Effect of Solar Irradiance Fluctuations on S-NPP Reflective Band CalibrationY. Savranskayaa, J. Wickera, E. Haasa, J. Cardemaa, and F. De Lucciaa

aThe Aerospace Corporation, 2310 E. El Segundo Blvd., El Segundo, CA 900245

SSI VIRGO Blue SSI VIRGO Green SSI VIRGO Red TSI ACRIM3

SSI VIRGO Blue (402nm) 1 0.9037 0.8544 0.7067

SSI VIRGO Green (500nm) 0.9037 1 0.9204 0.7457

SSI VIRGO Red (862nm) 0.8544 0.9204 1 0.7199

TSI ACRIM3 0.7067 0.7472 0.7199 1

I. Total Solar Irradiance (TSI) Fluctuations• Long term (~11 years)• Short Term (days/weeks)•Multiple data sources (from SORCE, VIRGO and ACRIM3) show good agreement

-2850 -2800 -2750 -2700 -2650 -2600 -2550 -2500 -2450-3

-2

-1

0

1

2

3x 10

-3

Time (days since 1 Jan 2013)

Rela

tive V

ariation in S

SI

SORCE blue-1.00985

SORCE green-1

SORCE red-1.0015

VIRGO blue-1.00985

VIRGO green-1

VIRGO red-1.0015

II. Fluctuations in VIIRS F-Factor•VIIRS F-Factor is a radiometric

calibration coefficient• Frequency-domain analysis

revealed similar frequency content for TSI and F-Factor fluctuations

IV. Correlation of TSI and SSI with F-Factor Fluctuations• TSI data generally correlates with F-Factor better than does SSI data•Correlation is best at short wavelengths• Time-domain plots below show strong local correlation (6-wk sliding window) for TSI data (around 0.8 or greater)

III. Solar Spectral Irradiance (SSI) Fluctuations• Two sources of SSI data considered: SORCE SIM

and VIRGO SPM (used here)•Plot below shows region of good agreement for

VIRGO SPM’s three (blue,green,red) spectral bands• Table below shows good correlation between SSI

components and TSI data over region of interest

V. Summary•Based on strong correlation of observed F-Factor fluctuations with solar irradiance fluctuations

(especially for shorter wavelength VIIRS bands), solar variability is a significant source of radiometric fluctuations• SSI data does not show significantly better correlation with F-Factor than TSI data does

EXTENTED ABSTRACT REFERENCES

1. Cardema, J. C., Rausch, K. W., Lei, N., Moyer, D. I., and De Luccia, F. J., “Operational Calibration of VIIRS Reflective Solar Band Sensor Data Records,” Proc. SPIE 8510 (2012).

2. Haas, E., Moyer, D., De Luccia, F., Rausch, K., and Fullbright, J., “VIIRS Solar Diffuser Bidirectional Reflectance Distribution Function (BRDF) degradation factor operational

trending and update,” Proc. SPIE 8510 (2012).

3. Ermolli, I., Mathess, K., Dudok de Wit, T., Krivova, N. A., Tourpali, K., Weber, M., Unruh, Y.C., Gray, L., Langematz, U., Pilewskie, P., Rozanov, E., Schmutz, W., Shapiero, A.,

Solanki, S. K., and Woods, T. N., “Recent variability of the solar spectral irradiance and its impact on climate modeling,” Atmos. Chem. Phys., vol. 13, pp. 3945-3977, 2013.

4. Frohlich, C., and Wehrli, C., “Variability of Spectral Solar Irradiance from VIRGO/SPM Observations,” Physikalish-Meteoroligisches Observatorium Davos, World Radiation

Center internal report, 2002.

0 0.2 0.4 0.6 0.8 1 1.20

0.05

0.1

0.15

0.2

Frequency (cyc/day)

Magnitude o

f T

SI_

SO

RC

E F

FT

norm

aliz

ed b

y n

um

ber

of sam

ple

s

0 0.2 0.4 0.6 0.8 1 1.20

0.2

0.4

0.6

0.8

1

1.2

1.4x 10

-4

Frequency (cyc/day)

Magnitude o

f M

4 F

Facto

r F

FT

norm

aliz

ed b

y n

um

ber

of sam

ple

s

-40 -20 0 20 40 601360.5

1361

1361.5

1362

Time (days since 1 Jan 2013)

Irra

dia

nce (

W/m

^2)

TSI_VIRGO(-4.1)

TSI_ACRIM3

TSI_SORCE

-8000 -6000 -4000 -2000 0 20001357

1358

1359

1360

1361

1362

1363

1364

Time (days since 1 Jan 2013)

Irra

dia

nce (

W/m

^2)

TSI_VIRGO(-4.1)

TSI_ACRIM3

TSI_SORCE

300 500 700 1000 2000 30000.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Wavelength (nm)

Corr

ela

tion(

Sola

r D

ata

, V

IIR

S

F F

acto

r)

M1 M2 M3 M4I1

M5 M6 M7I2

M8 M9 M10I3

M11

VIIRSBands {

VIRGO_blue

VIRGO_green

VIRGO_red

TSI_ACRIM3

VIIRS bands

-240 -210 -180 -150 -120 -90 -60 -30 0 30 60 900

0.2

0.4

0.6

0.8

1

Time (days since 1 Jan 2013)

Local C

orr

ela

tion C

oeffic

ient

Correlation(VIRGO_blue,FM1

)

Correlation(VIRGO_green,FM3

)

Correlation(VIRGO_red,FM7

)

Correlation(TSI_ACRIM3,FM4

)

-0.1

0

0.1

0.2

0.3

% F

luctu

ation

-240 -210 -180 -150 -120 -90 -60 -30 0 30 60 90-0.2

0

0.2

0.4

0.6

0.8

1

Time (days since 1 Jan 2013)

Local C

orr

ela

tion C

oeffic

ient

Correlation(TSI_ACRIM3,FM4

)

FM4

FTSI_ACRIM3

SENSOR/MISSION ACRONYMS

SORCE: Solar Radiation and Climate Experiment

SORCE SIM: SORCE Spectral Irradiance Monitor

VIRGO: Variability of Solar Irradiance and Gravity Oscillations (part of SOHO: Solar and Heliospheric Observatory)

VIRGO SPM: VIRGO 3-channel Sun Photometer

ACRIM3: Active Cavity Radiometer Irradiance Monitor 3 instrument