Some Experiences and Recent Advances in Surface Radiation

Measurements

Ellsworth G. Dutton

NOAA ESRL Global Monitoring Division

Boulder, Colo. 80305

ells.dutton@noaa.gov

GATE -1974, USCG DallasKirby Hanson’s Met & Radiation Boom

CMDL Baseline ObservatoriesTrinidad Head, CA 40 N

Barrow, Alaska 71 deg. N

American Samoa14 deg. S.

Mauna Loa, Hawaii19 deg. N

South Pole – 90 S

• 1956 to present - solar transmission (Mauna Loa only)• 1975 to present - total downwelling solar irrad• 1976 to present – wideband direct solar – AOD• ~1985 to present – downwelling thermal IR• ~1985 to present – upwelling irradiances• 1995 to present – WCRP BSRN participation

Monthly Averages for 4 Years

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1995 1996 1997 1998 1999Year

W m

-2

Daily Averages for 6 Months

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1997 1997.2 1997.4

Year

W m

-2

Surface Radiation Budget Components, time averaging

LW

LW SW SW

Erie TowerNOAA/BSRN

GMD

1-Minute Averages for 1 day

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400

600

800

1000

75.4 75.9 76.4

Day of Year (GMT, 1997)

W m

-2

Yearly Averages for 14 Years

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1985 1990 1995 2000Year

W m

-2

WMO

IOC

Regions

Oceanic Tropics Desert Polar Coastal Rain forest Agricultural Prairie

E.G. Dutton, 14APR06

Features• Site scientists• 18+ countries• Stand. Specs.

• Long-term• Central archive• Ref. Std. Devlp.

• GRP review• GCOS

Archiving Provisional

Goal:To acquire the highest possible quality, climati-cally-diverse, surface-based radiation measurements for climate & remote sen. applications

Data Applications

• GCM comparisons• Satellite prod. validation• Regional climatologies• Radiation budget apps.• Radiation model testing

Measurements• Direct & diffuse solar*• Downward infrared *• Upwelling irrad.• PAR & UV• Aerosol optical depth• Surface meteorology*• Upper air met.• Sky imagery, cloud height* all sites 1992 – 2006+

NOAA / BSRNInstrument close-ups

Surface-based broadband radiation measurement issues addressed by BSRN

• Spatial representativeness of data• Extent of climatic regimes sampled• Calibration references, SW diffuse & LW• Component sum vs. global SW • Thermal errors in thermopile sensors• Effects and benefits of artificial ventilation• UV, PAR, albedo, aerosol O.D.• Specifications and Operations Manual

BSRN (and the world) needs more in situ, representative, oceanic surface

radiation measurements

• BSRN is an international cooperative project of the World Climate Research Program and GEWEX and as such has NO central funding, only volunteers generally working as their country’s radiation experts and representatives to WMO/WCRP are involved – these folks are called BSRN Site Scientists with their own national or whatever funding.

• BSRN requires adherence to its specifications.

WARNING:

BSRN has a new (2004) Oceanic Working Group

• Issues – platforms, measurement accuracy (available and required), moving sites, instrument orientation, obstructions, sea spray+, lack of upper air soundings…

• Assess the required accuracy needed in interesting very data-poor regions to contribute to satellite and climate model projects

• Revisit BSRN specifications and consider drafting an oceanic version

• Inventory candidate platforms

• Recruit potential participants – encourage improvements

• Evaluate of impact on stated requirement for long-time series and other complications

• Ken Rutledge NASA/Langley chair (Chesapeake Light House SS)

Contact me if interested -- ells.dutton@noaa.gov

188 pp

Step 1.Assess current accuracyand that required to contributeto atmospheric research.

Step 2. Figure out how to get there.

The BSRN approach

Philipona and Marty

Improving Ground-based Radiation Meas. Calibration Standards

Improvements in Pyrgeometer (Downward IR) Accuracy

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35

1988 1993 1995 1998 2001 TargetYear

wat

ts m

eter

-2

Routine Field Operations

Ideal Operations

Calibration Reference

E.G. Dutton, 2002

Sources of Uncertainty

Wm-2

Michalsky et al 2004, 2006

Step 3. Get there.

