Atmosphere Flashcards
(112 cards)
1
Q
What are the layers of the atmosphere?
A
Troposphere
Stratosphere
Mesosphere
Thermosphere
2
Q
What can we define as the edge of space?
A
Karman line - 100km
3
Q
What part of the atmosphere does weather occur in?
A
Troposphere
4
Q
What is the relationship between temperature and altitude?
A
Troposphere temperature decreases with increasing altitude
Lapse rate
5
Q
What is lapse rate?
A
R = change in temp/change in altitude
6
Q
What is the average lapse rate in the troposphere?
A
6 degrees C/km
7
Q
What is lapse rate dependant on?
A
Water content in the air
8
Q
What is the tropopause?
A
End of the troposphere, varies with latitudes - highest at equator
30-40000 ft
9
Q
What is the dry adiabatic lapse rate (DALR)?
A
Air pressure decreases with altitude - cools very fast
9.8 degrees C/km
10
Q
What is the saturated adiabatic lapse rate (SALR)?
A
When dew point =
Condensation of latent heat, warming surrounding air
11
Q
What dos the SALR depend on?
A
How much water vapour is in the air i.e. more = more heat released
12
Q
What is pressure?
A
Force/area
Hectopascals (1hPa = 1mb)
13
Q
What is the global mean sea level pressure?
A
1013.25hPa
14
Q
What is the pressure at the top of the atmosphere?
A
~100hPa
15
Q
What is the ideal gas law?
A
Pressure x volume = no. Of moles x ideal gas constant x temperature (K)
16
Q
What is the ideal gas constant
A
8.314 J/K/mol
17
Q
What is a convective cell?
A
A region of rising air and sinking air
18
Q
What has lower atmospheric pressure: warm or cold air?
A
Warm air lower atmospheric pressure
19
Q
What does differential heating lead to?
A
Different weather
20
Q
What causes a low pressure system
?
A
Air rising
- cyclone
- clouds
21
Q
What causes a high pressure system?
A
Air sinking and diverging
- anticyclone
- sunny weather
22
Q
What is wind?
A
The movement of air from high pressure to low pressure
The greater the difference in pressure, the greater the speed of wind
23
Q
How do we calculate the pressure gradient?
A
= change in pressure/distance
24
Q
What is PGF?
A
Pressure gradient force
Net force directed from high to low pressure
25
What is an isobar?
A line of constant pressure
Large pressure gradient = tight isobars = large pgf
26
To what angle is wind in the atmosphere to the pressure gradient>
Perpendicular to pressure gradient
Parallel to isobars
27
What determines the global energy budget?
Balance between :
Solar energy absorbed by earth (shortwave radiation)
Infrared radiation emitted to space (long wave radiation)
28
What does incoming solar radiation vary with?
Latitude and season
29
What does outgoing infrared radiation vary with?
Local surface temperature
30
Where is there a surplus and deficit of energy?
Surplus at equator
Deficit at poles
Tries to balance itself out = weather
31
What creates atmospheric temperature and density differences?
Latitudinal energy gradient forces circulation of warm air to poles, cold air to tropics
32
What is the general circulation pattern?
Energy surplus at tropics - warm air rises = convection, cools at height - low pressure at surface and deep clouds
ITCZ
33
What marks the ITCZ?
Extensive cloud cover and heavy rainfall
Very calm air - no wind = doldrums
34
What warms the stratosphere?
Ozone absorption of UV radiation
35
Why does rising air diverge (spread out) at the top of the troposphere?
Has cooled with altitude, stratosphere acts as a lid so spreads out
Sinks and gains energy at dry adiabatic lapse rate = Hadley cell
36
What is the mid latitude polar front?
30-60 degrees
Cold air sinking at poles = high pressure = spreads out southwards
Meets warm air spreading north from downward limb of Hadley cell
Warm air rises over cold air, condensates therefore rainfall = ferrel cell
37
Why is wind deflected?
