statistical downscaling

Bruyere Statistical Downscaling RPSEA 0310

Statistical Downscaling

Cindy Bruyère

NCAR Earth System LaboratoryNational Center for Atmospheric Research

NCAR is Sponsored by NSF and this work is partially supported by the Willis Research Network and the Research Program to Secure Energy for

America

Bruyere Statistical Downscaling RPSEA 0310

Statistical Downscaling

• Look at at Genesis Potential– Mainly focusing on NNRP– CCSM (A2 and A1B scenarios) – NRCM

Bruyere Statistical Downscaling RPSEA 0310

Genesis Potential IndexGP = 105η RH850

30⎛⎝⎜

⎞⎠⎟

3 Vpot70

⎛⎝⎜

⎞⎠⎟

3

1 + 0.1Vshear( )−2

η = absolute vorticity

Vpot = potential intensity

Vshear = shear between 850hPa and 200hPa

Emanuel and Nolan (2004)

Camargo (2007)

Bruyere Statistical Downscaling RPSEA 0310

NA Basin

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

J F M A M J J A S O N D

Number of storms

0

0.2

0.4

0.6

0.8

1

1.2

1.4

GP

cor=0.91

No Storms

Annual Max GP

GP in NNRP Model

Bruyere Statistical Downscaling RPSEA 0310

GP distribution in NNRP

Bruyere Statistical Downscaling RPSEA 0310

w-dev e-dev

dev

gulfNA basin

Basin Gulf Dev East Dev West Dev

Dev + All

Storms

Storms in Gulf

Dev + Storms in Gulf

Max (55-05) .35 .22 .60 .44 .35 .61 .23 .44 Max (80-05) .55 .11 .71 .64 .55 .75 .23 .49 ASO (55-05) .41 .35 .61 .43 .44 .63 .28 .51 ASO (80-05) .60 .24 .74 .63 .66 .79 .27 .58

GP - A Different Approach

Bruyere Statistical Downscaling RPSEA 0310

GP from CCSM (A2)

GP in MDR - NNRP vs CCSM

Bruyere Statistical Downscaling RPSEA 0310

Meridional Avg of GP (15-60W)NNRP

Bruyere Statistical Downscaling RPSEA 0310

CCSM - A2

Meridional Avg of GP (15-60W)NNRP

Bruyere Statistical Downscaling RPSEA 0310

Bruyere Statistical Downscaling RPSEA 0310

Conclusions• Looking at basin wide annual max or ASO average

GP has little value• GP (annual max and ASO average) in development

region is a better measure of storm development in basin

• GP in Gulf has a poor correlation between storms that develop or move through the Gulf area

• GP in CCSM and NRCM runs indicate an increase in GP in the lower latitudes

• More work is needed to develop a better index in the Gulf