Candidate Reference, ASR

PYRGEOMETERS

IPASRC-I Oklahoma ARM/SGP

Philipona et al., 2001/Marty et al., 2003

IR Radiometer IntercomparisonsD

iffe

ren

ce R

elat

ive

to P

rop

osed

Ref

. Mea

s. (

Wm-

2)

Observations Models

BSRN-ARM/CMDL

1999 Mid-West US, 270-300 W m-2

2001 Arctic – Barrow, 120-145 W m-2

Michalsky et al., 2005

Clear-sky surface radiative closure, diffuse and direct

Average of 30 cases on 13 days

S. Kato C. Gueymard

Avg. (337)BSRN (344)

Circa 2005

GCM modelsglobal means M. Wild 2001& 2005

Over last 6 years climate models approach BSRN downwelling IR results

BSRN (344 W m-2)

Model Avg. (329)

Circa 1999

GCM models (global means)

Satellite Results:Satellite Results:

Downward Surface SWFlux (Wm-2)

Downward Surface LWFlux (Wm-2)

GEWEX SRBPaul Stackhouse, NASA/Langley

Long-term Annual AveragesLong-term Annual Averages

Figure 13. Scatter plots for all the available monthly mean surface fluxes from BSRN and corresponding values from ISCCP-FD: (a) S9s and (b) L9s in Wm!2. Statistics from the plot are given in Table 7a.

Y. Zhang, W. B. Rossow, A. A. Lacis, V. Oinas, M M. Mishchenko, accepted JGR, 2004

ISCCP model

BS

RN

• LW, monthly avg • SW, monthly avg

BSRN Comparison to a new satellite product

SRB Validation: Reanalysis, CERES Surface-only fluxes (time averaged)

Bias SDev RMS R^2 Bias SDev RMS R^2GEWEX SW/LW 5.55 10.89 12.22 0.9698 -4.05 5.59 6.90 0.9903GEWEX QC SW/LW 5.59 11.72 12.98 0.9651 -2.07 6.80 7.11 0.9894CERES Surface-only 3.35 8.55 9.18 0.9840 1.75 9.89 10.04 0.9659NCEP R2 22.52 26.93 35.11 0.8058 -5.76 13.30 14.49 0.9451ERA-40 -2.12 19.17 19.29 0.9186 1.43 6.22 6.38 0.9885

SourceSW LW

BSRN sites: Bermuda, Billings, Florinapolis, Goodwin Creek, Kwajalein, Manus, Tateno

BSRN v. SW Estimates (Feb, Jul 1998)

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Measured Flux

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GEWEX QC SW

GEWEX SW

NCEP

ERA-40

BSRN v. LW Estimates (Feb, Jul 1998)

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Measured Flux

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GEWEX QC LW

GEWEX LW

NCEP R2

ERA-40

Summary• Surface-based surface solar and infrared radiation

measurements are of considerable value today.• BSRN has pursued improving the accuracy and confidence of

surface irradiance obs.• Work is ongoing to establish recognized and lasting radiation

reference standards.• An IPCC Radiative Flux Assessment is being prepared.• While BSRN was original intended for fixed-site, ground-based

observations, a substantial need for open-ocean obs has emerged and BSRN is attempting to address that need.

• Potential BSRN-like shipboard radiation measurements include: downwelling solar and longwave irradiances, direct and diffuse solar, Aerosol optical depth, cloud imagery, meteorology, PRT SST…

The End

NOAA Station data x-correlated with NASA / ISCCPannual averages, total surface solar 1984 - 2000

Units are X-Corr. Coef. / S. E.

▲

▲

▲

SMO

▲

▲

BLD

E. Dutton et al., 2006

BSRN Operational Measurement Quality

LW Broadband (pyrgeometer)

5 - 7 (2%) 5 3 -- 5 3 -- 5 3 -- 5 ?? ---

SW Broadband Global (direct+diffuse, pyranometer)

25+ (4-5%) 8 -- 20 5 -- 15 5 -- 15 5 -- 15 ??up to -3%

SW Broadband Direct (NIP)

5 - 15 (1.5%) 1% or 2 1% or 2 1% or 2 1% or 2 ?? ---

SW Broadband Diffuse (shaded pyranometer)

5 -- 7 (3-4%) 5 -- 15 5 -- 15 5 -- 12 5 -- 12 ??up to -10

SW Broadband Total (shaded pyranometer +

NIP)10 -- 15 (3.0%) 5 -- 15 5 -- 15 5 -- 12 5 -- 12 ??

up to -10

RMS Uncertainties for Radiative Measurements (Ohmura et al, 1998, BAMS; Michalsky et al., 1998; Shi and Long, 2002, Dutton et al., 2001; Ells Dutton personal comm.)

Thermal Offset

1 Month

(W m-2)

1 Year

(W m-2)

10 Years

Quantity (Instrument)

1 Minute Avg. (1 Hz sampling)

(W m-2)

1 Hour

(W m-2)

1 Day

(W m-2)

Compiled by Paul Stackhouse NASA/SRB