EAE2111 - Topic 2 - Wk 3 Flashcards

Question 1

Q

What is anabatic wind flow?

Answer

A

<ul><li>Occurs during the day </li><li>Rₙ is strongly positive and much of the excess energy is dissipated by convection (H) </li><li>Although eddies are generally directed up and away from the slope, there is a general upslope component to flow that develops</li></ul>

_{EAE2111 3aa}

Question 2

Q

What is katabatic wind flow?

Answer

A

<ul><li>Occurs at night </li><li>Rₙ is negative because of a lack of solar radiation </li><li>Layer of air adjoining the soil cools due to longwave emission and becomes more dense than the surrounding air </li><li>Cool, dense air flows downslope under the influence of gravity</li></ul>

_{EAE2111 3ab}

Question 3

Q

Describe

S simple valley (anabatic) wind development?

Answer

A

<ul> <li>After sunrise, anabatic flow begins. Flow stronger in a valley with a northerly/southerly aspect in SH/NH</li> <li>To maintain continuity, a closed circulation develops, with descending air motion in the valley centre.</li> <li>After time, whole valley atmosphere becomes warmed by this process.</li> <li>Eventually, the valley atmosphere becomes much warmer than air at a similar level over adjoining plains, so a plain to mountain airflow begins up the valley i.e. Anabatic winds</li></ul>

<div>As a result of this circulation and the lifting of moist air clouds often form above the ridge tops.</div>

_{EAE2111 3ac}

Question 4

Q

Describe

Simple mountain (katabatic) wind development?

Answer

A

<ul> <li>Night, circulation works in reverse.</li> <li>After sunset, katabatic flow.</li> <li>When sufficient cold air builds up in the valley, flow will commence at low levels out of the valley - called mountain wind.</li> <li>A cross-valley circulation develops to maintain continuity.</li></ul>

_{EAE2111 3ad}

Question 5

Q

What is the impact of overlying winds?

Answer

A

Cold air drainage leads to ponding in valleys

_{EAE2111 3ae}

Question 6

Q

What is a polynya?

Answer

A

A polynya is generated as strong katabatic winds push sea ice away from the land

_{EAE2111 3af}

Question 7

Q

Surface motion measurement

What are rotating cup anemometers?

Answer

A

<ul> <li>Located in most of the Bureau of Meteorology's </li> <li>Automatic Weather Stations (AWS). </li> <li>Rotation rate of the cups gives an indication of wind speed. </li> <li>Direction is given by the weather vane. </li> <li>Both measurements operate independentlyTypically measured at a height of 10m (BoM) over land to have a consistent impact of surface friction.</li> <li>Measurements typically returned: wind direction, maximum wind gust and daily mean wind speed.</li></ul>

<div>Roughly 1700 locations around Australia</div>

_{EAE2111 3ag}

Question 8

Q

Surface motion measurement

What are vane anemometers?

Answer

A

<ul><li>Rotation rate of the propeller gives an indication of wind speed. </li><li>Direction is given by the weather vane </li><li>Weather vane required for accurate measurement of winds</li><li>These are used at ocean mooring sites. </li><li>Over water the height is typically 4m, but can be converted to 10m using formula.</li></ul>

_{EAE2111 3ah}

Question 9

Q

Surface motion measurement

What are ultrasonic anemometers?

Answer

A

<ul><li>Measure wind speed based on the time of flight of sonic pulses between pairs of transducers. </li><li>Measurements from pairs of transducers can be combined to yield a measurement of velocity in 1-, 2-, or 3-dimensional flow. </li><li>The spatial resolution is given by the path length between transducers, which is normally between 10 and 20 cm. </li><li>Ideal for turbulence measurements.</li></ul>

_{EAE2111 3ai}

Question 10

Q

Surface motion measurement

What is doppler radar?

