Shang-Ping Xie & Takeaki Sampe, IPRC, University of Hawaii ... · Shang-Ping Xie & Takeaki Sampe,...

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Mapping high sea winds from space Shang-Ping Xie & Takeaki Sampe, IPRC, University of Hawaii BAMS, in press

Transcript of Shang-Ping Xie & Takeaki Sampe, IPRC, University of Hawaii ... · Shang-Ping Xie & Takeaki Sampe,...

Page 1: Shang-Ping Xie & Takeaki Sampe, IPRC, University of Hawaii ... · Shang-Ping Xie & Takeaki Sampe, IPRC, University of Hawaii BAMS, in press. High Sea Winds • danger to ships ...

Mapping high sea winds from space

Shang-Ping Xie & Takeaki Sampe,

IPRC, University of Hawaii

BAMS, in press

Page 2: Shang-Ping Xie & Takeaki Sampe, IPRC, University of Hawaii ... · Shang-Ping Xie & Takeaki Sampe, IPRC, University of Hawaii BAMS, in press. High Sea Winds • danger to ships ...

High Sea Winds• danger to ships

• intense air-sea exchanges

• enhance upper ocean mixing

� Global mapping of high-wind ( >20 m/s) occurrence using QuikSCAT for 7 years (Sept

–QuikSCAT for 7 years (Sept 1999 – Aug 2006).

Page 3: Shang-Ping Xie & Takeaki Sampe, IPRC, University of Hawaii ... · Shang-Ping Xie & Takeaki Sampe, IPRC, University of Hawaii BAMS, in press. High Sea Winds • danger to ships ...

Dec-Jan-Feb• frequent in wintertime midlatitudes (storm track region)

• less in the (sub-) tropics

winter

Color: High wind frequency (%)

summer

Westerly winds

Storm tracks

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Jun-Jul-Aug• Tropical cyclones do not emerge in climtology

summer

Typhoon

Color: High wind frequency (%)

winter

Typhoon

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� zonal wind

NCEP/NCAR reanalysis (Nakamura et al. 2004)

� low-level

storm track

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Winter North Pacific

SST influence is not clear (front is not so sharp).

several orography-related features

Page 8: Shang-Ping Xie & Takeaki Sampe, IPRC, University of Hawaii ... · Shang-Ping Xie & Takeaki Sampe, IPRC, University of Hawaii BAMS, in press. High Sea Winds • danger to ships ...
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Around Japan

cold air outbreaks off Vladivostok

• high-wind spots, associated with

orography

Strong westerly windafter passage of low (to the east of max. in mean winds)

Contour: SST

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North Atlantic

storm track

South tip of Greenland

storm track

Color: High wind frequency (%) Contour: SST

� Orography (Greenland, Norway, France-“mistral”)

� SST frontal effects (more frequent over warmer waters)

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North Atlantic

2%~17%

� Orography (Greenland, Norway, France-“mistral”)

� SST frontal effects (more frequent over warmer waters)

Color: High wind frequency (%) Contour: SST

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NCEP reanalysis-2*2006 is not included

�orography-related features are not captured well

�SST impact is not clear (land-sea contrast is conspicuous)

Page 13: Shang-Ping Xie & Takeaki Sampe, IPRC, University of Hawaii ... · Shang-Ping Xie & Takeaki Sampe, IPRC, University of Hawaii BAMS, in press. High Sea Winds • danger to ships ...

momentum-mixing mechanism

• lower static stability over warmer waters �

enhanced mixing � increase in downward

transport of momentum to the surface. (Wallace

et al. 1989 etc.)

warmcold

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off Greenland

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JJA

summer

Color: High wind frequency (%)

winter

Page 16: Shang-Ping Xie & Takeaki Sampe, IPRC, University of Hawaii ... · Shang-Ping Xie & Takeaki Sampe, IPRC, University of Hawaii BAMS, in press. High Sea Winds • danger to ships ...

Southern Indian Ocean

warmer water

colder water

warmer water

daily wind vector(u,v)

Color: High wind frequency (%) Contour: SST

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Top 10 list for frequent high winds (annual mean)

Blue: Orographic; Red: SST fronts; Gray shade: near ice edge

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High wind occurrence

QuikSCAT satellite reveals rich variability of high winds.

• Basin scale: storm tracks and the westerlies

• Sub-basin scale: SST and orography• Sub-basin scale: SST and orography

– spatial variations across oceanic fronts

– more (less) over warmer (colder) waters

– coastal orography (cape wind, gap wind)

Sampe and Xie, BAMS, accepted. Preprint, data and images available at

http://iprc.soest.hawaii.edu/~takeaki/highwind/index.html

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Why do high winds occur near major ocean fronts?

Storm growth &surface westerlies

Surface stability

Ocean front

Nakamura et al. (2004)

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Mapping high sea winds from space

Shang-Ping Xie & Takeaki Sampe,

IPRC, University of Hawaii

BAMS, in press