1 exploring the potential of ncep’s godas and cfs to diagnose and forecast coastal upwelling for...

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Exploring the Potential of NCEP’s GODAS and CFS to Diagnose and Forecast Coastal Upwelling for California Current Ecosystem

Yan Xue, Boyin HuangClimate Prediction Center

Janine Fisler

University of Maryland at College Park

Acknowledgement: Wayne Higgins, Frank Schwing, Wanqui Wang, David Behringer, Arun Kumar

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Rationale

Coastal upwelling brings nutrients from depth to the surface

Coastal ecosystems flourish in nutrient-rich waters

Monitoring and forecasting upwelling benefits ecosystem and fishery managers

www.oceanjsu.com

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Upwelling in California Current Ecosystem

Ekman Transport ~ along shore

wind stress

Pickett and Paduan, 2003

Huyer, 1983

Ekman Pumping~ wind stress curl

• North of 36˚N upwelling seasonally

• South of 36˚N upwelling year-round

• Onset of Upwelling season progresses from March to July along the coast

• Both onset date and intensity during upwelling season extremely important

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Upwelling Index (UI)(Southwest Fisheries Science Center)

Use NAVY’s FNMOC 3o x 3o and 1ox 1o Sea Level Pressure fields (6-hourly, monthly data since 1967)

Calculate geostrophic winds from SLP

Use along shore wind stress to calculate Ekman transport

SWFSC’s UI is the only routine upwelling product (500 references)

15 Standard Sites

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Global Ocean Data Assimilation System (GODAS)

Background: Assimilates temperature profiles, synthetic salinity,

altimetry into GFDL Modular Ocean Model v.3 Provides oceanic initial conditions for Climate Forecast

System (CFS) 75˚S to 65˚N with resolution of 1˚ by 1˚ 40 vertical levels, with 10m resolution in the upper 200m Pentad temporal resolution Forced by atmospheric Reanalysis 2 (R2) fields

Advantages: Ability to monitor ocean in near-real time (7 day lag) Can use marine fields instead of winds to approximate

upwelling, e.g. vertical velocity at 50-meter depth Coupled with CFS: potential for prediction

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SWFSC vs. GODAS UI: Climatology

Baja

60oN large disagreement South of 39oN large

disagreement

57oN – 39oN good agreement

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Compare both monthly and pentad upwelling

Climatology: 1982-2004 for both data sets

High correlation between 36oN - 57oN

Low correlation north of 57oN and south of 36oN

SWFSC vs. GODAS UI: Anomaly Correlation

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Which index is more accurate?

Few in situ observations to validate indices Difficult to make in situ observations

Problem:

Derive upwelling index using NCEP surface wind analyses (R1, R2, GDAS) similar to SWFSC index

Verify GODAS and SWFSC, NCEP wind-derived indices against with that derived from QuikScat winds,

Approach:

See Poster P1.3 “Multiple Coastal Upwelling Indices for the Western Coast of North America” by Boyin Huang, Yan Xue and Frank Schwing

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Cumulative Upwelling Index: CUI

Following Schwing et al., 2006

Calculate pentad date of climatological onset of upwelling season, “start date” (SD)

Calculate pentad date of maximum climatological upwelling, “maximum date” (MD)

Annually integrate upwelling index from SD to MD

Describe both total and anomalous upwelling

Schwing et al., 2006

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CUI 2005: Delayed Upwelling

48N

45N

39N

36N

33N42N

GODAS GODASSWFSC SWFSC

11(from David Foley, NOAA NESDIS)

2002

Strong Upwelling

2005

Weak Upwelling

SST

Phytoplankton

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CUI 2006: Healthy Upwelling

48N

45N

42N

39N

36N

33N

GODAS SWFSC GODAS SWFSC

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Standardized CUI Anomaly

• CUIA shifted from below- to above- normal in 1998 coincident with PDO shift

• Below-normal years: 88, 93, 97, 05

• Above-normal years: 99, 01, 02, 03, 06

• Poor agreement before 1985

• Below-normal years tend to have positive PDO and NINI3.4

88 9397 05

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Composites for Below-Normal YearsAMJ (1988, 1993, 1997, 2005)

• Positive PDO and warm NINO4 SST

• Anomalous low SLP in NP

• Cyclonic surface wind anom. consistent with SLP

• Upwelling dipole at 40N-45N

W at 50 m depth

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Dep

th

Temp at Depths W at Depths

• Warm SST anom. above 50-meter depth

• Upwelling reaches 300-meter depth at least

• 48N: Upwelling extends 3o offshore

• 42N-45N: Upwelling confined within 0.5o of the coast

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Target AMJ

0 Month Lead

April 1 I.C.

5 members

CFS Forecast

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Target AMJ

1 Month Lead

March 1 I.C.

5 members

CFS Forecast

1 month leadis not as skillful as 0 month lead

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Collaboration between NCEP and SWFSCthrough CTB Proposal

• Use high-resolution CFSRR winds and other NCEP reanalysis winds to improve the accuracy of estimations of coastal upwelling

• Determine skill of CFS to forecast variations in coastal upwelling

• Develop a biologically effective upwelling and transport index (BEUTI) using winds and upper-ocean density structure

• Determine model deficiencies and model requirements for coastal applications

• Real time monitoring and forecasting products of coastal upwelling

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Backup Slides

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0 Month Lead, AMJ

April 1 Initial Condition

5 members

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Critical Factors Controlling Primary Productivity and

Ecosystem Health Timing, intensity, and

duration of Upwelling Stratification of water

column Surface water temperature Turbulence Freshwater input/salinity Position of Jet Stream Light availability, etc. www.abc.net.au

Giant Kelp

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Annual Normalized CUI Anomaly: 1983 CUIA

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Annual Normalized CUI Anomaly: 1986 CUIA

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Annual Normalized CUI Anomaly: 1988 CUIA

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Annual Normalized CUI Anomaly: 1993 CUIA

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Annual Normalized CUI Anomaly: 1997 CUIA

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Annual Normalized CUI Anomaly: 2005 CUIA

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Annual Normalized CUI Anomaly: Disagreements