Reflected Solar Science Summary

1. Reflected Solar Science Summary

2. RS discussion goals • Follow same philosophy as yesterday’s IR discussion • Review • RS science related to benchmarking and reference intercalibration • How to achieve SI traceability • Technical readiness • Requirements • Way forward to writing the RS science summary Reflected Solar Science Studies summary overview

3. Agenda summary • Reflected solar fingerprinting studies: Clear-sky and all-sky B. Collins/D. Feldman (30 min) • Reflected solar radiative kernels & applications to solar fingerprinting Z. Jin (30 min) • Truths status K. Thome for N. Fox (30 min) • D. Young (30 min) • Break 10:15-10:45 • Reflected solar reference intercalibration method and sampling C. Lukashin(45 min) • RS orbit sampling D. Doelling(30 min) • Lunch 12:00-13:30 • Summary of APS on CLARREO Study & review for NASA HQ • Achieving SI traceability in orbit K. Thome(30 min) • Break 14:30-15:00 • Reflected solar instrument requirements, design, traceability, technical readiness, NIST activities K. Thome(60 min) • Science value matrix B. Wielicki(>45 min) • Adjourn 17:15 Reflected Solar Science Studies summary overview

4. Include surface BRDF model (spatial and temporal) for RS benchmark studies • Completion of OSSE studies • Extend to all sky, sun-synch case • Extend to other orbits • Determine difference in globally-averaged zonal, hemispheric-directional reflectance between sun-synchronous orbit and precessing orbit • Nadir view • Annual • Monthly • Goal: Evaluate whether interannual variability varies with orbit selection • Completion of science requirements reports for RS sensor by May 29 (even if only in rough form) • Mission concept study including IR precessing orbit and RS sun-synchronous

5. Summary of RS talks • Climate OSSE study • Modeling effort for a sun-synchronous case at 1:30 pm crossing has been completed • Surface BRDF has been included • Method to account for land-surface changes with time (snow and ice cover) • Consistency checks give confidence that model is being run properly • Future work • Fingerprinting/spectral projection • Signatures of gases and aerosols are tough to pull out except for H2O • Clouds appear to be more straightforward to pull out • Alternate orbits • Pan-spectral techniques • Fingerprinting work • Reflectance better than radiance since normalization allows spectral features to be drawn out. • Developed kernels from currently-available data sets • Success of kernel-based approach demonstrated on the test cases • Perturbing kernels with errors lead to similar results but with more uncertainty in the results • Knowing the cloud fraction in the retrievals reduces uncertainties in other retrievals

6. Summary of RS talks • Intercalibration • Understand number of samples needed to calibrate other sensors to 0.3% accuracy based on factors including • Monthly gain and offset and seasonal polarization sensitivity determination • Time scales and autocorrelation length means individual intercal error can be 1.2% • Noise simulation shows current SNR requirements are sufficient to do the reference intercalibration • Gaps in the ability to sample certain polarization angles and degrees of polarization are not an issue since VIIRS-like sensor will also not sample these combintaions • Sampling and orbital configuration evaluation • CERES data sets normalize the geo-stationary fluxes to fill temporal gaps • Convert fluxes to radiances using CERES angular directional models • Trends identified beyond natural variability with 2 sensors in precessing orbit • Depends on spatial averaging scale • Single sun-synchronous is slightly better than single 90-degree • Two sun-syncs not as good 2 precessingfor annual sampling for 10deg average • Can't get at regional trends with single platform • Further studies to evaluate impact of intercalibration and solar/lunar calibration • Intercalibration does not occur randomly • Early look shows degradation is not significant but need further quantification

7. SI traceability • Improved understanding of methods needed to achieve the 0.3% accuracy requirement • Laboratory work has demonstrated the capabilities needed • Exist multiple approaches to take laboratory capability to orbit • Detector-based • Source-based • Sensor-model methodology • CLARREO will rely on a source-based method (sun) with sensor model to transfer laboratory calibration to orbit • RS instrument overview • Current design going into MCR will be a two-box spectrometer approach • Risk of two-box approach predominantly in characterization/calibration • Mass and cost meet DAC-5 study guidelines • Design meets requirements • Better quantification of accuracy error budget required • Science summary will communicate requirements to community

8. Science summaries • Draft outline of RS Science report follows format of Bruce’s input to TRUTHS proposal • Science Requirements/Value (science & policy) • Science Value and Mission Requirements •  Background • Accuracy required for decadal change observations/rationale • Uncertainty in climate sensitivity dominated by uncertainty in cloud feedback (directly related to decadal changes in cloud radiative forcing) • IPCC Report and expected trends support accuracy requirement – “Back of Envelope Calculations” • Ratio of accuracy of actual observing system relative to perfect climate observing system • Sampling results/Errors in observing system relative to natural variability • Natural variability strong function of time/space scale • Dependence of trend accuracy on CLARREO calibration accuracy

9. Science summary outline • Reference Intercalibration • Background • Matching spectral response to the instrument being calibrated • Time/Space/Angle matching of TRUTHS and the instrument being calibrated • Determining Polarization Dependence of the Instrument Being Calibrated • Determining Spectral Response Change of Broadband Instruments • Determining Orbits and Sampling Required for Reference Intercalibration • Nadir Reflectance Spectral Climate Change Benchmarks • Optical fingerprinting background • Optical fingerprinting as applied to reflected solar spectra • Discussion of radiative kernel method • Results • Calibration approaches • SI traceability • Error budgets • Technical approach of the instrument • Satisfaction of Level 1 & 2 requirements • Risk assessment and mitigations • TRLs

10. Science summary schedule • Preliminary research currently going on • Collecting relevant publications and science reports • Identify probable questions from review boards and science community • Request updated science reports and relevant publications from science team (7/26 deadline for receipt of information) • Finalize outline over next week • Will solicit comments from subset of science team • Meeting with CLARREO project on July 23 • Writing of document • First draft released for comment August 6 • Comments from subset of science team due August 13 • Revision, submission, formatting • Document delivered Aug. 30