V2 Composite Solar Spectral
Irradiance Data Product
Matthew DeLand1, Sergey Marchenko1, Linton Floyd2,
Ramaswamy Tiruchirapalli1
1SSAI/NASA
2SSRC

GSFC

3rd SIST Science Meeting, Lanham, MD 8-9 May 2018

Introduction
• Project goal is to improve and extend composite
solar spectral irradiance (SSI) data set created by
DeLand and Cebula [2008] (V1).
• New irradiance data sets are needed to extend
this product from July 2005 to the present.
• This presentation will review the development of
a new SBUV/2 data set for the V2 composite SSI
product.
• Examples of the preliminary merged V2
composite SSI product will be shown.
• Reconciling different data sets at transition points
(both spectral and temporal) is a remaining issue.

Timeline of New SSI Data

Additional SBUV/2 Irradiance Data
• NOAA-16 daily spectra (170-400 nm) cover Mar 2001 –
Sep 2007 [+ spring 2008] before significant orbit drift
issues appear (shadowing of solar diffuser).
• Use same long-term correction approach as applied to
NOAA-9 and NOAA-11 in V1 composite SSI data set:
– Use UARS SUSIM reference spectra in place of SSBUV
flights as absolute reference
– Create “Day 1” ratio between NOAA-16 and SUSIM to
remove calibration bias
– Compare concurrent NOAA-16 observations to reference
spectra on selected dates to establish benchmarks for
correction
– Create smooth fits (wavelength, time) for degradation
function to correct SBUV/2 data

SUSIM Solar Change Estimates

NOAA-16 “Day 1” Ratio vs. SUSIM

NOAA-16 Coincident Ratio vs. SUSIM

NOAA-16 Degradation Fit – samples

NOAA-16 Time Series – 200-205 nm

NOAA-16 vs. SUSIM – 200-205 nm
NOAA-16 data for composite

Structure of V2 Composite SSI Product
• Start using NOAA-16
data in March 2005
to help fill SUSIM
data gaps near end of
mission.
• Transition to OMI
data in January 2007.
• Fill gaps at shorter
wavelengths using
proxy models and
scaled Bremen
composite Mg II
index.
• Fill data for 400-500
nm before OMI?

V2 Merged Data – 155 nm

V2 Merged Data – 230 nm

V2 Merged Data – 310 nm

V2 Merged Data – All Wavelengths

V2 Transition – Case 1

V2 Transition – Case 2

Next Steps for Project
• Resolve offsets at transition locations.
• Ensure that interpolation for small gaps is
handled correctly.
• Determine format for uncertainty estimates.
• Provide preliminary composite data set for
comments.
• Complete manuscript for journal paper.