UVic GEOG 272 midterm 1

Meteorology

the study of weather -> instantaneous conditions of the atmosphere at a specific place and time (short term)

Climatology

study of behaviour of atmosphere integrated over a long period of time

climate statistics use ___ years of records to create a climate normal

30

climatology looks at

variability and extremes (max/min) of weather and anomalies and frequencies

normals

average weather conditions at a given place (30 years)

frequencies

rates of incidence of a particular phenomenon at a particular place over a long period of time - important for planning

extremes

max and min measurements of an atmospheric variable that can be expected to occur at a certain place and time - can happen infrequently, hard to study

What are the 5 scales in climatology

- microscale

-local scale

-mesoscale

-synoptic scale

-planetary (global) scale

Microscale

-smallest of all atmospheric scales

-phenomena that operate along spatial scales smaller than 0.5 km and temporal scales of seconds to hours

Local scale

phenomena that operate along a spatial scale of 0.5-5km and temporal scale of hours

Mesoscale

phenomena that operate along spatial scales 5-100km and temporal scale of days

Synoptic scale

phenomena that operate along a spatial scale of 100-10,000km and a temporal scale of days to weeks

Planetary (global scale)

phenomena that operate along spatial scales of 10,000-40,000km and temporal scales of weeks to months

3 main sources of energy

- the sun

- force of gravity

- internal heat of the core and mantle

lithosphere

- crust and upper mantle

- solid rock layer

~ 100km thick

Asthenosphere

- hot and slowly flowing layer of relatively weak rock

Mesosphere

lower part of the mantle where rock is very highly coompressed

mantle

solid iron and magnesium rich rock, reaching down to 3000km below surface

outer core

liquid iron and metal

inner core

mainly solid iron and nickel - size of the moon

hydrosphere

combined mass of water found on, under, and above the surface of the Earth

cryosphere

frozen water in all its forms (glacial ice and snow, permafrost, sea ice, sea shelves, etc.

continuous permafrost

forms at mean annual air temp. below 5C and is laterally continuous, regardless of surface aspect or material

discontinuous permafrost

forms where the mean annual air temp is between -2C and -4C allowing permafrost to persist in 50-90% of the landscape

Biosphere

all living organisms, the worldwide sum of all ecosystems

ecosystems

communities of interacting organisms and their relationships with the lithosphere, atmosphere, and cryosphere

atmosphere

envelops the Earth: mixture of gas molecules and aerosols

aerosols

microscopic suspended solid/liquid precipitation, soot particles, salt crystals

hydrostatic equilibrium

opposing forces from gravity and buoyancy

buoyancy

all liquids and gases in the presence of gravity exert an upward force

initial atmosphere

- developed 4.5 billion years ago

- Hydrogen, Helium, Neon, Argon in large concentrations

- gases swept away by solar winds

- not in hydrostatic equilibrium

development of today's atmosphere

- out-gassing of volcanic material released from steam (H2O), CO2, nitrogen, and methane

- condensation formed oceans

- anaerobic bacteria began to photosynthesize (3.5 BYA) producing O2 and CO2

- increased oxygen created ozone which blocked UV radiation resulting in terrestrial plants and again more oxygen

Composition of the atmosphere today

Gas Molecules

- Constant Gases: nitrogen, oxygen, argon

- variable gases: carbon dioxide, water vapour, methane, Nitrous Oxide, Ozone, CFCs

Aerosols

- ice crystals, volcanic soot, salt crystals, soil particles, clouds, fog droplets

constant gases

nitrogen, oxygen, argon

- long residence times

- comprise 99% of atmosphere

- concentrations do not vary much

- have little/no effect on meteorological and climate processes

Aerosols

Ice crystals, volcanic soot particles, salt crystals, soil particles, clouds, fog droplets

- particles suspended above the Earth's surface that are too tiny to be pulled down by gravity

- less than 0.003% of atmosphere

- have a large impact on weathering and climate

variable gases

carbon dioxide, water vapour, methane, nitrous oxide, ozone, CFCs

- about 0.04% of atmosphere

- quantities change considerably over time

- substantial importance for weather, climate, and temperature

Carbon Dioxide (CO2)

- removed by photosynthesis

- added by plant/animal respiration, decay of organic material, volcanic eruptions, and combustion

- changes induce important climatic consequences

Ozone (O3)

- stratospheric zone is essential to protecting life from harmful UV radiation

- ground-level ozone can be a serious air pollutant (harms lungs, eyes, and vegetation)

