Reducing Uncertainty in Climate Sensitivity with Climatespecific Radiometer

Reducing Uncertainty in Climate Sensitivity with Climate-specific Radiometer Calibration and Requirements Yolanda L. Shea 1, Bruce A. Wielicki 1, Constantine Lukashin 1, Greg Kopp 2, Peter Pilewskie 2, Kurt Thome 3, Gary Fleming 1, Greg Ucker 2, Sunny Sun-Mack 4, Patrick Minnis 4, Mark Zelinka 5, Tyler Thorsen 1 1 NASA Langley Research Center 2 Laboratory for Atmospheric and Space Physics 3 NASA Goddard Space Flight Center 4 Science Systems and Applications, Inc. 5 Lawrence Livermore National Laboratory 1

CLARREO: Decadal Survey Origins Climate Absolute Radiance and Refractivity Observatory CLARREO Mission: Tier 1 recommended mission in 2007 Decadal Survey Purpose: To address critical need of… 1. sufficient accuracy for climate change observations and improved confidence in observing the small climate change signals over decadal and longer time scales and 2. sufficient information content for attribution. 2017 Decadal Survey: Radiance Inter- calibration recommended to address Most Important science priority of reducing climate sensitivity uncertainty. Recommended that NASA execute Program of Record – Including CLARREO Pathfinder 2

CLARREO Pathfinder: Mission Overview Purpose: CLARREO Pathfinder will demonstrate essential Instrument Payload measurement technologies for high accuracy benchmarking and radiance inter-calibration of instruments measuring shortwave radiance. Mission Description Shortwave (SW) Spectrometer to be mounted on the International Space Station (ISS) Nominal 1 -year mission life + 1 year science data analysis Category 3 / Class D Mission Launch Readiness Date: 2023 Spectrally-Resolved Earth Reflectance 3

CLARREO Pathfinder: Mission Objectives Objective #1: Demonstrate High Accuracy SI- Objective #2: Demonstrate Inter- Traceable Radiance Measurements Calibration Capabilities Through on-orbit calibration demonstrate ability to reduce radiance uncertainty by a factor of 4 -8 times compared to the best operational sensors on orbit. Demonstrate ability to transfer calibration other key RS satellite sensors. 4

CLARREO Pathfinder: Uncertainty Requirements Demonstration Parameter Measurement Uncertainty Baseline Requirement Threshold Requirement Spectrally-Resolved Earth Reflectance (350 – 2300 nm): Referenced to spectral solar irradiance ≤ 0. 3% (k = 1) ≤ 0. 6% (k = 1) Spectrally-Integrated Earth Reflectance (350 – 2300 nm): Broadband reflectance with spectral accuracy weighted using global average Earth spectrally reflected energy ≤ 0. 3% (k = 1) ≤ 0. 6% (k = 1) On-Orbit Inter-Calibration: Inter-Calibration with CERES shortwave channel and VIIRS reflectance bands ≤ 0. 3% (k = 1) ≤ 0. 6% (k = 1) 5

CLARREO Pathfinder: Science Obs. Required Mission Operations Spectrally-resolved Earth Reflectance and Radiance High accuracy, geolocated nadir measurements Inter-calibration with CERES and VIIRS Earth-views matched in time, space, viewing angle, and spectral band On-Orbit SI-Traceable Radiance Solar & Lunar Views Additional Mission Opportunities Inter-Calibration of Geosynchronous Imagers Examples: ABI on GOES-16, EUMETSAT’s GERB Inter-Calibration of Low Earth Orbit Imagers Example: Landsat imagers Improved calibration of vicarious calibration sites Spectrally-resolved reflectance over instrumented and non-instrumented sites to calibrate operational and future Earth Science sensors Improved calibration of lunar irradiance Potential ~10 x improvement of current lunar irradiance standard, enabling the moon to be used as on-orbit calibration source for current / future Earth Science instruments 6

CLARREO Pathfinder: Project Status CLARREO Pathfinder was included in the US Fiscal Year (FY) 2018 Budget Project has continued in FY 18 while under Continuing Resolution Currently in extended Phase A of Formulation Project to conduct a delta-System Requirements Review this fall Project successfully conducted SRR/MDR in July 2017; however, programmatics could not be adequately assessed due to uncertainties resulting from the President’s FY 18 Budget Request Anticipate proceeding into a short Phase B of Formulation after the d-SRR Request for Proposal for CLARREO Pathfinder Reflected Solar Payload and Operations prime contract released Sole source procurement to the University of Colorado Laboratory for Atmospheric and Space Physics (LASP) Anticipate awarding prime contract prior to end of FY 18 7

Calibration Uncertainty Impact on Trend Detection Science Question: What measurement and algorithm requirements are needed to detect secular trends in Earth’s climate system and constrain climate model uncertainties? Focus: Reducing uncertainty in cloud property trends and therefore the uncertainty in cloud feedback & climate sensitivity. How long to reduce uncertainty in climate sensitivity by a factor of 2 by constraining cloud property trend uncertainties? Let’s walk through an example using cloud optical thickness (�� c) 8

Cloud Optical Depth Natural Variability Leroy et al. , 2008 Natural Variability Characterization Data: CERES-MODIS (Aqua) cloud retrievals - Minnis et al. , 2011 A “Perfect” instrument would have no uncertainty, but, our ability to detect trends in optical depth would still be limited by natural variability. This isn’t realistic, obviously, so let’s incorporate instrument calibration uncertainty. Shea et al. , 2017 9

Cloud Optical Depth Trend Uncertainty Perfect: Natural Variability Limit CPF+Curr: CLARREO Pathfinder Inter-calibrated with currently operational cloud imagers Curr: Absolute calibration uncertainty of operational cloud imagers Let’s also consider another metric: delay to achieve trend unc. compared to natvar Shea et al. , 2017 10

Cloud Optical Depth Trend Uncertainty & CMIP 5 Remember: How long to reduce uncertainty in climate sensitivity by a factor of 2 by constraining trend uncertainties in cloud optical thickness? We need to link cloud optical depth & climate sensitivity Shea et al. , 2017 11

Cloud Optical Depth Trend Uncertainty & CMIP 5 Gray Shaded Region: 90% Confidence Interval in CMIP 5 climate sensitivity How long to reduce ECS uncertainty by factor of 2 by reducing trend uncertainty in τc? Shea et al. , 2017 12

Constraining Climate Sensitivity How long to reduce ECS uncertainty by factor of 2 by reducing trend uncertainty in τc? Detection Delay Pathfinder: 13 Years 1. 8% (2σ): 24 years Current: 37 years This example illustrates the potential value of reference inter-calibration. Shea et al. , 2017 13

CLARREO Pathfinder: What’s Next? Prime Contract Award for Instrument Build Preparing for delta-SRR/MDR and PDR CLARREO Pathfinder Science Team solicitation expected but date TBD Launch Readiness Date: 2023 Interested in using CLARREO Pathfinder data in the future? -- Please contact me. Dr. Yolanda Shea: Yolanda. shea@nasa. gov 14