Rotation of earth
38
what is the three cell model?
hadley, ferrel, polar
39
What is convection?
Warm air rising
40
What is subsidence?
Cold air sinking
41
What is the coriolis effect?
The tendency for a fluid to be deflected from its straight line path due to the rotation of the earth
42
What is the north south case of the coriolis effect?
In northern hemisphere:
North-south motion deflects to the west
South-north motion deflects to the east
Vice versa in southern hemisphere
43
What is the east west case of the coriolis effect?
Centrifugal force acts perpendicular to axis of rotation - pushes air away from centre of rotation = eastward moving winds go towards the equator, vice versa for western winds
44
What way does earth rotate?
Anticlockwise
45
What is geostrophic wind?
When the pressure gradient force balances the coriolis force, resulting in wind direction parallel to isobars
46
What takes energy from winds?
Friction of uneven surface of earth
Cities vs beach vs mountains vs flat field
47
What are the winds?
Polar easterlies
Polar front
Mid latitude westerlies
Trade winds
Doldrums
48
What is meridional flow?
North<-> south
Polar, ferrel and Hadley cell
49
What is zonal flows?
West<-> east winds
Trade winds, walker circulation, jet streams
50
How is wind velocity a vector?
(U, V)
Zonal and meridonial component
51
What drives walker circulation?
Zonally asymmetric (mountains, pacific, desert)
Differences in temperature = differences in convection (land gets hotter faster than sea)
52
What are jet streams?
Narrow bands of fast moving air
Ie subtropical jet (poleward edge of Hadley cell), polar jet (poleward edge of ferrel cell)
53
What direction do westerlies travel?
From the west to the east
54
What direction do jet streams travel?
Westerlies in both hemispheres
55
What are the characteristics of jet streams?
1000s km in length
100s km wide
Few km thick
5-15km above surface
>200km/h
56
What is the importance of jet streams in mid latitudes?
Polars jet steers weather systems
57
What distorts the idealised cell model?
Friction
Seasonality (pole to equator energy gradient greatest in the winter hemisphere), ITCZ distance greater to pole (ie southeast Asian monsoon)
58
why does wind accelerate?
moves from high to low pressure due to the pressure gradient force
59
what is the name for changes in climate over months-seasons-years?
climate variability
60
what is the name for changes in climates over multiple decades?
climate change
61
what is the main driver of large scale climate variability from seasons to years?
El Nino Southern Oscillation (ENSO)
62
Where do we see the warmest and coldest sea surface temperatures (SSTs)?
warmest - maritime continent ie indonesia, north australia
coldest - eastern pacific
63
what do warm SSTs dicate?
the location of the region of strongest ascending air- convection, rainfall
64
what is ENSO?
Irregular but periodic variation in winds and SST in the tropical pacific
65
what are the phases of ENSO?
El Nino - SSTs warmer than average
Neutral - SSTs close to average
La Nina - SSTs colder than average
66
what is the duration of ENSO?
Event is 1 season to multiple consecutive winters
period 2-7 years
67
what is the consequence of ENSO?
alters the location of convection in the tropics
68
what led to the discovery of ENSO?
1877 no indian monsoon = crop failure
Gilbert walker
69
what is La Nina?
enhancement of the average pacific conditions = strengthening of walker circulation
stronger winds = stronger upwelling = cooler SSTs in East Pacific
warmer STTs in West
70
what is El Nino?
a weakening or reversal of the average state
weaker easterly winds = less upwelling= warmer SSTs in E Pacific
High pressure in W pacific
71
how do we measure ENSO?
Measure ocean or atmospheric components
Southern Oscillation Index = Tahiti - Darwin sealevel pressure
SST anomalies
Nino 3.4 region
72
what is an anomaly?
anomaly = observation - mean
73
what is the coupling of the southern oscillation index and oceanic indices?
anticorrelated
74
what is Super Nino?
extreme events with higher amplitude
75
what is temperature in relation to flucations?