Methane (CH4)

- important and effective GHG

- rice cultivatio, biomass burning, and fossil fuel extraction have all contributed to increases of methane in the atmosphere

Division of atmosphere

- divided into layers based on thermal properties

- no distinct upper boundary (atmosphere becomes less dense with height)

density

average distance a molecule travels before colliding with another molecule

Troposphere

- lowest layer of atmosphere

- thinnest layer but contains 75-80% of atmospheric mass and nearly all weather and water

- depth ranges from 8-16km

- temp. decreases with height

Stratosphere

- temp. increases with height due to absorption of UV radiation by ozone (bottom of stratosphere)

- extends from tropopause upwards about 50km

- contains less than 20% of atmospheric mass

- troposphere and stratosphere account for 99.9% atmospheric mass

photodissociation

- O2 molecules absorb UV radiation at wavelengths of 120-180 nm

- sometimes radiation can split the oxygen atoms

- a single oxygen atom can then combine with O2 to form more ozone (O3)

- ozone absorbs UV radiation at wavelengths between 180-340 nm

- radiation 340-400 nm can still reach surface

mesosphere

- temp decreases with height

- extends 50-80km above surface

- almost all of the remaining 0.1% of mass located here

- few weather/climatic processes due to so little mass

thermosphere

- top layer

- temp. increases with height as O2 and N2 molecules absorb shortwave radiation

energy

the quantitative property that must be transferred to an object/substance in order to do work

- standard unit is the Joule (J) but sometimes calorie

power

the rate at which work is performed (energy is released, transferred, or received)

- standard unit is the watt (W)

W = J/s

kinetic energy

energy of motion

potential energy

stored energy

atmospheric/climatic system is always attempting to...

disperse energy

the sun

the main driving force of energy driving atmospheric and ocean circulation due to uneven heating of the Earth

Insolation

the amount of solar radiation received by the Earth for a given surface in a given time period

where does energy come from?

E is converted matter through the nuclear fusion of 4 hydrogen into a helium atom

- during this process some of the mass is converted to energy

- process occurs in the sun's core

electromagnetic radiation

- transmission of energy in the form of waves and/or particles through stuff or empty space

- can cause particles to move up and down

- can travel through nearly anything at the speed of light

characteristics of wavelength and frequency

- wavelength is the distance between two crests

- frequency refers to the number of wavelengths that pass through a fixed point in 1 second

- shorter wavelengths have higher frequencies, cause particles to move more

electromagnetic spectrum

- sun emits radiations at all wavelengths

- 44% falls within visible light, 44% in thermal infrared, and the rest is UV

- visible light is 400-700nm

radiant energy

drives the Earth's atmospheric and oceanic circulations, as well as biosphere

first law of thermodynamics

Energy can be transferred and transformed, but it cannot be created or destroyed.

second law of thermodynamics

energy flows from areas of high concentration to areas of lower concentration

Temperature

a measure of the average speed atoms and molecules which make up a substance

heat

energy in the process f being transferred from a substance (or object) with a higher temp. to a substance (or object) with a lower temp.

conduction

movement of heat across adjacent molecules, no movement of mass

- spread through direct contact

- heat transferred via conduction where air meets the surface

convection

involves movement of mass through sensible heat fluxes and latent heat fluxes

Stefan-Boltzmann Law

determines the amount of energy emitted by each square meter of an object's surface

E = total energy emitted (flux density) Wm^2

sigma = SB constant

T = surface temp. K

- states that all objects with temperatures above absolute zero emit radiation at a rate proportional to the fourth power of their absolute temperature

absolue zero

0K or -273C

Wein's Law

determines the wavelength of maximum emission for a black body at a given temperature

lamda = peak/max wavelenth emission (um)

constant = (umK)

T = surface temp. K

How do we determine how fast heat is conveyed by conduction?