Answer

A

<div>AWS data are good, but relatively sparse if we wanted to monitor a sea breeze front, or an incoming cold front?</div>

<div>Doppler radars take measurements by sending out electromagnetic waves, and monitoring what gets reflected back to the radar.</div>

<div>They can measure:</div>

<ul> <li>Rainfall</li> <li>Wind direction and speed (relative to the radar)</li></ul>

<div>They also have a good spatial resolution… </div>

<div>Wind direction and speed are measured relative to the radar, so you have towards or away from radar directions.</div>

Doppler radars do not measure winds at the surface._{EAE2111 3aj}

Question 11

Q

Surface motion measurement

What are the types of remote sensing?

Answer

A

Remote sensing can be passive or active, both types detect emission, reflection or scattering of energy. This can tell us about the object.

<div>Passive remote sensing measures energy that is only naturally available </div>

<div>Examples: most satellites, Photography </div>

<div>Active remote sensing provides an energy source for illumination </div>

<div>Examples: Radar, Lidar and some satellites</div>

Satellites infer surface stress from scatterometer measurements of small-scale surface roughness, which can be translated to equivalent 10 m wind. Winds can only be measured over the ocean_{EAE2111 3ak}

Question 12

Q

Upper level motion measurement

What is a pilot balloon?

Answer

A

<ul> <li>Fill a large balloon with Helium, </li> <li>Release the balloon </li> <li>Track with two theodolites that are far apart & search for the intersection.</li></ul>

<ul> <li>Assume an assent rate & measure with one theodolite</li></ul>

_{EAE2111 3al}

Question 13

Q

Upper level motion measurement

What is a radiosonde?

Answer

A

<div>Much like a PiBall (pilot balloon)</div>

<ul> <li>Fill a large balloon with Helium,</li> <li>Release the balloon</li> <li>Rather than physically tracking the balloon, it has a package attached that measures location with GPS (which can be used to calculate wind speed), along with temperature, atmospheric moisture and pressure</li></ul>

_{EAE2111 3am}

Question 14

Q

Describe

Cloud measurement?

Answer

A

Measured visually at 9am and 3pm at particular locations.

<ul><li>Satellites images of clouds utilise infrared radiation emitted from all things to generate images (passive remote sensing). </li><li>Clouds tend to be cooler than the ground or sea below so are visible on the images </li><li>The temperature of clouds is associated with their height, so highlighting certain temperature ranges is useful for estimating the height of the observed clouds. </li><li>Himawari </li><li>geostationary satellite located over tropics with good view of Australia</li></ul>

_{EAE2111 3an}

Question 15

Q

Rainfall Measurement

Answer

A

<ul> <li>Rain gauge measurements</li> <ul> <li>Largely 24 hour totals of rainfall accumulation (occasionally 3 hour totals)</li> <li>Notice the location, near to the ground.</li> </ul> <li>Doppler radars</li> <ul> <li>Dopler is a great tool to monitor the movement of weather systems.</li> </ul> <li>The Global Precipitation Measurement (GPM) Microwave Imager Instrument </li> <ul> <li>A multichannel, conical-scanning, microwave radiometer </li> <li>serves an essential role in the near global-coverage and frequent-revisit-time requirements of GPM.</li> </ul></ul>

_{EAE2111 3ao}

Question 16

Q

Climate zones - What would we expect given we have learned?

Tropics

Answer

A

<ul><li>Around 15°S to 15°N </li><li>Warm all year </li><li>no seasons </li><li>Humid </li><li>Convection due to surface heating </li><li>Ascending branch of Hadley Cell (ITCZ) </li><li>Light, easterly winds </li><li>Rainforests </li><li>Warm sea-surface temperatures </li><li>Example: Singapore</li></ul>

Rainforests are largely located under the rising branch of the Hadley Cell, known as the Inter-Tropical Convergence zone_{EAE2111 3ap}

Question 17

Q

Climate zones - What would we expect given we have learned?

Sub-tropics?