Temperature = Mean Temperature + Temperature Variability
76
what is evidence for ENSO in the past?
corals & trees - annual growth bands
SST reconstructions
77
what is variability?
wiggles in a time series
wiggles over long period = low frequency
wiggles over short period = high frequency
78
what is the ideal gas law in terms of density?
Pressure = density x specific gas constant for dry air x Temperature
79
what is density equal to?
mass/volume
80
what is the specific gas constant for dry air Rd?
287 J kg-1 K-1
81
what is the first law of thermodynamics?
conservation of energy within a closed system
82
what is hydrostatic balance
force balance between vertical pressure gradient force and gravity
83
what is an adiabatic process
When a material undergoes a change in physical state without any heat being added/removed
84
what is the dry adiabatic lapse rate
r dry = -change in temperature/change in distance = gravity /cp
= 9.81/1004 = 9.8 K km-1
85
what is potential temperature?
what temperature a parcel could be if it moved vertically or experience a different pressure
O/ = T (p0/p)^Rd/cp
86
what is work done?
Force x distance moved
87
how do we represent an infinitesimal change in change in energy?
differentials
d change in energy = d thermal energy - d work
du=dq-dw
88
what are the assumptions for an air parcel?
moves slowly enough that the kinetic energy of the parcel is negligible
is thermally insulated from environment
89
what is cp?
1004 J K-1 kg-1
90
what is a boundary layer?
a thin layer of a fluid in contact with a surface
91
what its the planetary/atmospheric boundary layer?
the lowest part of earths atmosphere influenced by the surface on a timescale of hour in which friction and turbulence dominate
92
what is the surface radiation balance?
net radiation flux = short wave (solar) flux in - short wave flux out + longwave (terrestial) flux in -longwave flux out
F* = Fs in - Fs out + FL in -FL out
93
what is the relationship between radiation and temperature?
hotter things emit vastly more radiation
E = Ɛ σ T^4
energy = emissivity x5.67x10-8 x temp ^4
94
what is the diurnal cycle in radiation?
no shortwave radiation received at night
incoming shortwave varies with sun angle
reflection - shortwave albedo
longwave affect by temp, peaks late noon
95
what determines if latent or sensible heat dominates?
surface moisture availability
96
what is turbulence?
when a flow contains superimposed swirls of many different sizes
97
what is a swirl (in terms of turbulence)>
eddies
98
what happens if there is no turbulence?
laminar flow
99
what is a benefit of turbulence?
is an effective mixer
100
What is TKE?
Turbulence kinetic energy
= 1/2 (σu^2 +σv^2 + σw^2)
0 when laminar flow
101
how do we represent the change in TKE due to components?
change in TKE/change in time = advection + mechanical + buoyancy + transport - diffusion
102
what is advection?
movement of TKE by mean wind
positive or negative
103
what is mechanical?
generation of turbulence by wind shear
positive or zero
104
what is buoyancy?
generation or consumption pf turbulence by density differences
positive or negative
105
what is transport?
movement of TKE by turbulence itself
positive or negative
106
what is dissipation?
the destruction of turbulence by the viscosity (internal friction) of the flow
always positive
107
what is roughness length z0?
the theoretical height at which winds drop to zero
108
what is the vertical structure of the boundary layer?
free troposphere
entrainment zone/capping inversion
mixed/residual layer
surface layer (10% depth)
109
what is characteristic of the summer seasonal cycle?
stronger solar radiation
more intense heating
air rises more readily
stronger mixing
boundary layer deep and well mixed
fluffy cumulus clouds
lower pollutant concentrations - mixing
weaker overnight stability due to shorter nights and less cooling
110
what is characteristic of the winter seasonal cycle?
weaker solar radiation
near surface cools for longer - long nights
less vertical motion = less well mixed
low angle of sunlight
shallow boundary layer with pollutants and moisture trapped near the surface
persistant fog
111
how is a cool sea breeze created?
in summer land warms faster than sea
air over land is less dense and rises, creating a pressure gradient of high (sea) to low (land)
112