Ohm's law

Flow rate = potential for flow to occur * conductivity

conductivity - measure of ease with which energy passes through material (inverse of resistance)

Thermal conductivity (K)

the measure of a substance's ability to conduct heat from one molecule to the next

- different for different materials

- air is a good insulator

Fourier's Law

(aka law of heat conduction) The transfer of heat moves through matter from higher temperatures to lower temperatures in order to equalize differences.

total heat flux Wm^2

dt = T1-T2

dx = X2-X1

heat transfer in soils

Qg = soil heat flux or ground heat flux

flux of heat gets:

- larger with increasing temp. difference

- smaller the further that heat difference has to flow

- dependent on this thermal conductivity of the soil/material

Why does K increase a you add water to soil?

water has a higher conductivity than air and more molecules are touching which results in a higher heat flux

radiation or convection in soils?

convection in tightly packed soil is slow and radiation is very slow

convective heat fluxes

- process by which energy is transferred vertically, from the surface to the air

- requires the movement of mass (air or water molecules)

- carried by these molecules as heat or phase change

Sensible heat flux (Qh)

- related to changes in temp. of a gas or liquid (no phase change involved)

- occurs when more energized molecules in a fluid or gas rise and less energized molecules sink

*uses same Fourier's law equation

Latent heat (Qe)

dominant convective process compared to Qh

- process of melting, evaporating (energy is consumed)

- process of condensing, freezing (energy is released)

when hot air rises it...

cools and condensates -> energy is then released

Plank's law

E = hc/lambda

measures the amount if energy emitted by a certain wavelength

shortwave radiation (K*)

- radiant energy with wavelenths in the visible, near-ultraviolet, and near-infrared spectra

- encompasses wavelengths ~0.1 to 4um

incoming solar radiation (Kv)

incoming solar radiation is most intense, and is involved in multiple processes when entering the atmosphere (transmission, absorption, scattering [direct or diffuse], and reflection)

transmission

some wavelengths of energy can propagate directly down to Earth's surface - small proportion of E is transmitted (doesn't interact with atmosphere)

absorption

retention by an atmospheric particles, and conversion to internal energy aka heat

scattering

redirection of energy as weaker rays as energy is "lost" (converted into different forms of energy)

direct radiation

radiation that reaches Earth without scattering

diffuse radiation

radiation that reaches Earth via scattering

reflection

energy reflected off the tops of clouds or surfaces of the Earth, back into space at the same angle and thus does not contribute to heating of planet

where might you see lots of diffuse radiation?

areas with lots of pollution or cloud cover

albedo

the amount of energy that is reflected by a surface

- high albedo near the poles due to ice sheets, lower at the equator

incoming shortwave radiation

~30% of Kv is reflected back by clouds (planetary albedo)

25% is absorbed by air

25% direct radiation (no scattering)

20% diffuse radiation (after being scattered)

- fairly constant amount of shortwave radiation incoming

What happens at night?

No incoming shortwave radiation

we have longwave radiation emitted by the Earth

longwave radiation (L*)

longwave radiation is 4-100um

Earth absorbs shortwave radiation (Kv) from the sun and re-emits longwave energy (L*) in all directions

L^ - emitted by surface

Lv - emitted by air

where does longwave radiation go?

- 7-15% of L^ is transmitted back to space

- a lot of L^ is captureed by the atmosphere (clouds, water vapour, GHGs) about 85-93% is re-emitted back to Earth's surface

what is surface net radiation (Q*)?

defined as the difference between incoming solar radiation absorbed at a particular point at the Earth's surface and the radiation reflected back to space

- can be +/-

- varies lots over time and location

surface net radiation budget

Q* = Kv(1-a) + (Lv -L^)

where a is surface albedo

Is Q* positive or negative at night?

negative

Kv and K^ are zero and (Lv-L^) is slightly negative as the sun tends to heat the surface more than the air

Is Q* positive or negative during late afternoon?

positive

(Kv-K^) is a large positive number because only a small % of shortwave radiation is reflected upwards which is usually enough to outweigh a negative (Lv-L^) value

generalities for Q*

- Q* is inherently tied to temperature changes at the surface

- if Q* is positive there is a surplus of energy and temperature rises

- if Q* is negative there is a deficit of radiant energy and temperature falls

- if we totaled surface Q for all areas of the Earth we would find a surplus of energy and if we totaled air Q we would have a deficit

if energy occurred by radiation alone the surface would be ______ and the air would be ______

the surface would be warm and the air would be cool

what else plays a role in moderating change in temperature of air

convective evaporate / latent heat fluxes (Qe) and convective sensible heat flux (Qh) and conductive ground heat flux (Qg)

the energy balance equation

where Q* = Qg +/- Qh +/- Qe

or

Kv(1-a)+(Lv-L^) = Qg +/- Qh +/- Qe

this equation states that the sum of the NET shortwave (K) and longwave (L) radiation received at a given surface must be balanced by the convective loss of energy upward through Qh and Qe, as well downward through the conductive loss Qg