2nd RASM Workshop2012 Spring

Brandon J. FiselIowa State University

Department of Geological and Atmospheric Sciences

Monterey, CA 14-18 May

OVERVIEW

2nd RASM May 2012

Sea ice – atmosphere interactions recent, rapid sea-ice decline

Model circulation regimes exist Goal

sea-ice area changes affects persistent circulation regimes implications for predictability of future

atmospheric circulation seasonal T extremes

METHODOLOGY

2nd RASM May 2012

WRF-ARW 3.1 CORDEX domain

50 km resolution

Analysis region

METHODOLOGY (CONT…)

2nd RASM May 2012

ECMWF (ERA-Interim); 6-hr SST and sea ice; prescribed; 12-hr

1 Ensemble; 16 members June – December, 2007 1 or 2 regimes Model-based clustering

model selection; BIC model fit; penalty for model

complexity Time windows

> synoptic time frame; 7 & 11 days

METHODOLOGY (CONT…)

2nd RASM May 2012

Seasonal T extremes JJA and OND; 1st and 99th percentile regions; ANC, AS1 and SC land points only

ANCAS1SC

REGIMES

2nd RASM May 2012

2 regimes; differing trends

2 regimes; significantlyseparated

1 regime

REGIMES (CONT…)

2nd RASM May 2012

significantly separated

a) high MSLPb) low MSLP

differingtrends

c) high MSLPd) low MSLP

REGIMES (CONT…)

2nd RASM May 2012

Model variabilityMonth 75th – 25th [hPa]June(15-30) 6.1July 4.9August 8.1September 5.7October 10.1November 9.0December 9.8

< 8 hPa

> 8 hPa

REGIMES (CONT…)

2nd RASM May 2012

Month 7-Day 11-DayJune(15-30) 93% 100%July 71% 87%August 84% 97%September 33% 30%October 74% 94%November 63% 83%December 96% 100%

BIC2 > BIC1

REGIMES (CONT…)

2nd RASM May 2012

Regime streaks

JJA: tendency to remain in one mode of regime behavior

Slower evolving atmospheric flow

Season Mean length [days]JJA (7-Day) 7.9JJA (11-Day) 24.0OND (7-Day) 6.0OND (11-Day)

15.0

REGIMES (CONT….)

2nd RASM May 2012

2-Regime JJAHow persistent do days fall into a 1 or 2-regime window?0 1 2 3 4 5 6 7

02468

1012141618

Persistence [days]

Freq

uenc

y

0 1 2 3 4 5 6 70

5

10

15

20

25

30

35

Persistence [days]

Freq

uenc

y

2-Regime ONDMore persistent days a calendar date falls into

a 2-regime window.

EXTREMES

2nd RASM May 2012

2-Regime JJA [1st P]Cold extremes preferred in 2-regime behavior.

2-Regime OND [99th P]

Warm extremes preferred in 1-regime behavior.

0 1 2 3 4 5 6 702468

101214161820

Persistence [days]

Extr

emes

day

-1

0 1 2 3 4 5 6 70

20406080

100120140160180200

Persistence [days]

Extr

emes

day

-1

SUMMARY

2nd RASM May 2012

Multiple dynamic regimes persistent, multiple regimes (JJA) less persistent, multiple regimes

(OND) persistent, 1-regime (September)

Implications changing sea-ice area affects regime

persistence future predictability of atmosphere future decline in summer sea ice more persistent regime behavior?

SUMMARY (CONT…)

2nd RASM May 2012

Temperature extremes tendency for more cold (warm)

extremes with 2(1)-regime behavior Future work

regimes: coupled model; modeled vs. prescribed SST’s; similar behavior?

T extremes: 20-year simulation (uncoupled WRF, RASM)

change in energy/moisture budgets allow for a more extreme, future arctic?

QUESTIONS

2nd RASM May 2012

E-mail: bjfisel@gmail.com

?

Ensemble MSLPModel EstimatedMean95% CI

REGIMES

REGIMES

REGIMES

REGIMES

REGIMES

REGIMES

REGIMES

REGIMES

REGIMES

REGIMES

REGIMES

REGIMES

REGIMES

REGIMES

2nd RASM May 2012

More persistent 1-regime behavior vs. JJA and OND.

0 1 2 3 4 5 6 70

2

4

6

8

10

12

Persistence [days]

Freq

uenc

y

2-Regime September

EXTREMES

2nd RASM May 2012

0 1 2 3 4 5 6 705

101520253035404550

Persistence [days]

Extr

emes

day

-1

2-Regime Sept. [99th P]

Warm extremes preferred in 1-regime behavior. 0 1 2 3 4 5 6 7

0

5

10

15

20

25

30

35

40

45

Persistence [days]

Extr

emes

day

-1

2-Regime Sept. [1st P]

Cold extremes preferred in 2-regime behavior.