Hurricane Katrina (August 29, 2005)

Lethbridge, Alberta

Current weather conditions

17h00 January 10, 2006 Mainly clear

Temp.:

5 °C

Pressure: Visibility:

99.7

kPa



32km

Humidity: DewPoint: Wind:

55% -3 °C SW 24 km/h

Weather Current state of the atmosphere air temperature atmospheric pressure humidity clouds precipitation visibility wind Climate Statistical analysis or characterization of what is normal or expected Long term averages *Means* *Extremes* *Variability*

78% N 2 21% O 2 H 2 O CO 2 CH 4 CFCs N 2 O O 3 Aerosols NO 2 CO SO 2 Hydrocarbons

Gravity pulls gases toward earth's surface 101.325 kPa

UNSTABLE STABLE

What happens to solar energy ?

1.

2.

3.

Absorption

(absorptivity=  )

Results in conduction, convection and long-wave emission

Transmission

(transmissivity=  )

Reflection

(reflectivity=  )  

+

 

+

 

= 1

Response varies with the surface type Snow reflects

40 to 95% of solar energy and requires a phase change to increase above 0°C

Forests

and

oceans absorb

more than

dry lands

Then why do dry lands still “heat up” more?

Oceans transmit

solar energy and have a high

heat capacity

Characteristics of Radiation

Energy due to rapid oscillations of electromagnetic fields, transferred by photons

The energy of a photon is equal to Planck’s constant, multiplied by the speed of light, divided by the wavelength

E = hv

 All bodies above 0 K emit radiation

Black body Emissivity,

 emits maximum possible radiation per unit area.

= 1.0

All bodies have an emissivity between 0 and 1

Electromagnetic Radiation

Consists of

electrical field

(E) and

magnetic field

(M) Travels at speed of light (C) The shorter the

wavelength

, the higher the

frequency

This is important for understanding information obtained in remote sensing

Stefan-Boltzmann Law

As the temperature of an object increases, more radiation is emitted each second

Temperature determines E,



emitted Higher frequencies

(shorter wavelengths) are emitted from bodies

at a higher temperature

Max Planck determined a characteristic emission curve whose shape is retained for radiation at 6000 K (Sun) and 300 K (Earth)

Energy emitted =



(T 0 ) 4 Radiant flux

or

flux density

refers to the rate of flow of radiation per unit area (eg., W  m -2 )

Irradiance Emittance

= = incident radiant flux density emitted radiant flux density

Wien’s Displacement Law

As the temperature of a body increases, so does the total energy and the proportion of shorter wavelengths



max = (2.88 x 10 -3 )/(T 0

) *wavelength in metres

Sun’s



max = 0.48



m

Ultraviolet to infrared - 99%

short-wave

(0.15 to 3.0  m)

Earth’s



max = 10



m

Infrared - 99%

longwave

(3.0 to 100  m)

Terrestrial radiation Solar radiation

Microwaves are longest wavelengths used in remote sensing We are blind to everything except this narrow band UV are shortest wavelengths practical for remote sensing

Transmission through the Atmosphere Some wavelengths of E-M energy are absorbed and scattered more efficiently than others H 2 O, CO 2 , and ozone have the strongest absorption spectra Transmission Light moves through a surface (eg. on a natural

8-11  m window

Wavelength dependent (eg. leaves) Radiation emitted from Earth is of a much longer wavelength and is of much lesser energy

ALBEDO: April, 2002

white and red are high albedo, green and yellow are low albedo http://profhorn.aos.wisc.edu/wxwise/AckermanKnox/ Earth's Albedo chap2/Albedo.html

Characteristic spectral responses of different surface types. Bands are those of the SPOT remote sensing satellite.

