prognosis: generation of the forecast. (Presenting)
1. Persistence Forecasting:Ideais, what will happen now will happen in the future
EX: - winterweatherrain will last afew hours
- dry spell in the summerwill be several days 2. Trend Forecasting:ideais, the weathersystems often move in the same direction
and speed as they’ve been moving. This trend holds as long as upper-airlong-wave
patterns don’t change.
3. AnalogorPattern-Recognition:involves comparing acurrent weatherpattern with a
weatherpattern in the past.
based on observations of atmosphere-ocean cycles
•El Niño–Southern Oscillation (ENSO)
•North AtlanticOscillation (NAO)
•PacificDecadal Oscillation (PDO)
4. Empirical forecastingor“rule of thumb”:rules are based on past observations.
5. Climatology:does not require knowledge of current weatherconditions, as it’s based
on statistics compiled overthe years. Forecasts are based on probability.
6. Numerical WeatherPrediction (NWP):numerical model programed in computers.
the forecast is therefore calculated.
The atmosphere an example of a“chaotic”system:
•Slight differences in initial conditions can produce quite different forecasts
•Errors are amplified (and accuracy decays) overtime
•24hours is usually accurate
•2–5days is fairly accurate
•7+days - accuracy decreases rapidly
- Numerical methods used to find approximate solutions
- Computermodels represent the atmosphere using athree-dimensional grid
- can only represent eitherGlobalorRegional Supercomputers are programmed with models that use equations to mimicthe atmosphericprocess,
these equations are known as “primitive” equations - fundamental laws governing atmospheric
(Bjerknes: 7equations describe 7variables important to controlling the weather)
•Two equations of motion (PGF, CF, Friction)
- represents the horizontal movement of air
-represents the vertical motions
•Ideal gas law
- represents pressure
•First law of thermodynamics (conservation of energy)
- determine temperature
•Conservation of mass
•Conservation of moisture
Time steps: when the model starts up, the first set of calculations advances the initial values forward
in time by one time step. The new values are then used to calculate the values forthe next time step
Global Environmental Multiscale (GEM) these models are not produced in detailed forecasts only
shows averages (used in Canada)
Ensemble forecastingruns the same model several times forthe same period.
•Initial conditions are varied slightly each time
•Produces arange of possible outcomes
- the average of these outcomes might be used as the forecast also be used to
define the uncertainty in aforecast.
- inevitable errors and gap in weatherobservations
- impossible to make amodel represent reality perfectly
- grid system =crude approximation
- lack in understanding of atmosphericprocess
- limits in computational power
- weatheris chaotic: can’t predict exact sequence of events
Long-Range Forecasting:based on climatology ratherthan modelling - use of past patterns to predict
- offers probabilities ratherthan specifictemperature orweather.
Teleconnections:Interactions between the ocean and the atmosphere, the warming
and cooling of the Pacificinfluences global wind patterns thus affect weatheraround the
world.Link Analog observation of atmosphere-ocean cycle patterns to atmospheric circulations around the world
EX: Shifts from upperairflow can causes places to be wetterordrierthan normal.
- can make western Canadawarmerin winter
- common floods ordroughts during strong episodes
- can make western Canadacolderin winter
Lecture 20- Chapter16
Climate Control:Certain types of weatherwill characterize aplace, creating the climate of that place.
- create climate types that influences othercharacteristics of the location
EX: agriculture, forestry, recreation and tourisms etc
- Nearequation:hot and wet all yearround
- Places interiors of large continents:large seasonal variations in high-latitude
- Coastal locations:less seasonal variations
- Windward mountainous coasts:wet conditions / coastal deserts in otherareas
1. Latitude: it controls the sun’s angle and day length, majordeterminant of temperature, seasons.
- tropics: torrid zone
- mid-latitudes: temperate zone
- polarregions: frigid zone
(always cold because of sun angles are low overthere)
2. Distribution of Land and Water:account fordifferences in climate formarine and continental
locations. Proximity to watercan cause wetterclimates and exhibits smallerdaily and annual
variations in temperature.
3. Ocean Currents:warm orcold currents can affect temperature and precipitation.
- Warm currents carry energy that is shared with coastal climates (warmth, instability)
- Cold currents bring cold temperatures and stable air(may also be associated with low
4. Pressure Systems:controls precipitation, rememberthe 3majorpressure systems:
the equatorial low (wet at equatorand mid latitudes), the subtropical highs (dry) and polar
Average pressure patterns control precipitation Low pressures =frequent precipitation
High pressures =dry climates
5. PrevailingWinds:can affect both precipitation and temperature.
- Tropics: easterly trade winds
- Mid-latitudes: westerlies
- west of canadais strongly affected by the effect of the ocean than in the east
- these winds determine the locations of rain-shadow deserts
6. Mountains:they control climate by acting as barriers that force airto rise and release moisture as
precipitation on theirwindward sides; having lost its moisture, the airsinks on the leeward sides of
the mountain produces deserts.
Climate Classification:Maps of specificquantities such as temperature and precipitation are easy to
produce. Useful classifications of climate are more difficult. Applied Systems:when maps are created foraspecificuse
- Derived indices calculated from climate data
Empirical Systems:climates are grouped based on observed data. usually temperature and
precipitation. GeneticSystems:climates are grouped based on theircauses
ex. the constant hot, wet conditions nearequatorare caused by the consistently high
sun angles and close proximity of ITCZ (The Intertropical Convergence Zone)
- can use climate control, like pressure and latitude, to explain characteristics of
The Koppen System:(An empirical system)
- Based on the assumption that vegetation is closely linked to climate
- Simplicity: system uses monthly values of temperature and precipitation to define broad climate
*classifies climate based on theirtemperature and precipitation data (looks like the above)
5Majortypes of Climates
•Tropical rainy climates
- avg. temperature every month is 18’C orhigher
- tropical rain forests
- formoisture deficit to occurthe potential evaporation must exceed precipitation
•Mid-latitude rainy climates with mild winters
•Mid-latitude rainy climates with severe winters
•Polarclimates: cold and dry
- warmest month =below 10’C (associated w/northern limit of tree growth) How it works (details below) A, C, & D- are considered warm and moist enough to support growth of forests.
- forthese 3moist climates asecond letteris used to indicate the seasonal distribution of
precipitation. (based on if theirsummeris dry, winterdry oreven distribution of precipitation.)
B. C & D- this climate groups are given a3rd letter.
ForBthe letteris used to distinguish between hot and cold deserts.
ForC &Dthe letteris used to provide more detail about the seasonal temperatures.
main climate controls influencing tropics:
- low latitudes (30’N to 30’S)
-Pressure systems: ITCZ (equatorial low) and subtropical highs
- easterly trade winds: makes it wetterthan tropical west coasts
Af - Wet Equatorial Climates
- hot and wet all yearround
- normally close to equator, 10’N and 10’S
ex. Amazon Basin of South Africa=largests areaof this climate
Am- Tropical Monsoon Climates
- always hot, distinguished by theirseasonal precipitation regime.
- dry season of 3to 6months during low-sun seasons
- Monsoon climates =highest amount of precipitation on Earth (ex. 11,000mm)
ex. Southeast Asiaand India=largest area
Aw- Wet-Dry Tropical Climates
- have seasonal precipitation regime, wet season =high-sun season but less
precipitation and short (u