Lecture 2_Local Wind Sources Slides

8/10/2019 Lecture 2_Local Wind Sources Slides

http://slidepdf.com/reader/full/lecture-2local-wind-sources-slides 1/15

LOCAL WIND SOURCES

Part AModule 1 – Wind Energy

8/10/2019 Lecture 2_Local Wind Sources Slides

http://slidepdf.com/reader/full/lecture-2local-wind-sources-slides 2/15

LOCAL WIND SOURCES

Representative situations broken down into two broad

• Winds modified by local topological features – Rain shadow wind (e.g. Foehn, Chinook)

 – Amplification (e.g. Mistral)

• Thermally driven fluid motion on a local scale

 – Sea-land breezes – Mountain top – mountain valley winds

 –  [Katabatic winds]

8/10/2019 Lecture 2_Local Wind Sources Slides

http://slidepdf.com/reader/full/lecture-2local-wind-sources-slides 3/15

RAIN SHADOW WIND (FOEHN W

• Air flow over mountain

• Air with lots of moisture cools

as it rises• Moisture condenses out,

precipitation occurs

• Dense dry cold air flow downleeward slope

• Temperature rises faster fordry air than temperature ofdry air fell

• Result is dry warm wind "Foehn1"

8/10/2019 Lecture 2_Local Wind Sources Slides

http://slidepdf.com/reader/full/lecture-2local-wind-sources-slides 4/15

CHINOOK WIND (CANADIAN PRAI

• Rocky Mountains

• West to east wind• Dense dry air flowsdown lee side ofmountain.

• Here 3353m

decrease in altituderesults in 33.5 oC airtemperature rise

"Chinook wind" by Dhalu

8/10/2019 Lecture 2_Local Wind Sources Slides

http://slidepdf.com/reader/full/lecture-2local-wind-sources-slides 5/15

 AMPLIFIED WIND

Carte du mistra

• Mistral

• Northwesterly wind thatblows through southern

France into the Gulf of Lyon

• Example: Average speeds of

50 km/hr during one day in

November 2008

8/10/2019 Lecture 2_Local Wind Sources Slides

http://slidepdf.com/reader/full/lecture-2local-wind-sources-slides 6/15

MISTRAL (CONT’D)

• Cold air from north

• Complex flowchanneled throughRhone Valley betweenmountains

• Highest speeds southof choke point

Locator Map for Mistr

H

8/10/2019 Lecture 2_Local Wind Sources Slides

http://slidepdf.com/reader/full/lecture-2local-wind-sources-slides 7/15

SOLAR DRIVEN LOCAL WINDS

Wind currents established by uneven solar heating (or

of local surfaces• Examples:

 – Sea and land breezes

 – Mountain top – mountain valley wind

 – Katabatic wind

8/10/2019 Lecture 2_Local Wind Sources Slides

http://slidepdf.com/reader/full/lecture-2local-wind-sources-slides 8/15

SEA AND LAND BREEZESSun on green grass Sun on wate

8/10/2019 Lecture 2_Local Wind Sources Slides

http://slidepdf.com/reader/full/lecture-2local-wind-sources-slides 9/15

DAYTIME SEA BREEZE

• Solar radiation heatsland faster than sea

• Air over land rises

• Rising air cools and sinksover cooler sea

• Sea breeze created ascool air flows to replacerising air on land

8/10/2019 Lecture 2_Local Wind Sources Slides

http://slidepdf.com/reader/full/lecture-2local-wind-sources-slides 10/15

NIGHT LAND BREEZE

• Land cools faster thansea

• Air over sea rises

• Rising air cools and sinksover cooler land

• Land breeze created ascool air flows to replacerising air on sea

8/10/2019 Lecture 2_Local Wind Sources Slides

http://slidepdf.com/reader/full/lecture-2local-wind-sources-slides 11/15

MOUNTAIN TOP DAYTIME

• Upper slopes heated bythe sun

• Adjacent air begins to rise

• Cool air from the valleyfloor moves up to replace

the rising air• Solar driven wind up the

mountain

8/10/2019 Lecture 2_Local Wind Sources Slides

http://slidepdf.com/reader/full/lecture-2local-wind-sources-slides 12/15

MOUNTAIN TOP NIGHT

• Upper slopes cool rapidly

• Adjacent air begins tosink

• Cool air flows down into

the valley floor

• Wind flow down the

mountain

8/10/2019 Lecture 2_Local Wind Sources Slides

http://slidepdf.com/reader/full/lecture-2local-wind-sources-slides 13/15

KATABATIC WINDS• “to flow downhill”

• Air cooled by passing over

Antarctic Ice Sheet• Air over ocean warmer (L)

than air over ice (H)

• Pressure difference driveflow towards ocean

• Dense cold air sinks as itmoves downslope

• Combined effects createquite high wind speeds Katabatic-wind hg" by Han

8/10/2019 Lecture 2_Local Wind Sources Slides

http://slidepdf.com/reader/full/lecture-2local-wind-sources-slides 14/15

LOCAL WIND SOURCES SUMMA

Local topological features can strongly influence global windcreation of local winds.

Two broad categories, each with representative situations:• Global winds modified by local topological features

 –  Rain shadow wind (e.g. Foehn, Chinook)

 –  Amplification (e.g. Mistral)

• Thermally driven (heating or cooling) fluid motion on a lo

 –  Sea-land breezes –  Mountain top – mountain valley winds

 –  [Katabatic winds]

8/10/2019 Lecture 2_Local Wind Sources Slides

http://slidepdf.com/reader/full/lecture-2local-wind-sources-slides 15/15

PHOTO CREDITS

• "Foehn1". Via Wikipedia - http://en.wikipedia.org/wiki/File:Foehn1.png#mediaviewer/File:Foehn1.png 

• "Chinook wind" by Original uploader was Dhaluza at en.wikipedia - Transfered from en.wikipedia. Licens

domain via Wikimedia Commons -

http://commons.wikimedia.org/wiki/File:Chinook_wind.jpg#mediaviewer/File:Chinook_wind.jpg 

• "Carte du mistral" by Vi..Cult... - Données météorologiques du 13 novembre 2008 à midi (carte de Franc

Licensed under Creative Commons Attribution-Share Alike 3.0 via Wikimedia Commons -

http://commons.wikimedia.org/wiki/File:Carte_du_mistral.png#mediaviewer/File:Carte_du_mistral.png

• Locator map for Mistral, US Naval Research Laboratory,

http://www.nrlmry.navy.mil/sat_training/world_wind_regimes/mistral/images/Untitled-2.locatemistral.

• "Katabatic-wind hg" by Hannes Grobe, Alfred Wegener Institute for Polar and Marine Research, Bremerh

Own work. Licensed under Creative Commons Attribution-Share Alike 2.5 via Wikimedia Commons -http://commons.wikimedia.org/wiki/File:Katabatic-wind_hg.png#mediaviewer/File:Katabatic-wind_hg.p