Climatology: Midterm

Front 1

troposphere

Back 1

lowest layer of the atmosphere

Front 2

Planetary Boundary Layer

Back 2

(in troposphere) well-developed mixing, friction, convection; depth varies diurnally: is thicker (2 km) during the day, thinner at night

Front 3

Turbulent Surface Layer

Back 3

(in troposphere) intense small scale turbulence due to surface convection, roughness thicker during the day (50m), thinner at night; time scale: seconds;

To

understand

the

transfers

in

the

turbulent

surface

layer

we

will

use

the

principles

of

the

laminar

layer.

The

major

difference

is

that

we

will

use

the

eddy

diffusivity

instead

of

the

molecular

diffusivity

since

the

transfer

is

largely

due

to

eddy

activity

rather

than

molecular

activity.

The

eddy

diffusivities

are

not

constant

like

the

molecular.

Rather,

they

vary

over

time

and

space.

Front 4

Roughness Layer

Back 4

(in troposphere) depends on height of roughness element--> buildings, trees, etc.; can be 1-3 times the height of roughness element;

Exchanges of heat mass and momentum occur

but

they

are

dif>icult

to

express.

Flows

are

very

complex.

We

will

generalize

as Necessary.

Front 5

Laminar Boundary Layer

Back 5

(in troposphere) depends on wind speed

Front 6

Energy

Back 6

ability/capacity to do work

Front 7

Work

Back 7

force applied over distance or movement of matter over distance (Newton meter, Nm)

Front 8

Force

Back 8

Mass X acceleration (Newton, N)

Front 9

Acceleration

Back 9

rate of change of speed (meters/secondsecond)

Front 10

Thermal Energy

Back 10

Mechanical energy converted to calories (1 calorie= 4.186 Joules; Joule=Nm)

Front 11

Kinetic energy

Back 11

motion

Front 12

Gravitational Potential Energy

Back 12

associated with the height of an object above a surface

Front 13

Sensible Heat

Back 13

internal energy which may be sensed or measured, for ex: by thermometer

Front 14

Latent Heat

Back 14

energy involved with the changes of state of water

Front 15

Latent heat of condensation –

Latent heat of evaporation –

Latent heat of sublimation –

Latent heat of fusion –

Back 15

-released when water vapor changes to liquid

-absorbed when water changes from liquid to gas (vapor)

-absorbed when ice changes to water vapor

-released when ice changes to liquid

Front 16

Blackbody

Back 16

emits radiation at the maximum possible intensity for every wavelength and temperature to the emitance of an ideal blackbody at the same wavelength and temperature

Front 17

Absorptivity

Back 17

the ratio of the amount of radiant energy absorbed to the total amount incident upon that surface. The emissivity of a blackbody is unity (1)

Front 18

Radiant flux

Back 18

rate of flow of radiation (Js-1)

Front 19

Radiant flux density

Back 19

radiant flux per unit area (Js-1m-2)

Front 20

Irradiance

Back 20

radiant flux density incident upon a surface

Front 21

Emittance

Back 21

radiant flux density emitted by a surface

Front 22

Quantity depends on...

Back 22

1. intensity of the sun's emittance (radiant flux density emitted by a surface)

2. time of day

3. time of year

4. atmospheric transparency

Front 23

Intensity of sun's emittance

Back 23

– Stefan-Boltzman and Wien's Laws

- Solar Constant 1370 Watts per square meter

- angle of incidence affects the radiant intensity of the flux of energy

Front 24

path length of radiation through the atmosphere

Back 24

time of day - It is longest near sunrise and sunset and shortest near noon.

time of year - It is shortest at summer solstice and longest at winter solstice.

Front 25

Scatter

Back 25

occurs when gas molecules intercept and “knock out” parts of the Electromagnetic spectrum.

Front 26

Rayleigh scatter

Back 26

occurs in the blue part (very small wavelengths) of the EM spectrum

Front 27

Mie scatter

Back 27

occurs across all wavelengths e.g. in clouds

Front 28

Turbidity

Back 28

any condition of the atmosphere that reduces its transparency to radiation

- dust, aerosols, pollen, haze

Front 29

Quality (of solar radiation)

Back 29

Some gases remove some wavelengths of solar energy

e.g. ozone and oxygen remove UV radiation in the visible part of the spectrum there is not much absorption except at the longer (red) wavelengths where water vapour and carbon dioxide absorb energy.

Front 30

Diffuse Radiation

Back 30

This is the radiation that reaches the earth after being scattered from the direct beam by atmospheric gases. It is very important at high latitudes (longer path length) and during winter (same reason) before sunrise and after sunset.

Front 31

Shortwave reflection

Back 31

Some of the solar radiation that reaches the surface of the earth is reflected. The amount of energy reflected depends on the albedo of the surface.

Front 32

albedo

Back 32

is the capacity of a surface to reflect shortwave radiation. It is described as a percentage.

Front 33

Long wave radiation

Back 33

energy emitted at longer wavelengths by cooler bodies

Front 34

Convection

Back 34

vertical exchange of air – occurs in liquids and gases. It involves the actual movement of air and its properties from one place to another.

It is the most effective form of transfer and mixing in the atmosphere. - Eddies, thermals. Latent and Sensible Heat are transferred in this manner.

Front 35

Conduction

Back 35

occurs via the collision of molecules. Is important in the laminar layer. Energy is transferred by contact

Front 36

ENERGY BALANCE

Back 36

Top of Atmosphere: I = O

Atmosphere I > O

Earth Surface I > O

Front 37

Active surface

Back 37

is a plane, infinitesimally thin. It has no mass and no energy but it is the chief site of the exchanges of energy and mass in the system. It is here that energy is absorbed, reflected, emitted and major energy conversions take place.

Front 38

Specific Heat –

Back 38

a property of mass (kg) – is the amount of energy it takes to raise the temperature of one unit mass of a substance by 1 degree Kelvin

Front 39

Heat capacity

Back 39

a property of volume (m^3) – is the amount of energy it takes to raise the temperature of one unit volume of a substance y 1 degree Kelvin.

Front 40

Subsurface layer

Back 40

exchanges are mostly molecular with energy flowing from areas of high concentration to areas of low concentration. The rate of flow depends on the temperature difference between the two locations and the thermal diffusivity since most of the transfer occurs by molecular collisions transferring kinetic energy.

Front 41

lapse

Back 41

temperature decrease with height

Front 42

inversion

Back 42

temperature increase with height

Front 43

Ks

Back 43

are

the

molecular

diffusion

coef/icients

and

are

very

small.

This

means

that

transfer

is

slow.

In

this

way

the

laminar

layer

insulates

the

surface

from

most

of

the

atmosphere.

The

slowness

of

transfer

also

means

that

gradients

tend

to

be

steep

in

the

laminar

layer.

Front 44

Outer Layer:

Back 44

This is dominated by free convection - large eddies, thermals and heat plumes. It is of variable depth depending on turbulence at the ground. On sunny days it is at 1 - 2km but at night it can be as shallow as 100m. It may also be called the mixed layer. Climatic properties in this layer vary very little with height