Answer

A

<ul><li>Around 25°S/N to 35°S/N </li><li>Descending branch of the </li><li>Hadley Cell leads to subtropical ridge </li><li>High pressure at surface </li><li>Light winds </li><li>Hot summer, mild-warm winter </li><li>Little precipitation </li><li>Hot deserts </li><li>Example: Coober Pedy, SA</li></ul>

Deserts are largely located under the sinking air of the Hadley Cell_{EAE2111 3aq}

Question 18

Q

Climate zones - What would we expect given we have learned?

Mid-Latitudes

Answer

A

<ul><li>Around 40°S/N to 55°S/N </li><li>Prevailing westerlies and longwave pattern u Systematic movement of highs, lows and fronts </li><li>Cool </li><li>mild in summer; cold in winter </li><li>Highly changeable year around (fronts) </li><li>Similar precipitation year around </li><li>Example: Southern Tasmania</li></ul>

_{EAE2111 3ar}

Question 19

Q

Climate zones - What would we expect given we have learned?

Polar

Answer

A

<ul> <li>Poleward of 65°S/N</li> <li>Prevailing easterlies</li> <li>High pressure, descending, cold air</li> <li>Cold in summer, 24h sunlight</li> <li>Even colder in winter, 24h darkness</li> <li>Dry all year (Antarctica driest place on Earth)</li> <li>Example: Antarctica, Arctic</li></ul>

_{EAE2111 3as}

Question 20

Q

Climate zones - What would we expect given we have learned?

What is the tropical – sub-tropical shoulder?

Answer

A

<ul><li>Around 15°S/N to 25°S/N </li><li>Tropical influences in summer; extratropical (i.e. non-tropical) influences in winter </li><li>Easterlies in summer; light winds in winter </li><li>Warm, wet, humid summers </li><li>Dry, moderate winters </li><li>Example: Toowoomba, Qld</li></ul>

_{EAE2111 3at}

Question 21

Q

Climate zones - What would we expect given we have learned?

What is the sub-tropical – mid-latitude shoulder?

Answer

A

<ul><li>Around 35°S/N to 40°S/N </li><li>Sub-tropical influences in summer; mid-latitude influences in winter </li><li>High pressure in summer; fronts, longwave pattern and prevailing westerlies in winter </li><li>Warm </li><li>hot summers; cool winters </li><li>More precipitation during winter than summer </li><li>Example: Melbourne</li></ul>

_{EAE2111 3au}

Question 22

Q

Climate zones - What would we expect given we have learned?

What is the mid-latitude – polar shoulder?

Answer

A

<ul> <li>Around 55°S/N to 65°S/N</li> <li>Prevailing westerlies and longwave pattern</li> <li>Systematic movement of highs, lows</li> <li>Sensitive to location of polar front i.e. very changeable</li> <li>Cool - mild in summer; cold to very cold in winter</li> <li>Similar precipitation year around</li> <li>Extent of tree line/tundra</li> <li>Example: Canada/Alaska, Scandinavia</li></ul>

_{EAE2111 3av}

Question 23

Q

Climate zones - What would we expect given we have learned?

Why are there are differences?

Answer

A

<ul><li>Northern and southern hemisphere behaviour different due to land mass differences </li><li>Land heats/cools much faster than oceans </li><li>Topography and land-sea distriution can alter circulation</li></ul>

_{EAE2111 3aw}

Question 24

Q

What is the general circulation and climate?

Answer

A

<div>Can broadly place climate into categories according to the general circulation</div>

<div>Polar: Cold, dry, easterly winds</div>

<div>Mid-Latitude: Cool, wet, fronts, westerly winds, windy</div>

<div>Sub-Tropical: Dry year-round, hot, light winds, high pressure</div>

<div>Tropical: Precipitation year-round, warm, humid, convective, ITCZ, easterly winds</div>

<div>Mirrors around the equator </div>

_{EAE2111 3ax}

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EAE2111 - Topic 2 - Wk 3 Flashcards

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