•white snow •old snow •vegetation •light colour soil 0.80-0.95

0.40-0.60

0.15-0.30

0.25-0.40

•dark colour soil 0.10

•clouds 0.50-0.90

•calm water surface 0.10 (midday)

NET ALL_WAVE RADIATION

DAYTIME: Q* = K



- K



+ L



- L



Q* = K* + L* NIGHT: Q* = L*

Radiation Balance Components

Source: NOAA

L

Conduction

The transfer of heat from molecule to molecule within a substance

Convection and Thermals

Convection

The transfer of heat by the mass movement of a substance (eg. air) Rising air expands and cools Sinking air is compressed and warms

•

Heat capacity

The ratio of the amount of heat energy absorbed by a substance to its temperature rise

•

Specific heat

The amount of heat energy required to raise the temperature of 1g of a substance by 1°C

•

Latent heat

The heat energy required to change a substance from one state to another

•

Sensible heat

Heat energy that we can feel and sense with a thermometer

Radiation Sensors

(PAR and K  )

Thermometer

and radiation shield SENSIBLE HEAT

Photo:

My Tausa, Cundinamarca, Colombia weather station (3243 m asl) Raingauge Datalogger

Check this out: http://www.jgiesen.de/sunshine/index.htm

N

-10 -15 -20 -25 -30 -35 -40 20 15 10 5 0 -5

Dec 15, 2004 Jan 19, 2005

10 cm Air Temp (south-facing) 10 cm Air Temp (north facing)

15 10 5 0 -5 -10 -15

Dec 15, 2004 Jan 19, 2005

10 cm Soil Temp (south facing) 10 cm Soil Temp (north-facing)

-10 -15 -20 -25 -30 -35 -40 -45 10 5 0 -5

Dec 15, 2004

10 cm Dewpoint (south facing) 10 cm Dewpoint (north facing)

Jan 19, 2005

10 – 100  m

0.0001 – 0.001  m

Mie scattering 0.01 to 1.0  m

LONG PATH LENGTH OF LIGHT THROUGH THE EARTH’S ATMOSPHERE MOST OF THE THE VIOLET, BLUE AND GREEN LIGHT IS SCATTERED

(from Pacific) (Prairie cold)

•

OUTGASSING

•

TORRENTIAL RAINS PRODUCED LAKES AND OCEANS

•

DISSOLVED AND UNDISSOLVED ELEMENTS

•

PRESENT VOLUME 1,360,000,000 km 3

•

VOLUME IS STABLE

Water Reservoir

Oceans Ice caps, glaciers Ground water Fresh-water lakes Inland seas Soil moisture

Atmosphere

Rivers

Percent

97.24% 2.14% 0.61% 0.009% 0.008% 0.005%

<0.001%

<0.0001% Source: U.S. Geological Survey

Some fast-moving molecules escape from the liquid

In cool air, H 2 O molecules are more likely to join nuclei

CHANGES DOES NOT CHANGE

MASS/VOLUME g H 2 O / m 3 air

Specific humidity

:

the mass of water vapour (g) per mass of air (kg) Maximum specific humidity

is the maximum mass of water vapour that can be held by 1kg of air at a given temperature

MASS OF WATER VAPOUR TOTAL MASS OF DRY AIR g H 2 O / kg air

A ratio that compares the amount of water vapour in the air to the maximum water vapour capacity at that temperature

The relative humidity of saturated air is 100% RH = [H 2 0 vapour content/H 2 0 capacity] x 100

The portion of atmospheric pressure that is made up of water vapour molecules

(mb or kPa) SATURATION VAPOUR PRESSURE: The pressure that water vapour molecules would exert if the air were saturated (at a given temperature)

RELATIVE HUMIDITY SPECIFIC HUMIDITY

Sling psychrometer

http://www.csgnetwork.com/canhumidexcalc.html

Why do surfaces facing the wind have more frost?

BLACK FROST

•

A surface is required for condensation

•

Condensation nuclei >0.1



m best

•

About 10-1000 large nuclei per cm 3 (more in lower troposphere and over land)

•

Hygroscopic or hydrophobic Source:

Dust, volcanoes, factory smoke, forest fires, ocean spray salt, sulphate particles from phytoplankton

Fog forms if T d is reached

Cold water advection fog

WHY DOES FOG FORM HERE?

Warm water advection fog

CAN ADVECTION FOG FORM OVER LAND MASSES?

YES

Pages 142-155 Laboratory Notes

Absolute stability Environmental lapse rate < moist adiabatic lapse rate

Environmental lapse rate > Dry adiabatic lapse rate

Solar heating of Earth’s surface Warm air advection at surface Air moving over a warm surface Cold advection Radiational cooling of clouds

LIFTING OF ENTIRE AIRMASS

Rainshadow