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Downbursts and dust storms

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Review of last lecture

1. 2 types of mesoscale convective systems

2. Structure of MCCs

3. Structure of squall lines: four components

4. Flash floods and mudslides

1. Derechos

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Different downbursts

620 miles or 1000 km

62 miles or 100 km

6.2 miles or 10 km

0.62 mile or 1 km

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Microburst Downbursts with diameteres

of less than 4km (2.5mi)called microbursts

is a very localized column ofsinking air, producing

damaging divergent andstraight-line winds at thesurface that are similar to,but distinguishable from,tornadoes, which generallyhave convergent damage.

can produce dangeroussituations at airports, as theyimpede air travel.

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Video: Microburst

http://www.youtube.com/watch?v=NT3YbuGHfC4

http://www.youtube.com/watch?v=NT3YbuGHfC4http://www.youtube.com/watch?v=NT3YbuGHfC4http://www.youtube.com/watch?v=NT3YbuGHfC4http://www.youtube.com/watch?v=NT3YbuGHfC4

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Development of microburst

Three stages: Contact, Outburst, Cushion

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Structure of a microburst

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Two types of microburst

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Microburst and air travel

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Fatal crashes or aircraft incidents dueto microbursts

A BOAC Canadair C-4 (G-ALHE), Kano Airport - 24 June 1956. A Malv Ilyushin Il-18 (HA-MOC), Copenhagen Airport 28 August 1971.Eastern Air Lines Flight 66 Boeing 727-225(N8845E), John F. KennedyInternational Airport 24 June 1975Pan Am Flight 759 Boeing 727-235 (N4737), New Orleans International Airport 9 July 1982Delta Air Lines Flight 191 Lockheed L-1011 TriStar (N726DA), Dallas/FortWorth International Airport 2 August 1985Martinair Flight 495 McDonnell Douglas DC-10 (PH-MBN), Faro Airport 21December 1992

USAir Flight 1016 Douglas DC-9 (N954VJ), Charlotte/Douglas International Airport 2 July 1994Goodyear Blimp GZ-20A (N1A, "Stars and Stripes"), Coral Springs, Florida 16 June 2005Bhoja Air Flight 213 Boeing 737-200 (AP-BKC), Islamabad International

Airport, Islamabad, Pakistan- April 20 2012

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Haboobs Very strong horizontal winds over desert regions create sandstorms

called haboobs (from the Arabic word meaning wind ). Occur regularly in arid regions throughout the world.

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Video: Haboobs

http://www.youtube.com/watch?v=LGDvBk4knF0

http://www.youtube.com/watch?v=LGDvBk4knF0http://www.youtube.com/watch?v=LGDvBk4knF0http://www.youtube.com/watch?v=LGDvBk4knF0http://www.youtube.com/watch?v=LGDvBk4knF0

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Global impact of dust storms

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Factors contributing to dust storms

DesertificationDrying of global soil moisture

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Desertification

Caused mainly behuman activities andclimate change

Is one of the mostsignificant globalenvironmental problems

About a billion peopleare under threat

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Global desertification vulnerability

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Drying of global soil moisture

The Palmer drought severity index (PDSI) wasdeveloped by Wayne Palmer in the 1960s anduses temperature and rainfall information in amodel to determine dryness of soil moisture.

is most effective in determining long termdrought (a matter of several months) and is notas good with short-term forecasts (a matter ofweeks).It uses a 0 as normal, and drought is shown interms of minus numbers.

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PSDI for US in December 2011

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Change of PSDI in the last 100 years

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Video

A movie s depiction of dust storm:http://www.youtube.com/watch?v=B4sNGmDBLWg at 1 33 59-1:35:00

http://www.youtube.com/watch?v=B4sNGmDBLWghttp://www.youtube.com/watch?v=B4sNGmDBLWghttp://www.youtube.com/watch?v=B4sNGmDBLWghttp://www.youtube.com/watch?v=B4sNGmDBLWghttp://www.youtube.com/watch?v=B4sNGmDBLWghttp://www.youtube.com/watch?v=B4sNGmDBLWghttp://www.youtube.com/watch?v=B4sNGmDBLWghttp://www.youtube.com/watch?v=B4sNGmDBLWghttp://www.youtube.com/watch?v=B4sNGmDBLWghttp://www.youtube.com/watch?v=B4sNGmDBLWghttp://www.youtube.com/watch?v=B4sNGmDBLWg

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Summary1. 3 types of downbursts.

2. 3 stages of microburst development. 2 types ofmicrobursts.

1. Haboobs.

2. Global desertification.

3. What is PDSI? Which two variables is PDSI dependenton? How has the PDSI been changing in the lastcentury?